Using Parallel Maya


This guide describes the Maya features for accelerating playback and manipulation of animated scenes. It covers key concepts, shares best practices/usage tips, and lists known limitations that we will aim to address in subsequent versions of Maya.

This guide will be of interest to riggers, TDs, and plug-in authors wishing to take advantage of speed enhancements in Maya.

If you would like an overview of related topics prior to reading this document, check out Supercharged Animation Performance in Maya 2016.

Key Concepts

Starting from Maya 2016, Maya accelerates existing scenes by taking better advantage of your hardware. Unlike previous versions of Maya, which was limited to node-level parallelisms, Maya now includes a mechanism for scene-level analysis and parallelization. For example, if your scene contains different characters that are unconstrained to one another, Maya can evaluates each character at the same time.

Similarly, if your scene has a single complex character, it may be possible to evaluate rig sub-sections simultaneously. As you can imagine, the amount of parallelism depends on how your scene has been constructed. We will get back to this later. For now, let’s focus on understanding key Maya evaluation concepts.

At the heart of Maya’s new evaluation architecture is an Evaluation Manager (EM), responsible for creating a parallel-friendly description of your scene, called the Evaluation Graph (EG). The EM schedules EG nodes across available compute resources.

Prior to evaluating your scene, the EM checks if a valid EG graph exists. The EG is a simplified version of the Dependency Graph (DG), consisting of DG nodes and connections. EG connections represent node-level dependencies; destination nodes employ data from source nodes to correctly evaluate the scene. A valid EG may not exist or become invalid for various reasons. For example, you may have loaded a new scene and no EG may have been built yet, or you may have changed your scene, invalidating a prior EG.

Maya uses the DG’s dirty propagation mechanism to build the EG. Dirty propagation is the process of walking through the DG, from animation curves to renderable objects, and marking DG node attributes as requiring evaluation (i.e., dirty). Unlike previous versions of Maya, that propagated dirty on every frame, Maya now disables dirty propagation once the EG exists, reusing the EG until it becomes invalid.

With dirty propagation disabled, computing a given scene frame involves walking the EG, scheduling EG nodes, and evaluating them. Because the EG encodes node-level dependencies, when evaluating a given EG node, you are guaranteed that inputs from dependent nodes have already been calculated. This further enables pipelining of some operations. Specifically, when EG nodes have no dependents, it is possible to immediately initiate additional processing (e.g., rendering) since we are guaranteed that no downstream nodes require computed results.

Tip. If your scene contains expression nodes, that use getAttr, the DG graph will be missing explicit dependencies. This will result in an incorrect EG. Expression nodes also reduce the amount of parallelism in your scenes (see Scheduling Types for details). Consider removing getAttr from expressions and/or using utility nodes.

Depending on your scene, the EG may contain circular node-level dependencies. If this is the case, the EM creates node clusters. At scene evaluation time, nodes in clusters are evaluated serially before continuing with other parallel parts of the EG. Multiple clusters may be evaluated at the same time. As with previous versions of Maya, you should avoid creating scenes with attribute-level cycles as this is unsupported and leads to unspecified behavior.

By default, the EM schedules node evaluation on available CPU resources. However, the EM also provides the ability to override evaluation for sub-sections of the EG, using custom evaluators that target computation to specific runtimes and/or hardware. One example of this is the GPU override, which uses your graphics card’s graphics processing unit (GPU) to accelerate deformations.

Supported Evaluation Modes

Starting in Maya 2016, 3 evaluation modes are supported:

Mode What does it do?
DG Uses the legacy Dependency Graph-based evaluation of your scene. This was the default evaluation mode prior to Maya 2016
Serial Evaluation Manager Serial mode. Uses the EG but limits scheduling to a single core. Serial mode is a troubleshooting mode to pinpoint the source of evaluation errors.
Parallel Evaluation Manager Parallel mode. Uses the EG and schedules evaluation across all available cores. This mode is the new Maya default since 2016.

When using either Serial or Parallel EM modes, you can also activate GPU Override to accelerate deformations on your GPU. You must be in Viewport 2.0 to use this feature (see GPU Override).

To switch between different modes, go to the Preferences window (Windows > Settings/Preferences > Preferences > Animation). You can also use the evaluationManager MEL/Python command; see documentation for supported options.

To see the evaluation options that apply to your scene, turn on the Heads Up Display Evaluation options (Display > Heads Up Display > Evaluation).

First Make it Right Then Make it Fast

Before discussing how to make your Maya scene fast using Parallel evaluation, it is important to ensure that evaluation in DG and EM modes generates the same results. If you see different results in the viewport during animation (as compared to previous versions of Maya), or tests reveal numerical errors, it is critical to understand the cause of these errors. Errors may be due to an incorrect EG, threading related problems, or other issues.

Below, we review Evaluation Graph Correctness and Thread Safety, two important concepts to understand errors.

Evaluation Graph Correctness

In the event that you see evaluation errors, first try to test your scene in Serial evaluation mode (see Supported Evaluation Modes). Serial evaluation mode uses the EM to build an EG of your scene, but limits evaluation to a single core to eliminate threading as the possible source of differences. Note that since Serial evaluation mode is provided for debugging, it has not been optimized for speed and scenes may run slower in Serial than in DG evaluation mode. This is expected.

If transitioning to Serial evaluation eliminates errors, this suggests that differences are most likely due to threading-related issues. However, if errors persist (even after transitioning to Serial evaluation) this suggests that the EG is incorrect for your scene. There are a few possible reasons for this:

Custom Plugins. If your scene uses custom plug-ins that rely on the MPxNode::setDependentsDirty function to manage attribute dirtying, this may be the source of problems. Plug-in authors sometimes use MPxNode::setDependentsDirty to avoid expensive calculations in MPxNode::compute by monitoring and/or altering depencies and storing computed results for later re-use.

Since the EM relies on dirty propagation to create the EG, any custom plug-in logic that alters dependencies may interfere with the construction of a correct EG. Furthermore, since the EM evaluation does not propagate dirty messages, any custom caching or computation in MPxNode::setDependentsDirty is not called while the EM is evaluating.

If you suspect that your evaluation errors are related to custom plug-ins, temporarily remove the associated nodes from your scene and validate that both DG and Serial evaluation modes generate the same result. Once you have made sure this is the case, you will need to revisit the plug-in logic. The API Extensions section covers Maya SDK changes that will help you adapt plug-ins to Parallel evaluation.

Another debugging option is to use scheduling type overrides to force custom nodes to be scheduled more conservatively. This approach can enable the usage of Parallel evaluation even if only some of the nodes are thread-safe. Scheduling types are described in more details in the Thread Safety section.

Errors in Autodesk Nodes. Although we have done our best to ensure that all out-of-the-box Autodesk Maya nodes correctly express dependencies, sometimes a scene uses nodes in an unexpected manner. If this is the case, we ask you make us aware of scenes where you encounter problems. We will do our best to address problems as quickly as possible.

Thread Safety

Prior to Maya 2016, evaluation was single-threaded and developers did not need to worry about making their code thread-safe. At each frame, they were guaranteed that evaluation would proceed serially and computation would finish for one node prior to moving onto another. This approach allowed for the caching of intermediate results in global memory and using external libraries without considering their ability to work correctly when called simultaneously from multiple threads.

These guarantees no longer apply. Developers working in recent versions of Maya must update plug-ins to ensure correct behavior during concurrent evaluation.

Two things to consider when updating plug-ins:

Here’s a concrete example for a simple node network consisting of 4 nodes:

In this graph, evaluation first calculates outputs for Node1 (i.e., Node1.A, Node1.B, Node1.C), followed by parallel evaluation of Nodes 2, 3, and 4 (that is, Read Node1.A to use in Node2, Read Node1.B to use in Node3, etc.).

Since we know that making legacy code thread-safe requires time, we have added new scheduling types to provide control over how the EM schedule nodes. Scheduling types provide a straightforward migration path, so you do not need to pass up performance improvements, just because a few nodes still need work.

There are 4 scheduling types:

Scheduling Type What are you telling the scheduler?
Parallel Asserts that the node and all third-party libraries used by the node are thread-safe. The scheduler may evaluate any instances of this node at the same time as instances of other nodes without restriction.
Serial Asserts it is safe to run this node with instances of other nodes. However, all nodes with this scheduling type should be executed sequentially within the same evaluation chain.
Globally Serial Asserts it is safe to run this node with instances of other node types but only a single instance of this node type should be run at a time. Use this type if the node relies on static state, which could lead to unpredictable results if multiple node instances are simultaneously evaluated. The same restriction may apply if third-party libraries store state.
Untrusted Asserts this node is not thread-safe and that no other nodes should be evaluated while an instance of this node is evaluated. Untrusted nodes are deferred as much as possible (i.e. until there is nothing left to evaluate that does not depend on them), which can introduce costly synchronization.

