Chapter 9, Pre-Compositing
| Using Pre-Compositing Templates | |
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Importing Maya 2008 Render Layers |
Chapter 9, Pre-Compositing |
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Working with Stereoscopic Compositions
The creation and update of pre-comp files always starts with the scene compositions, working its way down to the render layers and finally the render pass compositions.
The scene/layer/pass compositions are named accordingly: <scene anchor> <camera anchor> <layer anchor> <pass anchor>.
Warning: Renaming compositions will impair the update process.
All nodes, including output nodes, in each type of composition can be renamed, since node anchors are used to keep track of the topology during import.
Pre-comp import updates are completely non-destructive. When an update is needed on a composition of any type (render layer, render pass, or scene), modifications are applied to a new version of the composition (if you turned on the Backup Working Version option in the Pre-Compositing Import Options dialog box or project preferences), which could be a clone of the working version or a new version recreated from scratch.
Moreover, when an update is applied on a clone of the working version, none of the existing nodes in it are deleted (only new content is added) and existing connections are preserved.
Partial updates are also supported. That is, only some cameras or some render layers and passes could be modified during a pre-composition update.
A scene, render layer, or render pass composition is not updated if it doesn't need to be. You can re-export the entire contents of the scene and only the content that needs to be updated will be.Changing the path or the content of a pre-compositing template will not trigger an update as the Toxik application does not detect when the template has changed. In this case, you should use the Recreate Working Version update mode in the Pre-Compositing Import Options dialog box or project preferences.
Since Toxik does not support all frame rates, there may be cases where the time units in the 3D application, such as Maya, may correspond to an unsupported rate in Toxik. During import of the pre-comp file, Toxik finds and uses the closest supported rate. However, a warning is displayed which applies to all types of compositions (render layer, render pass, or scene).
The render pass image files are imported in a new footage composition. If the files are in OpenEXR format, the appropriate channels are selected.
The render pass files don't need to be on disk for them to be imported by Toxik in the correct image and pixel format and time range because all of this information can be queried by Toxik through the pre-comp file. Also, pre-multiplication with the proper background color is handled correctly.
If the render pass file names do not have extensions or if the extension does not correspond to an image file format that Toxik can import, a warning is issued, but the render pass composition is still created and its Import node holds the specified sequence path, however, it produces a red X frame.
The render pass footage can be anywhere on disk, organized in an arbitrary folder hierarchy. The files can be in any format that Toxik supports during import--see Supported Media Formats. If rendered to OpenEXR, the render passes can be stored in any file channel. The pre-compositing import is totally independent from the way images are organized on disk.
If the render pass was rendered from many cameras of a camera set (stereoscopy), the file sequences of each render camera are imported in the same render pass composition, each with it own Import node and output node. The name of the output nodes is suffixed by its corresponding camera name. The camera anchor is set on the output node.
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Note: Unlike other footage compositions which have an Original Footage and a working version, a render pass composition initially has only one version, the working version.
A render pass composition update can be started when there is a new version of the rendered files on disk (includes changes to the rendered files path, the frame range, their image format, the OpenEXR channels the pass is stored in if any, etc.).
When updating a render pass composition, a new empty version of the render pass composition is created if you turned on the Backup Version option in the Pre-Compositing Import dialog box, and the new render pass file sequence is imported the same way it is done in the creation process--see The Pre-Compositing Import Options.
Note that the primary version of a render pass composition is never changed by the pre-compositing update. It is up to you to decide which one is the primary.
Before the render layer composition is created, render pass compositions for the given render layer are created or updated.
With a Template--If a template is specified for the render layer, its content is copied into the render layer composition and the rest of the operations applied to it are quite similar to what happens during an update.
The dependency graph is reviewed to find all the render pass anchor link nodes which are updated to link to their associated render pass composition, which was previously created or updated.
If some render pass anchor link nodes are missing in the template, new unconnected render pass anchor link nodes are automatically added to the render layer composition (in the same way as when no template is specified).
Without a Template--If no template is specified, the render layer composition is created with a single unconnected output node. For each render pass composition, there is an unconnected link node that points to it.
The render pass link nodes have their anchors automatically set to their corresponding render pass anchor name and the nodes are initially named after their linked render pass compositions (their names are not changed by further updates).
What Happens Next?-- By default, a render pass anchor link node points to the Latest version. This is because a new render pass composition version was added during a pre-comp file update is not automatically tagged as the primary version. Choosing the primary render pass version is up to you. If you want the render layer composition to be updated automatically when new Maya render passes are imported in Toxik, the render pass anchor link nodes must point to their latest version by default--see broken-link (Beta).