By default, nodes scheduled as Serial provide a middle ground between performance and stability/safety. In some cases, this is too permissive and nodes must be downgraded to GloballySerial or Untrusted. In other cases, some nodes can be promoted to Parallel. As you can imagine, the more parallelism supported by nodes in your graph, the higher level of concurrency you are likely to obtain.

Tip. When testing your plug-ins with parallel Maya, a simple strategy is to schedule nodes with the most restrictive scheduling type (i.e., Untrusted), and then validate that the evaluation produces correct results. Raise individual nodes to the next scheduling level, and repeat the experiment.

There are three ways to alter the scheduling level of your nodes:

Evaluation Toolkit. Use this tool to query or change the scheduling type of different node types.

C++/Python API methods. Use the OpenMaya API to override the MPxNode::schedulingType and specify the desired node scheduling type. This function should return one of the enumerated values specified by MPxNode::schedulingType. See the Maya MPxNode class reference for more details.

Mel/Python Commands. Use the evaluationManager command to change the scheduling type of nodes at runtime. Below, we illustrate how you can change the scheduling of scene transform nodes:

Scheduling Type Command
Parallel evaluationManager -nodeTypeParallel on "transform"
Serial evaluationManager -nodeTypeSerialize on "transform"
GloballySerial evaluationManager -nodeTypeGloballySerialize on "transform"
Untrusted evaluationManager -nodeTypeUntrusted on "transform"

The Evaluation Toolkit and Mel/Python Commands method to alter node scheduling level works using node type overrides. They add an override that applies to all nodes of a given type. Using C++/Python API methods and overriding the MPxNode::schedulingType function gives the flexibility to change the scheduling type for each node instance. For example, expression nodes are marked as globally serial if the expression outputs are a purely mathematical function of its inputs.

The expression engine is not thread-safe so only one expression can run at a time, but it can run in parallel with any other nodes. However, if the expression uses unsafe commands (expressions could use any command to access any part of the scene), the node is marked as untrusted because nothing can run while the expression is evaluated.

This changes the way scheduling types should be queried. Using the evaluationManager command with the above flags in query mode will return whether or not an override has been set on the node type, using either the Evaluation Toolkit or the Mel/Python commands.

The Evaluation Toolkit window lets you query both the override type on the node type (which cannot vary from one node of the same type to the other) or the actual scheduling type used for a node when building the scheduling graph (which can change from one node instance to the other).

Safe Mode

On rare occasions you may notice that Maya switches from Parallel to Serial evaluation during manipulation or playback. This is due to Safe Mode, which attempts to trap errors possibly leading to instabilities, such as crashes. If Maya detects that multiple threads are attempting to simultaneously access a single node instance, evaluation will be forced to Serial execution to prevent problems.

Tip. If Safe Mode forces your scene into Serial mode, the EM may not produce the expected incorrect results when manipulating. In such cases you can either disable the EM:

evaluationManager -mode "off";

or disable EM-accelerated manipulation:

evaluationManager -man 0;

While Safe Mode catches many problems, it cannot catch them all. Therefore, we have also developed a special Analysis Mode that performs a more thorough and costly check of your scene. Analysis mode is designed for riggers/TDs wishing to troubleshoot evaluation problems during rig creation. Avoid using Analysis Mode during animation since it will slow down your scene.

Evaluation Graph Invalidation

As previously described, the EG adds necessary node-level scheduling information to the DG. To make sure evaluation is correct, it’s critical the EG always be up-to-date, reflecting the state of the scene. The process of detecting that things have changed and rebuilding the EG is referred to as graph invalidation.

Different actions may invalidate the EG, including:

Other less obvious actions include:

Frequent graph invalidations may limit parallel evaluation performance gains, since Maya requires DG dirty propagation and evaluation to rebuild the EG. To avoid unwanted graph rebuilds, consider immediately adding 2 keys, with slightly different values, on rig attributes you expect to use frequently. You can also lock static channels to prevent creation of static animation curves during keying. We expect to continue tuning this area of Maya, with the goal of making the general case as interactive as possible.

Tip. You can use the controller command to identify objects that will be used animation sources in your scene. If the Include controllers in evaluation graph option is set (see Windows > Settings/Preferences > Preferences, then Settings > Animation), the objects marked as controllers will automatically be added to the evaluation graph even if they are not animated yet. This will allow Parallel evaluation for manipulation even if they have not been keyed yet.

Custom Evaluators

In this section, we describe mechanisms to perform targeted evaluation of node sub-graphs. This approach is used by Maya to accelerate deformations on the GPU and to catch evaluation errors for scenes with specific nodes. Maya 2017 also introduced new Open API extensions, allowing user-defined custom evaluators.

Tip. Use the evaluator command to query the available/active evaluators or modify currently active evaluators. Some evaluators support using the nodeType flag to filter out or include nodes of certain types. Query the info flag on the evaluator for more information on what it supports.

# Returns a list of all currently available evaluators. 
import maya.cmds as cmds
cmds.evaluator( query=True )
# Result: [u'invisibility',
u'pruneRoots'] # 

# Returns a list of all currently enabled evaluators.
cmds.evaluator( query=True, enable=True )
# Result: [u'invisibility',
u'pruneRoots'] # 

GPU Override

Maya contains a custom deformer evaluator that aims to accelerate deformations in Viewport 2.0 by targetting deformation to the GPU. GPUs are ideally suited to tackle problems such as mesh deformations that require the same operations on streams of vertex and normal data. We have included GPU implementations for several of the most commonly-used deformers in animated scenes: skinCluster, blendShape, cluster, tweak, groupParts, softMod, deltaMush, lattice, nonLinear and tension.

Unlike Maya’s previous deformer stack that performed deformations on the CPU and subsequently sent deformed geometry to the graphics card for rendering, the GPU override sends undeformed geometry to the graphics card, performs deformations in OpenCL and hands off the data to Viewport 2.0 for rendering without read-back overhead. We have observed substantial speed improvements from this approach in scenes with dense geometry.

Even if your scene uses only supported deformers, GPU override may not be enabled due to use of unsupported node features in your scene. For example, with the exception of softMod, there is no support for incomplete group components. Additional deformer-specific limitations are listed below:

Deformer Limitation(s)
skinCluster The following attribute values will be ignored:
- bindMethod
- bindPose
- bindVolume
- dropOff
- heatmapFalloff
- influenceColor
- lockWeights
- maintainMaxInfluences
- maxInfluences
- nurbsSamples
- paintTrans
- smoothness
- weightDistribution
blendShape The following attribute values will be ignored:
- baseOrigin
- icon
- normalizationId
- origin
- parallelBlender
- supportNegativeWeights
- targetOrigin
- topologyCheck
cluster n/a
tweak Only relative mode is supported. relativeTweak must be set to 1.
groupParts n/a
softMod Only volume falloff is supported when distance cache is disabled
Falloff must occur on all axes
Partial resolution must be disabled
deltaMush n/a
lattice n/a
nonLinear n/a
tension n/a

A few other reasons that can prevent GPU override from accelerating your scene:

You can also increase support for new custom/proprietary deformers using new API extensions (refer to Custom GPU Deformers for details).

If you have enabled GPU Override and the HUD reports Enabled (0 k), this indicates that no deformations are happening on the GPU. There could be a number of reasons for this, such as those mentioned above.

To troubleshoot factors limiting use of GPU override for your particular scene, use the deformerEvaluator command. Supported options include:

Command What does it do?
deformerEvaluator Prints the chain or a each selected node is not supported.
deformerEvaluator -chains Prints all active deformation chains.
deformerEvaluator -meshes Prints a chain for each mesh or a reason if it is not supported.

Dynamics Evaluator

Starting in Maya 2017, the dynamics evaluator fully supports parallel evaluation of scenes with Nucleus (nCloth, nHair, nParticles), Bullet, and Bifrost dynamics. Legacy dynamics nodes (e.g., particles, fluids) remain unsupported. If the dynamics evaluator finds unsupported node types in the EG, Maya will revert to DG-based evaluation. The dynamics evaluator also manages the tricky computation necessary for correct scene evaluation. This is one of the ways custom evaluators can be used to change Maya’s default evaluation behavior.

The dynamics evaluator supports a number of configuration flags to control its behavior.