The image format, pixel format and rate of the render layer composition are set according to the information contained in the pre-comp file.
The time range (start, end) of the render layer composition is then set to the union of its render pass compositions time ranges.
A render layer composition is updated when a new pass is added to the scene. Deleting a pass will not trigger an update because it's non-destructive. Renaming a pass is equivalent to adding a new pass.
The working version of the render layer composition is backed up if you set the Backup Version option. Then, in Update mode, the working version is updated. otherwise it is recreated from scratch (Recreate mode).
Updating the render layer composition is then quite straightforward. Existing render pass anchor link nodes are left unchanged because they point to the latest version of the render pass composition by default. The ones that are missing are created (but are unconnected) and linked to their respective render pass compositions.
If an existing render pass is no longer in the render layer (which could be because it was removed from the 3D scene or because the pre-comp file update is partial), its anchor link node is not deleted; the render layer composition update is non-destructive--see Non-Destructive Updates.
The format and rate of a render layer composition is not modified on update. However, the start/end of the render layer composition is updated to be the union of its current time range and the time ranges of all its linked render pass compositions.
Before the scene composition is created, render layer compositions in the scene composition are created or updated.
With a Template--If a template is specified for the scene, its content is copied into the scene composition and the rest of the operations applied to it are quite similar to what happens during an update of the scene.
The dependency graph is reviewed to find all the render layer anchor link nodes which are updated to link to their associated render layer composition, which was previously created or updated.
If some render layer anchor link nodes are missing in the scene template, new unconnected render layer link nodes are automatically added to the scene composition (in the same way as when no template is specified).
Without a Template--If no scene template is specified, render layer anchor link nodes are created with their proper anchor name set and point to their respective render layer composition. Render layers are then stacked in a chain of Blend and Comp nodes, respecting the compositing order and blend modes used in the 3D scene.
What Happens Next?--The render layer link nodes have their anchors automatically set to their corresponding render layer anchor name and the nodes are initially named after their linked render layer compositions (their names are not changed by further updates).
The image format, pixel format, and the rate of the scene composition are then set according to the default render settings of the 3D scene. The time range (start, end) of the scene composition is then set to the union of its render layer compositions time ranges.
A scene composition is updated when a new layer is added to the scene. Deleting a layer will not trigger an update because it's non-destructive. Renaming a layer is equivalent to adding a new layer.
The working version of the scene composition is backed up if you set the Backup Version option. Then, in Update mode, the working version is updated. otherwise it is recreated from scratch (Recreate mode).
Existing render layer anchor link nodes are left unchanged because they point to the latest version of the render layer composition by default. The ones that are missing are created and linked to their respective render layer compositions.
If an existing render layer is no longer in the scene (because it was removed from the 3D scene or because the pre-comp file update is partial), its anchor link node is not deleted; the scene composition update is non-destructive--see Non-Destructive Updates.
If the layer ordering or the blend modes between layers have changed, a new stack of Blend & Comp nodes is created within a visual group next to the old stack. In the following example, the tire and tire label layers were added during update.
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The format and rate of a scene composition is not modified on update. However, the start/end of the scene composition is updated to be the union of its current time range and the time ranges of all its linked render layer compositions.
In a stereoscopic scene, rendered files produced by each camera of the stereo rig are imported and composited in the same composition at all levels (pass, layer and scene). There are two modes in which you import a stereo scene, either in multi-stream mode or not--see The Pre-Compositing Import Options.
In single stream, the graph of the template is duplicated for each camera and placed within a group node to avoid name and expression clashes. The left and right of the output link nodes feed the corresponding dependency graph.
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For example, if you double-click the left group, you'll see the default render layer template in the following dependency graph.
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In Multi-Stream mode, the left and right outputs of each link node are merged together, feeding only one instance of the dependency graph. At the end, each stream is extracted--see Multi-stream Compositing.
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By default, each layer of a scene is imported into a different render layer composition. For greater compositing freedom and to set expressions, you must have all the dependency graphs of each layer in one scene composition.
To merge layers during import, click the Merge button in the Pre-Compositing Import Options dialog box. The following shows what a scene composition would look like after merging layers. Notice that each layer is represented by the same dependency graph because they all use the same default template.
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You can also specify a template to handle all passes from all layers--see Using Pre-Compositing Templates.
You can replace a link node by the content of its linked composition.
In the Schematic view, right-click a Link Image node and select Merge and one of the following:
Non-Recursive: Bring in one level of the linked composition.
Recursive: Apply the merge recursively on all link nodes found in the linked composition version.
Recursive Except Footage: Stop recursion at footage compositions.
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