Flag What does it do?
disablingNodes specifies the set of nodes that will force the dynamics evaluator to disable the EM. Valid value are: legacy2016, unsupported, and none.
handledNodes specifies the set of nodes that are going to be captured by the dynamics evaluator and scheduled in clusters that it will manage. Valid values are: dynamics and none.
action specifies how the dynamics evaluator will handle its nodes. Valid values are: none, evaluate, and freeze.

In Maya 2017, the default configuration corresponds to:

evaluator -name dynamics -c "disablingNodes=unsupported";
evaluator -name dynamics -c "handledNodes=dynamics";
evaluator -name dynamics -c "action=evaluate";

where unsupported (i.e., blacklisted) nodes are:

This configuration will disable evalution if any unsupported nodes are encountered and perform evaluation for the other handled nodes in the scene.

To revert to Maya 2016 / 2016 Extension 2 behavior, use the configuration:

evaluator -name dynamics -c "disablingNodes=legacy2016";
evaluator -name dynamics -c "handledNodes=none";
evaluator -name dynamics -c "action=none";

where unsupported (i.e., blacklisted) nodes are:

Tip. To get a list of nodes that will make the dynamics evaluator disable the EM in its present configuration, use the following command:

evaluator -name "dynamics" -valueName "disabledNodes" -query;

You can configure the dynamics evaluator to ignore unsupported nodes. If you want to try Parallel evaluation on a scene where it is disabled because of the presence of unsupported node types, use the following commands:

evaluator -name dynamics -c "disablingNodes=none";
evaluator -name dynamics -c "handledNodes=dynamics";
evaluator -name dynamics -c "action=evaluate";

Note: Using the dynamics evaluator on unsupported nodes may cause evaluation problems and/or application crashes; this is unsupported behavior. Proceed with caution.

Tip. If you want the dynamics evaluator to skip evaluation of all dynamics nodes in the scene, use the following commands:

evaluator -name dynamics -c "disablingNodes=unsupported";
evaluator -name dynamics -c "handledNodes=dynamics";
evaluator -name dynamics -c "action=freeze";

This can be useful to quickly disable dynamics when the simulation has a big impact on animation performance.

Dynamics simulation results are very sensitive to evaluation order, which may differ between DG and EM-based evaluation. Even for DG-based evaluation, evaluation order may depend on multiple factors. For example, in DG-mode when rendering simulation results to the viewport, the evaluation order may be different than when simulation are performed in ‘headless mode’. Though EM-based evaluation results are not guaranteed to be identical to DG-based, evaluation order is consistent; once the evaluation order is scheduled by the EM, it will remain consistent regardless of whether results are rendered or Maya is used in batch. This same principle applies to non-dynamics nodes that are order-dependent.

Reference Evaluator

When a reference is unloaded it leaves several nodes in the scene representing reference edits to preserve. Though these nodes may inherit animation from upstream nodes, they do not contribute to what is rendered and can be safely ignored during evaluation. The reference evaluator ensures all such nodes are skipped during evaluation.

Invisibility Evaluator

Toggling scene object visibility is a critical artist workflow used to reduce visual clutter and accelerate performance. To bring this workflow to parallel evaluation, Maya 2017 and above includes the invisibility evaluator, whose goal is to skip evaluation of any node that does not contribute to a visible object.

The invisibility evaluator will skip evaluation of DAG nodes meeting any of the below criteria:

As of Maya 2018 the invisibility evaluator supports the isolate select method of hiding objects. If there is only a single viewport and it has one or more objects isolated then all of the other, unrelated objects will be considered invisible by the evaluator.

Also in Maya 2018 is support for the animated attribute on expression nodes. When this attribute is set to 1 the expression node is not skipped by the invisibility evaluator, even if there are only invisible objects connected to it.

Note: The default value of the animated attribute is 1 so in an expression-heavy scene you may see a slowdown from Maya 2017 to Maya 2018. To restore performance run the script below to disable this attribute on all expression nodes. (It is only required when the expression has some sort of side-effect external to the connections, such as printing a message or checking a cache file size.)

for node in type='expression' ):
    cmds.setAttr( '{}.animated'.format(node), 0 )

Tip: The invisibility evaluator is off by default in Maya 2017. Use the Evaluation Toolkit or this:

cmds.evaluator(enable=True, name='invisibility')

to enable the evaluator.

The invisibility evaluator only considers static visibility; nodes with animated visibility will still be evaluated, even if nodes meet the above criteria. If nodes are in a cycle, all cycle nodes must be considered invisible for evaluation to be skipped. Lastly, if a node is instanced and has at least one visible path upward, then all upward paths will be evaluated.

Tip: The invisibility evaluator determines its definition of visible solely from the node’s visibility state; if your UI or plug-in code requires invisible nodes to evaluate, do not use the Invisibility Evaluator.

Frozen Evaluator

The frozen evaluator allows users to tag EG subsections as not needing evaluation. It enhances the frozen attribute by propagating the frozen state automatically to related nodes, according to the rules defined by the evaluator’s configuration. It should only be used by those comfortable with the concepts of connection and propagation in the DAG and Evaluation Graph. Many users may prefer the invisibility evaluator; it presents a simpler interface/workflow for most cases.

The Frozen Attribute

The frozen attribute has existed on nodes since Maya 2016. It can be used to control whether or not node is evaluated in Serial or Parallel EM evaluation modes. In principle, when the frozen attribute is set, the EM skips evaluation of that node. However, there are additional nuances that impact whether or not this is the case:

Warning: Since all the frozen attribute does is skip evaluation, nothing is done to preserve the current node data during file store; if you load a file with frozen attributes set, the nodes may not have the same data as when you stored them.


The evaluation manager will not evaluate any node that has its frozen attribute set to True, herein referred to as explicitly frozen nodes. An implicitly frozen node is one that is disabled as a result of the operation of the frozen evaluator, but whose frozen attribute is not set to True. When the frozen evaluator is enabled it will also prevent evaluation of related nodes according to the rules corresponding to the enabled options, in any combination.

The frozen evaluator operates in three phases. In phase one it gathers together all of the nodes flagged by the invisible and displayLayers options as being marked for freezing. In phase two it propagates the freezing state outwards through the evaluation graph according to the values of the downstream and upstream options.

Phase 1: Gathering The Nodes

The list of nodes for propagation is gathered as follows:

Phase 2: Propagating The Freezing

The list gathered by Phase 1 will all be implicitly frozen. In addition, the downstream and upstream options may implicitly freeze nodes related to them. For each of the nodes gathered so far, the evaluation graph will be traversed in both directions, implicitly freezing nodes encountered according to the following options:

Phase 3: Runtime Freezing

If a node has its frozen or visibility states animated the evaluator still has to schedule it. The runtime freezing can still assist at this point in preventing unnecessary evaluation. Normally any explicitly frozen node will have its evaluation skipped, with all other nodes evaluating normally. When the runtime option is enabled, after skipping the evaluation of an explicitly frozen node no further scheduling of downstream nodes will occur. As a result, if the downstream nodes have no other unfrozen inputs they will also be skipped.

Note: The runtime option does not really modify the evaluator operation, it modifies the scheduling of nodes for evaluation. You will not see nodes affected by this option in the evaluator information (e.g. the output from cmds.evaluator( query=True, clusters=True, name='frozen' ))

Setting Options

Options can be set for the frozen evaluator in one of two ways:

Legal KEY and VALUE values are below, and correspond to the options as described above:

runtime True/False False
invisible True/False False
displayLayers True/False False
downstream ‘off’/‘safe’/‘force’ ‘off’
upstream ‘off’/‘safe’/‘force’ ‘off’

Unlike most evaluators the frozen evaluator options are stored in user preferences and will persist between sessions.


Other Evaluators

In addition to evaluators described above, additional evaluators exist for specialized tasks:

Evaluator What does it do?
curveManager Prepopulates the evaluation graph with unanimated nodes to be ready to use parallel evaluation with interactive manipulation. Prototype, work in progress.
timeEditorCurveEvaluator Finds all paramCurves connected to time editor nodes and puts them into a cluster that will prevent them from evaluating at the current time, since the time editor will manage their evaluation.
ikSystem Automatically disables the EM when a multi-chain solver is present in the EG. For regular IK chains it will perform any lazy update prior to parallel execution.
disabling Automatically disables the EM if user-specified nodes are present in the EG. This evaluator is used for troubleshooting purposes. It allow Maya to keep working stably until issues with problem nodes can be addressed.
hik Handles the evaluation of HumanIK characters in an efficient way by recognizing HumanIK common connection patterns.
transformFlattening Consolidates deep transform hierarchies containing animated parents and static children, leading to faster evaluation. Consolidation takes a snapshot of the relative parent/child transformations, allowing concurrent evaluation of downstream nodes.
pruneRoots We found that scenes with several thousand paramCurves become bogged down because of scheduling overhead from resulting EG nodes and lose potential gains from increased parallelism. To handle this situation, special clusters are created to group paramCurves into a small number of evaluation tasks, thus reducing overhead.

Custom evaluator names are subject to change as we introduce new evaluators and expand these functionalities.

Evaluator Conflicts

Sometimes, multiple evaluators will want to “claim responsibility” for the same node(s). This can result in conflict, negatively impacting performance. To avoid these conflicts, each evaluator is associated with a priority upon registration and nodes are assigned to the evaluator with the highest priority. Internal evaluators has been ordered to prioritize correctness and stability over speed.

API Extensions

Several API extensions and tools have been added to help you make the most of the EM in your pipeline. This section reviews API extensions for Parallel Evaluation, Custom GPU Deformers, Custom Evaluator API, and Profiling Plug-ins.

Parallel Evaluation

If your plug-in plays by the DG rules, you probably will not need many changes to make the plug-in work in Parallel mode. Porting your plug-in so it works in Parallel may be as simple as recompiling it against the latest version of OpenMaya!

If the EM generates different results than DG-based evaluation, make sure that your plug-in:

If your plug-in relies on custom dependency management, you need to use new API extensions to ensure correct results. As described earlier, the EG is built using the legacy dirty-propagation mechanism. Therefore, optimizations used to limit dirty propagation during DG evaluation, such as those found in MPxNode::setDependentsDirty, may introduce errors in the EG. Use MEvaluationManager::graphConstructionActive() to detect if this is occurring.

There are new virtual methods you will want to consider implementing:

Other recommended best practices include:

Custom GPU Deformers

To make GPU Override work on scenes containing custom deformers, Maya provides new API classes that allow the creation of fast OpenCL deformer back-ends.

Though you will still need to have a CPU implementation for the times when it is not possible to target deformations on the GPU (see GPU Override), you can augment this with an alternate deformer implementation inheriting from MPxGPUDeformer. This applies to your own nodes as well as to standard Maya nodes.

The GPU implementation will need to:

When you have done this, do not forget to load your plug-in at startup. Two working devkit examples (offsetNode and identityNode) have been provided to get you started.

Tip. To get a sense for the maximum speed increase you can expect by providing a GPU backend for a specific deformer, tell Maya to treat specific nodes as passthrough. Here’s an example applied to polySoftEdge:

       -name polySoftEdge
       -inputAttribute inputPolymesh 
       -outputAttribute output

Although results will be incorrect, this test can confirm if it is worth investing time implementing an OpenCL version of your node.

Custom Evaluator API

API classes and methods introduced in Maya 2017 let you define custom evaluators that allow control over how the Maya scene is computed.

To create a custom evaluator, you must define a plug-in that extends the MPxCustomEvaluator class. We describe the key class methods to override, below.

The Basics

Before you can use the new evaluators, they must be registered:

MStatus registerEvaluator(
    // name of the evaluator
    const char *     evaluatorName,  

    // evaluator priority. Higher priority evaluators get 'first-dibs'
    unsigned int     uniquePriority,

    // function pointer to method returning a new evaluator instance 
    MCreatorFunction creatorFunction

and deregistered:

MStatus deregisterEvaluator(
    // name of the evaluator
    const char* evaluatorName 

using MFnPlugin methods. These functions should be used during plug-in initialization:

MStatus initializePlugin( MObject obj )
    MFnPlugin plugin( obj, PLUGIN_COMPANY, "3.0", "Any");
    MStatus status = plugin.registerEvaluator(
    if (!status) 
    return status;

and uninitialization:

MStatus uninitializePlugin( MObject obj )
    MFnPlugin plugin( obj );
    MStatus status = plugin.deregisterEvaluator( "SimpleEvaluator" );
    if (!status)
    return status;

as illustrated above.

Once the plug-in has been loaded, you can to use Python or MEL commands to enable:

import maya.cmds as cmds
cmds.evaluator(enable=True, name='SimpleEvaluator')

# Result: False #


cmds.evaluator(enable=False, name='SimpleEvaluator')

# Result: True # 

and query information about evaluators:

print cmds.evaluator(query=True)

[u'invisibility', ... u'SimpleEvaluator']

NOTE: The evaluator command returns the previous state of the evaluator (as described in the documenation). This command fails if the evaluator cannot be enabled.

To view the priorities of all loaded evaluators, use the priority flag on the evaluator command:

for evaluatorName in cmds.evaluator():
    print "%-25s : %d" % (
        cmds.evaluator(name=evaluatorName, query=True, priority=True))

invisibility              : 1003000
frozen                    : 1002000
curveManager              : 1001000
timeEditorCurveEvaluator  : 104000
dynamics                  : 103000
ikSystem                  : 102000
disabling                 : 100000
hik                       : 7000
reference                 : 6000
deformer                  : 5000
transformFlattening       : 3000
pruneRoots                : 1000
SimpleEvaluator           : 40

API Reference

This section provides more detail on different MPxCustomEvaluator API methods.

Claiming clusters

During EG partitioning, each evaluator gets to claim evaluation nodes, using the:

bool MPxCustomEvaluator::markIfSupported(const MEvaluationNode* node)

method. You can safely cause evaluation in this call, but doing so increases partitioning and evaluation time. The developer can decide whether evaluation is required (call .inputValue / .inputArrayValue), or whether the previously-evaluated datablock values can be re-used (call .outputValue / .outputArrayValue). If multiple evaluators mark a specific node, which evaluator is assigned a node at run-time is determined by priority. For example, if you have two evaluators, A and B, mark node C of interest, if evaluator A has priority 100, and evaluator B has priority 10, during graph partitioning, evaluator A will get the opportunity to grab node C before evaluator B. Evaluators should not try to grab a node already grabbed by a higher-priority evaluator.


To determine if an evaluator can evaluate clusters in Parallel, use:

MCustomEvaluatorClusterNode::SchedulingType schedulingType(
    // a disjoint set of nodes on a custom evaluator layer
    const MCustomEvaluatorClusterNode * cluster 


SchedulingType Details
kParallel any number of nodes of the same type can run in parallel
kSerial all nodes of this type should be chained and executed sequentially
kGloballySerial only one node of this type can be run at a time
kUntrusted nothing else can execute with this node since we cannot predict what will happen

During EG scheduling:

bool MPxCustomEvaluator::clusterInitialize(
    const MCustomEvaluatorClusterNode* cluster // evaluation cluster node

can be used to perform the required cluster preparation. The pointer to the cluster remains valid until graph invalidation, such as when the scene topology changes.

Before the cluster is deleted,

void MPxCustomEvaluator::clusterTerminate(
    const MCustomEvaluatorClusterNode* cluster // the cluster to terminate

is called to allow needed cleanup, for example, releasing evaluator-specific resources. It is up to the custom evaluator to decide if it wants to clear its internal representation.


There are 3 main methods used during execution.

Prior to graph execution, the EM calls:

void MPxCustomEvaluator::preEvaluate(
    const MEvaluationGraph* graph // the graph about to be evaluated

during execution, the EM calls:

void MPxCustomEvaluator::clusterEvaluate(
    const MCustomEvaluatorClusterNode* cluster // the cluster to be evaluated

You will only receive clusters that belong to this evaluator. This call always happens after clusterInitialize and never after clusterTerminate. Finally,

void MPxCustomEvaluator::postEvaluate(
    const MEvaluationGraph* graph // the graph that was evaluated

is called just after a graph evaluation is finished.

SimpleEvaluator API Example

Now that we have reviewed relevant API methods, the following is an example that limits evaluation by caching previous results. simpleEvaluator assumes the existence of scene nodes that tag controller nodes with animation and works as follows:

In clusterInitialize, we build a list of translation and rotation attribute plugs.

// Build a list of plugs by scanning the scene for controller nodes.
// This gets called during scheduling.
bool simpleEvaluator::clusterInitialize(const MCustomEvaluatorClusterNode* cluster)
    if (fControllerPlugs.length() == 0)
    return true;

// Scan the scene for any controller nodes, populating the plug list.
// Called during the scheduling phase 
void simpleEvaluator::buildPlugListWithControllerTag()
    MStatus stat;
    MItDependencyNodes dgIter(MFn::kControllerTag, &stat);
    if (stat != MS::kSuccess)

    const char* values[] = {

    for (; !dgIter.isDone(); 
        MFnDependencyNode controllerTagNode(dgIter.thisNode(), &stat);
        if (stat != MS::kSuccess)

        MPlug currControllerTagPlug = 
            controllerTagNode.findPlug("controllerObject", &stat);
        if (stat != MS::kSuccess)

        // found controller tag node, now get its source controller
        MPlugArray source;
        bool retval = currControllerTagPlug.connectedTo(
            true /* asDst */, 
            false /* asSrc */, 
        if ((retval == false) || (stat != MS::kSuccess))

        // there should only be one source with the controller tag node
        // as destination
        MObject controllerNode = source[0].node(&stat);
        if (stat != MS::kSuccess)

        MFnDependencyNode currControllerNode(controllerNode, &stat);
        if (stat != MS::kSuccess)

        for (unsigned int j = 0; j < 6; j++)
            MPlug currPlug = currControllerNode.findPlug(values[j], &stat);
            if (stat == MS::kSuccess)
                    << "NO PLUG: " 
                    << "." 
                    << values[j] 
                    << std::endl;

Later, during preEvaluate, which is called per-frame, a hash value is calculated based on the plug values of the current frame.

void simpleEvaluator::preEvaluate(const MEvaluationGraph* graph)

void simpleEvaluator::buildHashValue()
    unsigned int length = fControllerPlugs.length();
    MStatus stat = MS::kSuccess;

    for (unsigned int i = 0; i < length; i++)
        float value = 0;
        stat = fControllerPlugs[i].getValue(value);

        if (stat == MS::kSuccess)
            boost::hash_combine(fCurrentHashValue, value);
                << "NO VALUE: " 
                << fControllerPlugs[i].name().asChar() 
                << std::endl;

This value is compared with the previous frame’s hash in clusterEvaluate. If the hash is different, the evaluation proceeds, otherwise we do nothing.

void simpleEvaluator::clusterEvaluate(const MCustomEvaluatorClusterNode* cluster)
    if (fOldHashValue != fCurrentHashValue)

To make sure the hash value is up-to-date, the hash value is stored in postEvaluate.

void simpleEvaluator::postEvaluate(const MEvaluationGraph* graph)
    fOldHashValue = fCurrentHashValue;
    fCurrentHashValue = 0;

Finally, when the graph topology becomes invalid, we call clusterTerminate to clear the cached list of plugs.

void simpleEvaluator::clusterTerminate(const MCustomEvaluatorClusterNode* cluster)
    if (fControllerPlugs.length() > 0)

Since simpleEvaluator claims control over the entire graph, markIfSupported returns true for all nodes. Additionally, nothing special is done to alter the cluster’s scheduling behavior.

bool simpleEvaluator::markIfSupported(const MEvaluationNode* node)
    return true;

simpleEvaluator::schedulingType(const MCustomEvaluatorClusterNode* cluster)
    return cluster->schedulingType();

See the provided simpleEvaluator devkit example for more details and complete source code.

Profiling Plug-ins

To visualize how long custom plug-ins are taking in the new profiling tools (see Profiling Your Scene) you will need to instrument your code. Maya provides C++, Python, and Mel interface for you to do this. Refer to the Profiling using MEL or Python or the API technical docs for more details.

Profiling Your Scene

In the past, it could be challenging to understand where Maya was spending time. To remove the guess work out of performance diagnosis, Maya includes a new integrated profiler that lets you see exactly how long different tasks are taking.

You can open the Profiler by selecting:

Once the Profiler window is visible:

  1. Load your scene and start playback
  2. Click Start in the Profiler to record information in the pre-allocated record buffer.
  3. Wait until the record buffer becomes full or click Stop in the Profiler to stop recording. The Profiler shows a graph demonstrating the processing time for your animation.
  4. Try recording the scene in DG, Serial, Parallel, and GPU Override modes.

Tip. By default the profiler allocates a 20MB buffer to store results. The record buffer can be expanded via the UI or using the profiler -b value; command, where value is the desired size in MB. This may be needed for more complex scenes.

The Profiler includes information for all instrumented code, including playback, manipulation, authoring tasks, and UI/Qt events. When profiling your scene, make sure to capture several frames of data to ensure gathered results are representative of scene bottlenecks.

The Profiler supports several views depending on the task you wish to perform. The default Category View, shown below, classifies events by type (e.g., dirty, VP1, VP2, Evaluation, etc). The Thread and CPU views show how function chains are subdivided amongst available compute resources. Currently the Profiler does not support visualization of GPU-based activity.

Now that you have a general sense of what the Profiler tool does, let’s discuss key phases involved in computing results for your scene and how these are displayed. By understanding why scenes are slow, you can target scene optimizations.

Every time Maya updates a frame, it must compute and draw the elements in your scene. Hence, computation can be split into one of two main categories:

  1. Evaluation (i.e., doing the math that determines the most up-to-date values for scene elements)
  2. Rendering (i.e., doing the work that draws your scene in the viewport).

When the main bottleneck in your scene is evaluation, we say the scene is evaluation-bound. When the main bottleneck in your scene is rendering, we say the scene is render-bound.

Evaluation-Bound Performance

There are several different problems that may lead to evaluation-bound performance.

Lock Contention. When many threads try to access a shared resource you may experience Lock Contention, due to lock management overhead. One clue that this may be happening is that evaluation takes roughly the same duration regardless of which evaluation mode you use. This occurs since threads cannot proceed until other threads are finished using the shared resource.

Here the Profiler shows many separate identical tasks that start at nearly the same time on different threads, each finishing at different times. This type of profile offers a clue that there might be some shared resource that many threads need to access simultaneously.

Below is another image showing a similar problem.

In this case, since several threads were executing Python code, they all had to wait for the Global Interpreter Lock (GIL) to become available. Bottlenecks and performance loses caused by contention issues may be more noticeable when there is a high concurrency level, such as when your computer has many cores.

If you encounter contention issues, try to fix the code in question. For the above example, changing node scheduling converted the above profile to the following one, providing a nice performance gain. For this reason, Python plug-ins are scheduled as Globally Serial by default. As a result, they will be scheduled one after the other and will not block multiple threads waiting for the GIL to become available.

Clusters. As mentioned earlier, if the EG contains node-level circular dependencies, those nodes will be grouped into a cluster which represents a single unit of work to be scheduled serially. Although multiple clusters may be evaluated at the same time, large clusters limit the amount of work that can be performed simultaneously. Clusters can be identified in the Profiler as bars with the opaqueTaskEvaluation label, shown below.

If your scene contains clusters, analyze your rig’s structure to understand why circularities exist. Ideally, you should strive to remove coupling between parts of your rig, so rig sections (e.g., head, body, etc.) can be evaluated independently.

Tip. When troubleshooting scene performance issues, you can temporarily disable costly nodes using the per-node frozen attribute. This removes specific nodes from the EG. Although the result you see will change, it is a simple way to check that you have found the bottleneck for your scene.

Render-Bound Performance

The following is an illustration of a sample result from the Maya Profiler, zoomed to a single frame measured from a large scene with many animated meshes. Because of the number of objects, different materials, and the amount of geometry, this scene is very costly to render.

The attached profile has four main areas:

In this scene, a substantial number of meshes are being evaluated with GPU Override and some profiler blocks appear differently from what they would otherwise.

Evaluation. Area A depicts the time spent computing the state of the Maya scene. In this case, the scene is moderately well-parallelized. The blocks in shades of orange and green represent the software evaluation of DG nodes. The blocks in yellow are the tasks that initiate mesh evaluation via GPU Override. Mesh evaluation on the GPU starts with these yellow blocks and continues concurrently with the other work on the CPU.

An example of a parallel bottleneck in the scene evaluation appears in the gap in the center of the evaluation section. The large group of GPU Override blocks on the right depend on a single portion of the scene and must wait until that is complete.

Area A2 (above area A), depicts blue task blocks that show the work that VP2 does in parallel to the scene evaluation. In this scene, most of the mesh work is handled by GPU Override so it is mostly empty. When evaluating software meshes, this section shows the preparation of geometry buffers for rendering.

GPUOverridePostEval. Area B is where GPU Override finalizes some of its work. The amount of time spent in this block varies with different GPU and driver combinations. At some point there will be a wait for the GPU to complete its evaluation if it is heavily loaded. This time may appear here or it may show as additional time spent in the Vp2BuildRenderLists section.

Vp2BuildRenderList. Area C. Once the scene has been evaluated, VP2 builds the list of objects to render. Time in this section is typically proportional to the number of objects in the scene.

Vp2PrepareToUpdate. Area C2, very small in this profile. VP2 maintains an internal copy of the world and uses it to determine what to draw in the viewport. When it is time to render the scene, we must ensure that the objects in the VP2 database have been modified to reflect changes in the Maya scene. For example, objects may have become visible or hidden, their position or their topology may have changed, and so on. This is done by VP2 Vp2PrepareToUpdate.

Vp2PrepareToUpdate is slow when there are shape topology, material, or object visibility changes. In this example, Vp2PrepareToUpdate is almost invisible since the scene objects require little extra processing.

Vp2ParallelEvaluationTask is another profiler block that can appear in this area. If time is spent here, then some object evaluation has been deferred from the main evaluation section of the Evaluation Manager (area A) to be evaluated later. Evaluation in this section uses traditional DG evaluation.

Common cases for which Vp2BuildRenderLists or Vp2PrepareToUpdate can be slow during Parallel Evaluation are:

Vp2Draw3dBeautyPass. Area D. Once all data has been prepared, it is time to render the scene. This is where the actual OpenGL or DirectX rendering occurs. This area is broken into subsections depending on viewport effects such as depth peeling, transparency mode, and screen space anti-aliasing.

Vp2Draw3dBeautyPass can be slow if your scene:

Other Considerations. Although the key phases described above apply to all scenes, your scene may have different performance characteristics.

For static scenes with limited animation, or for non-deforming animated objects, consolidation is used to improve performance. Consolidation groups objects that share the same material. This reduces time spent in both Vp2BuildRenderLists and Vp2Draw3dBeatyPass, since there are fewer objects to render.

Saving and Restoring Profiles

Profile data can be saved at any time for later analysis using the Edit -> Save Recording... or Edit -> Save Recording of Selected Events... menu items in the Profiler window. Everything is saved as plain string data (see the appendix describing the profiler file format for a description of how it is stored) so that you can load profile data from any scene using the Edit -> Load Recording... menu item without loading the scene that was profiled.

Troubleshooting Your Scene

Analysis Mode

The purpose of Analysis Mode is to perform more rigorous inspection of your scene to catch evaluation errors. Since Analysis Mode introduces overhead to your scene, only use this during debugging activities; animators should not enable Analysis Mode during their day-to-day work. Note that Analysis Mode is not thread-safe, so it is limited to Serial; you cannot use analysis mode while in Parallel evaluation.

The key function of Analysis Mode is to:

Tip. To activate Analysis Mode, use the dbtrace -k evalMgrGraphValid; MEL command.

Once active, error detection occurs after each evaluation. Missing dependencies are saved to a file in your machine’s temporary folder (e.g., %TEMP%\_MayaEvaluationGraphValidation.txt on Windows). The temporary directory on your platform can be determined using the internalVar -utd; MEL command.

To disable Analysis Mode, type: dbtrace -k evalMgrGraphValid -off;

Let’s assume that your scene contains the following three nodes. Because of the dependencies, the evaluation manager must compute the state of nodes B and C prior to calculating the state of A.

Now let’s assume Analysis Mode returns the following report:

Detected missing dependencies on frame 56
     A.output <-x- B
     A.output <-x- C [cluster]
Detected missing dependencies on frame 57
    A.output <-x- B
    A.output <-x- C [cluster]

The <-x- symbol indicates the direction of the missing dependency. The [cluster] term indicates that the node is inside of a cycle cluster, which means that any nodes from the cycles could be responsible for attribute access outside of evaluation order

In the above example, B accesses the output attribute of A, which is incorrect. These types of dependency do not appear in the Evaluation Graph and could cause a crash when running an evaluation in Parallel mode.

There are multiple reasons that missing dependencies occur, and how you handle them depends on the cause of the problem. If Analysis Mode discovers errors in your scene from bad dependencies due to:

Graph Execution Order

There are two primary methods of displaying the graph execution order.

The simplest is to use the ‘compute’ trace object to acquire a recording of the computation order. This can only be used in Serial mode, as explained earlier. The goal of compute trace is to compare DG and EM evaluation results and discover any evaluation differences related to a different ordering or missing execution between these two modes.

Keep in mind that there will be many differences between runs since the EM executes the graph from the roots forward, whereas the DG uses values from the leaves. For example in the simple graph shown earlier, the EM guarantees that B and C will be evaluated before A, but provides no information about the relative ordering of B and C. However in the DG, A pulls on the inputs from B and C in a consistent order dictated by the implementation of node A. The EM could show either "B, C, A" or "C, B, A" as their evaluation order and although both might be valid, the user must decide if they are equivalent or not. This ordering of information can be even more useful when debugging issues in cycle computation since in both modes a pull evaluation occurs, which will make the ordering more consistent.

The Evaluation Toolkit

A set of debugging tools used to be shipped as a special shelf in Maya Bonus Tools, but they are now built-in within Maya. The Evaluation Toolkit provides features to query and analyze your scene and to activate / deactivate various modes. See the accompanying Evaluation Toolkit documentation for a complete list of all helper features.

Known Limitations

This section lists known limitations for the new evaluation system.


Profiler File Format

The profiler stores its recording data in human-readable strings. The format is versioned so that older format files can still be read into newer versions of Maya (though not necessarily vice-versa).

This is a description of the version 1 format, present in versions of Maya up to and including 2018.

First, a content example:

1     #File Version, # of events, # of CPUs
2     2\t12345\t8
3     Main\tDirty
4     #Comment mapping---------
5*    @27 = MainMayaEvaluation
6     #End comment mapping---------
7     #Event time, Comment, Extra comment, Category id, Duration, \
          Thread Duration, Thread id, Cpu id, Color id
8*    1234567\t@12\t@0\t2\t12345\t11123\t36\t1\t14
9     #Begin Event Tag Mapping---------
10    #Event ID, Event Tag
11*   123\tTaggy McTagface
12    #End Event Tag Mapping---------
13    #Begin Event Tag Color Mapping---------
14    #Tag Label, Tag Color
15*   Taggy\tMcTagface\t200\t200\t13
16    #End Event Tag Color Mapping---------

The following table describes the file format structure by referring to the previous content:

Line(s) Description


A header line with general file information names


A tab-separated line containing the header information


A tab-separated line containing the list of categories used by the events (category ID is the index of the category in the list)


A header indicating the start of comment mapping (a mapping from an ID to the string it represents)


Zero or more lines lines mapping a number onto a string in the form @LINE = STRING. The IDs do not correspond to anything outside of the file.


A footer indicating the end of comment mapping


A header indicating the start of event information. The names are the titles of the event columns.

  • Event time is the absolute time, in ticks, the event started
  • Duration is the total amount of time, in ticks, for the entire event
  • Thread duration is the total amount of time, in ticks, the event took inside the thread
  • Comment and Extra comment use an ID from the comment mapping above
  • Category id is the index of the event’s category from the list at line 3
  • Cpu id and Thread id are the ones in which the event took place. Actual values are arbitrary; only meant to distinguish unique CPUs and Threads
  • Color id is an index into the color mapping internal to the app (colors at the time of creation are not stored in the file).


Zero or more tab-separated lines mapping to all of the events that were stored in the file


A header indicating the start of the event tag maps


A title line showing what values are in the event tag map columns


Zero or more tab-separated lines attaching an event tag, defined through the profiler tool, to a specific event ID. The event ID will correspond to the ID given to it in the comment mapping section.


A footer indicating the end of the event tag maps


A header indicating the start of the event tag color maps


A title line showing what values are in the event tag color map columns


Zero or more tab-separated lines mapping a tag label defined above to an R,G,B color


A header indicating the end of the event tag color maps


Sample version 2 file on 4 CPUs containing a single event of type “ETName”, description “ETDescription”, in category “ETCategory” with description “Category description”, using color 7, of duration 100 ticks, starting at tick 999, on a single thread with ID 22, tagged with “TagMe” which has color red (255 0 0)

#File Version, # of events, # of CPUs
2   1   4
Category description
#Comment mapping---------
@0 = ETName
#End comment mapping---------
999 @0  @0  1   100 100 22  1   7
#Begin comment description mapping---------
@1 = ETDescription
#End comment description mapping---------
#Begin Event Tag Mapping---------
#Event ID, Event Tag
1   TagMe
#End Event Tag Mapping---------
#Begin Event Tag Color Mapping---------
#Tag Label, Tag Color
TagMe   255 0 0
#End Event Tag Color Mapping---------

Debugging Commands

Several commands can be used to help display information about your scene to help in debugging or optimizations. This is a summary of some of the more common ones, and represents only the available runtime information. Consult the command documentation in Maya’s online technical documentation for more information about each command.


Maintains embedded code location counters for higher-level debugging of scene operation. Generally, this uses specialized code that is only available in custom builds.

Synopsis: dbcount [flags]
   -e -enabled      on|off
   -f -file         String
   -k -keyword      String
   -l -list        
  -md -maxdepth     UnsignedInt
   -q -quick       
   -r -reset       
   -s -spreadsheet 

Command Type: Command


Monitors messaging that adds and removes DAG and DG nodes.

Synopsis: dbmessage [flags]
   -f -file     String
   -l -list    
   -m -monitor  on|off
   -t -type     String

Command Type: Command


Turns on conditional code, typically to print out status information or to take different code paths when enabled.

To find available trace objects use dbtrace –q to list currently-enabled traces, and dbtrace –q –off to list currently-disabled traces.

See below for information on specific keywords.

Note: Work is currently in progress to make these trace objects more flexible. It is a current design constraint that sometimes they are visible in a release, even though they only function internally, and some cannot be used when using Parallel evaluation.

Synopsis: dbtrace [flags]
   -q -query
   -f -filter   String
   -i –info
   -k -keyword  String (multi-use)
              (Query Arg Optional)
   -m -mark    
   -o -output   String
 -off -        
   -t -title    String
  -tm -timed    on|off
   -v -verbose 

Command Type: Command
Keyword Description Contents (Default Output File)
cipEM Shows what Customer Improvement Program data is being collected. Generic usage information. No longer being used (n/a)
cmdTracking Enables the tracking of counts of commands. Use the dbpeek ‘cmdTracking’ operation to view the results. No output, but enables tracking of the counts for all commands being executed. (For example, you can turn it on during file load to get a count of the number of createNode calls, including those in referenced files, a task that is difficult to do manually) (n/a)
compute High level trace of the compute path Nested output showing compute methods being called. Typically in EM mode you should see nesting only in cycles. DG mode will show the full set of nodes triggered by a single evaluation request (_Trace_Compute.txt)
dbCache Data block manipulation Details of the creation and manipulation of datablock information (_Trace_DataBlockCache.txt)
deformerEvaluator Statistics for the deformer evaluator setup Shows statistics on what the deformer evaluator was able to ingest, once enabled (cerr)
evalMgrGraphCreation Internal use only (n/a)
evalMgrGraphSched Internal use only (n/a)
evalMgrGraphValid Evaluation manager execution graph validation errors and warnings Nodes that were evaluated while in EMS mode using the pull (DG) model. This indicates missing dependencies in the evaluation graph, possibly caused by custom dirty propagation (_MayaEvaluationGraphValidation.txt)
evalMgrSched Internal use only (n/a)
idleBuild Operation of the idle build mechanism for the evaluation graph When the idle build is active, this appears when the idle build is triggered and executed (_Trac_EGBuild.txt)
nodeTracking Enables tracking of counts of created nodes. Use the dbpeek ‘nodeTracking’ operation to view results. (n/a)
peekData Shows progress of the dbpeek -op data operation Dumps data collected by the dbpeek operation, and how (_Trace_DbPeekData.txt)
peekMesh Shows progress of the dbpeek -op data operation Dumps data collected by the dbpeek operation, and with what flags (_Trace_DbPeekMesh.txt)


Historical debugging command; not robust or documented. Deprecated: Use the newer dbpeek command.

No help is provided for this command.


Forces dirty/clean states onto specified plugs and everything downstream from them. Meant to be a safety net for restoring proper states to your scene when something has gone wrong.

You should not need to use this command, but it will continue to exist as a “reset button”, just in case.

Synopsis: dgdirty [flags] [String...]
   -q -query
   -a -allPlugs    
   -c -clean       
   -i -implicit    
   -l -list         String
   -p -propagation 
  -st -showTiming  
   -v -verbose     

Command Type: Command


Forces the node to compute certain plugs. Like dgdirty, this command is meant to be a safety net if computation has not occurred in the proper order. Similar in function to the getAttr command, but since it returns no results, it can handle all attribute types, not only those supported by getAttr.

Synopsis: dgeval [flags] String...
 -src -        
   -v -verbose 

Command Type: Command


Dumps information about the current state of the graph. Be aware that when plug dirty states are reported, they represent the connection associated with the plug. In fan-out or in-out connections there will be more than one dirty state associated with the connection attached to the plug. This means it is legal to see A->B as dirty but B->A as clean if A has multiple connections. Being Deprecated: Use the newer dbpeek command.

Synopsis: dgInfo [flags] [String...]
 -all -allNodes     
   -c -connections  
   -d -dirty         on|off
   -n -nodes        
  -nd -nonDeletable 
  -nt -type          String
  -of -outputFile    String
   -p -propagation   on|off
   -s -short        
 -sub -subgraph     
  -sz -size         

Command Type: Command


Checks on the reason a file requests saving when no changes have been made.

Synopsis: dgmodified

No Flags.


This command is called out intentionally, as it combines multiple operations into a single command by use of various operations.

It runs one of several operations that provide a view into the data internals in the scene. This is the most useful and flexible of the debugging commands, and new variations of it are often being introduced. Use dbpeek -q -op to show a list of currently available operations and dbpeek -op X -q to show detailed help for operation X.

See below for information on specific keywords.

Note: The syntax of the argument flag allows for both keyword argument=’key’ and keyword/value argument=’key=value’ forms.

Synopsis: dbpeek [flags] [String...]
   -q -query
   -a -argument         String (multi-use) (Query Arg Mandatory)
 -all -allObjects      
   -c -count            UnsignedInt
  -eg -evaluationGraph 
  -of -outputFile       String
  -op -operation        String (Query Arg Optional)

Command Type: Command

dbpeek -op attributes

Analyzes node or node-type attributes and dumps information about them based on what the selected operation type.

Various arguments to the operation change the content of the output. The essence remains the same; the attributes belong to the node or node type.

Argument Meaning
detail Adds all internal details from attributes being dumped, otherwise dumps only the names and structure. The details are output as object members of the attribute, including the children.
nodeType Dumps all attributes belonging to the selected node(s) types. If nothing is selected, it dumps the attributes for all available node types. This includes all node types up the hierarchy to the base node class.
noDynamic Skips dynamic attributes in all output.
noExtension Skips extension attributes in all output.
noStatic Skips static attributes in all output.
onlyPlugins Restricts any output to nodes and node types that originate from a plug-in.
type=affects Dumps attribute structure and affects relationships in the graphical .dot format.
type=detail Dumps attribute information in .json format. This is the default if no type is specified.
type=validate Validates flags and structure for consistency and validity.

If no nodes are selected, then this command prints the list of all attributes on all nodes. For example, if you had a node type called reversePoint with a vector input and a vector output.

type=detail would output this JSON data:

  "nodes" :
    "reversePoint" :
      "staticAttributes" : [
        { "pointInput" : [
        { "pointOutput" :
      "extensionAttributes" : []

type=affects would output this DOT data:

digraph G
    subgraph cluster_NODENAME
        label="Node NODENAME, Type NODETYPE";
        color=".7 .0 .0";
        ia [label="ia/inputAttribute",style="rounded",shape=ellipse];
        oa [label="oa/outputAttribute",style="rounded",shape=rectangle];
        ia -> oa;

and type=validate would output this JSON validation summary:

  "Attribute Validation" :
    "NODENAME" :
      "staticAttributes" :
          "Both input and output attributes in compound" :
            { "root" : "rootAttribute",
              "inputs" : ["inputChild"],
              "outputs" : ["outputChild"],

dbpeek -op cmdTracking

By default, when no detail argument is present it shows a list of all commands run since the last reset as well as a count of how many of each type were executed.

Outputs in command/count pair form, one per line, with a tab character separating them.

Argument Meaning
reset Set all of the command tracking statistics to zero

dbpeek -op connections

By default, when no type argument is present, shows a list of all connections in the DG.

Argument Meaning
summary Reduces the output to show only the connection counts on the nodes. It separates by single and multi but no further information is added. Useful for getting basic usage information.
verbose Shows extra information about every connection, including dirty/propagation states, plug ownership, and type connectivity of the connection. Connections can be single or multi, and be connected either to each other or to plugs.

dbpeek -op data

Dumps the current contents of a node’s plug data in a standard format. By default the output is in CSV format consisting of 5 columns: NODE PLUG DATA_TYPE CLEAN_STATE DATA_AS_TEXT

Example for a simple integer attribute with a dirty value of 5: MyNode MyPlug Int32 0 5

Argument Meaning
eval Evaluates plugs first to guarantee that they are clean. Note: Some plugs are always dirty so there may still be plugs that show a dirty value.
full Includes plugs with default values in the output.
json Uses JSON format for the output. The general form is { "NODE" : { "PLUG" : { "TYPE", "CLEAN", "VALUE" } } }. For example, a simple numeric attribute with a dirty value of 5 { "MyNode" : { "MyPlug", "0", "5" } }
matrix Includes all plugs with a “matrix” data type in the output. This does not include generic data that may have a matrix value at runtime, only attributes that are exclusively matrix types.
number Includes all plugs with any numerical data type in the output. This does not include any generic data that may have numerical value at runtime, only attributes that are exclusively numeric types. It includes all types of numeric values, including linear, angular, time, and unitless values.
state Includes the current dirty state of the data in the output.
time=TIME Rather than evaluating at the normal context, evaluates at a context using the given time. This is somewhat equivalent to getAttr -t TIME.
vector Includes all plugs with a “vector” data type in the output. Does not include generic data that may have a vector value at runtime, only attributes that are exclusively double[3] types.

dbpeek -op context

Analyzes context evaluation to detect various errors violating the design.

Argument Meaning
isolationType=animatedAttributes Filters errors, reporting only those involving animated attributes
isolationType=animatedNodes Filters errors, reporting only those involving animated nodes
isolationType=staticAndAnimated Reports all errors
test=isolation During evaluation, detects when evaluation context is violated causing data to be read or written into a state that belongs to some other evaluation context
test=correctness Evaluates the scene in the background, comparing evaluation data stored for background and main context; compares traversing evaluation graph visiting nodes only if all upstream nodes generate equivalent data in both the background and the main context
time=TIME Takes a string value indicating the frame time at which evaluation should be performed.
verbose Adds extra information to output report. Each test will have its own verbose data. Isolation: Adds callstack information to the report for each detected error. Correctness: Adds attributes which compare failed to compare (due to missing logic)

Sample output for isolation tests:

    "context isolation": {
        "frame": 5.0,
        "type": "animatedNodes",
        "verbose": true,
        "errors": [
                "node": "ikHandle1",
                "type": "ikHandle",
                "attribute": "ikFkManipulation",
                "call stack": [
                    "METHOD Line NUMBER",
                    "METHOD Line NUMBER",
                    "METHOD Line NUMBER"
                "node": "shape",
                "type": "mesh",
                "attribute": "displaySmoothMesh",
                "call stack": [
                    "METHOD Line NUMBER",
                    "METHOD Line NUMBER",
                    "METHOD Line NUMBER"
        "time out": true

Sample output for correctness tests:

    "context correctness": {
        "frame": 14.0,
        "verbose": true,
        "errors": [
                "node": "IKSpineCurveShape",
                "type": "nurbsCurve",
                "attributes": [
        "failed to compare": [
        "time out": true

dbpeek -op edits

Shows a list of all nodes for which tracking is currently enabled. The “track” flag is mandatory.

Argument Meaning
track Shows a list of all nodes for which tracking is currently enabled.

dbpeek -op evalMgr

Outputs the current state of all of the custom evaluators used by the Evaluation Manager.

Argument Meaning
custom Outputs the custom evaluators registered with the evaluation manager.
global Adds output that is independent of scene contents, for example, node types enabled for the custom evaluators.
local Adds output that is specific to the scene contents, for example, nodes supported by a custom evaluator.

dbpeek -op graph

Gets a list of nodes or connections from either the dependency graph or the underlying evaluation graph.

Argument Meaning
connections Dumps the list of all connections in the chosen graph. The sorting order is alphabetical by destination plug name.
dot Dumps the graph information in .dot format for parsing and display by an external application such as graphViz.
evaluationGraph Gets the structure information from the evaluation graph, otherwise uses the raw dependency graph. The dbpeek command flag “evaluationGraph” does the same thing.
graph Dumps the graph state and contents, not including what is dumped by any of the other flags.
nodes Dumps the list of all nodes in the chosen type of graph, in alphabetical order by full node name.
plugs For the evaluation graph option, dumps the list of all plugs in its dirty plug list in the evaluation nodes. For the DG option, dumps the list of plugs currently in the plug trees.
scheduling Dumps the scheduling type used for all nodes in the type of graph in the form NODE = SCHEDULING_TYPE. If a node type is specified, the default scheduling type for nodes of that specific node type is returned in the same format.
verbose When dumping the scheduling graph in .dot format, adds all of the names of the nodes to the clusters. Otherwise, it is only a count of nodes in each cluster

dbpeek -op mesh

Dumps the current contents of the mesh to a standard format. There are two types of formatting and two levels of detail to present.

Argument Meaning
eval Evaluates mesh plugs first to guarantee they are clean. Otherwise the values currently present in the mesh shape are used as-is.
json Dumps data in JSON format instead of CSV.
verbose Puts full values for all of the data in the output. Otherwise, only a number count of each type is returned. See the flag descriptions for more information on which data can be requested and what is returned for each type.
vertex Includes vertex position or vertex count in the output. The short return is a count of vertices in the mesh. The verbose values are a list of vertex number and the {X,Y,Z} positions of the vertex, with W factored in, if appropriate.

For the default level of detail, the default CSV format output will look like this:


For example, a cube containing 32 vertices would have these lines:


The JSON equivalent format would look like this:

   "pCubeShape1" : {
       "outMesh" : "32"

If the full detail is requested, then the (abbreviated) output for CSV format will look like this:

pCubeShape1,outMesh[0],1,0.0 0.0 0.0
pCubeShape1,outMesh[1],1,0.0 0.5 0.0
pCubeShape1,outMesh[32],1,1.0 1.0 1.0

and like this for JSON format:

 "pCubeShape1" : {
    "outMesh" : {
      "clean" : 1,
      "0" : { ["0.0", "0.0", "0.0"] },
      "1" : { ["0.0", "0.5", "0.0"] }
     "32": { ["1.0", "1.0", "1.0"] }


dbpeek -op metadata

Shows node metadata. The default operation shows a list of all nodes containing metadata.

Argument Meaning
summary Shows a single line per node, with metadata indicating how many channels, streams, and values are present in the metadata.
verbose Shows a detailed list of all metadata on nodes, including a dump in the debug serialization format for each of the metadata streams.

dbpeek -op node

Show select debugging information on DG nodes. See also the “plug” and “connection” operations for display of information specific to those facets of a node. If no arguments are used then the ones marked as [default] will all be enabled, for convenience.

Argument Meaning
datablock [default] Shows the values in the datablock(s)
datablockMemory Shows raw datablock memory. This is independent of the other other datablock flags.
dynamicAttr Shows dynamic attributes.
evaluationGraph [default] Includes evaluation graph information on the node
extensionAttr Shows the extension attributes
node [default] Shows information specific to individual node types, such internal caches, flags, or special relationships it maintains. All other data shown is common to all node types
plug [default] Shows the nodes plug information
skipClean Does not include datablock values that are clean
skipDirty [default] Does not include the datablock values that are dirty
skipMulti Does not include the datablock values that are multi (array) attributes
staticAttr Shows the static attributes
verbose Shows much more detail where available. This will include things such as flags set on objects, full detail on heavy data, and any extra detail specific to a node type, such as caches.

dbpeek -op nodes

By default, when no detail argument is present, shows a list of all currently registered node types.

Argument Meaning
binary Also includes the IFF tag used to identify each node type in the “.mb” file format

dbpeek -op nodeTracking

By default, when no argument is present, shows a list of all nodes created since the last reset along with a count of how many of each type were created. Output is in the form of nodeType/count pairs, one per line, with a tab character separating them.

Argument Meaning
reset Erases all of the node tracking statistics.

dbpeek -op plugs

Shows information about all of the plugs in a scene. By default, when no argument is present, shows static plug footprint. A lot of this is only displayed in specially-instrumented builds, and generally only of use internally.

Argument Meaning
details Includes the full plug/node name information in the output. Otherwise only the total and summary counts are dumped.
group=stat Groups all output by statistic name
group=node Groups all output by node name
mode=footprint Reports size information for currently-existing networked plugs.
mode=usage Reports dynamic code path statistics, if they have been enabled in the current build
mode=reset When used in conjunction with “usage”, resets the statistics back to zero.
mode=state Gets unevaluated state information for boolean plugs. Only available on specially-built cuts.
nodeType=TYPE Restricts the operation to the node types specified in the argument. This includes inherited types, for example if the value is “transform”, then the operation also applies to “joint” nodes, as the node type “joint” inherits from the node type “transform”. See the node type documentation or the nodeType command for complete information on which node types inherit from each other.
stat=STAT If this argument has no STAT, then sorts by the name of the statistic. If this argument does have a STAT, for example, “stat=addToNet”, then only reports that statistic. Only available on specially-built cuts.




2016 Extension 2