MassFX Tools - World Panel

Scene Settings rollout

Use Ground Plane: When on, MassFX uses an (invisible) infinite static rigid body at Z=0; that is, coplanar with the home grid. This body has fixed values for friction and bounciness. Default=on.
TipUse the ground plane as a handy testbed for your simulations.

Gravity group

Gravity Enabled: When on, all rigid bodies with Use Gravity activated are subject to gravity.
Direction: The global axis along which gravity (see Acceleration, following) is applied. For standard up/down gravity, set Direction to Z; this is the default.
Acceleration: The force of gravity, specified in units per second per second. Using the Z axis, positive values cause gravity to pull objects upward, while negative values pull objects downward (the standard effect).
For reference, Earth's gravity is approximately -981.001 cm/s² = -386.221 in/s² = -32.185 ft/s² = -9.81 m/s²

Rigid Bodies group

Substeps: The number of simulation steps performed between each graphical update is determined by this formula: (Substeps + 1) * Frame Rate. A frame rate of 30fps with 0 substeps results in 30 simulation steps per second, 1 substep results in 60 steps per second, 2 substeps results in 180 simulation steps per second, and so on. The maximum value of Substeps is 159, which results in 4,800 simulation steps per second of animation at 30fps. Using a higher Substeps value produces greater precision in collision and constraint results, at a cost to performance, of course.
Solver Iter[ations]: A global setting for the number of times the constraint solver enforces collisions and constraints. Higher values might be necessary when the simulation uses many constraints, or the tolerance for joint errors is very low. Values higher than 30 are generally unnecessary.
Collision Overlap: The distance that rigid bodies are allowed to overlap.
An excessively high value can cause objects to interpenetrate visibly. Setting this value too low can cause jittering because objects alternate between interpenetrating one frame and being forcibly separated the next.

The best value depends upon variety of factors, including the size of objects in the scene, the proximity of the camera to possible interpenetrations, the settings for Gravity Acceleration and Solver Iterations, the inflation amount of the physical meshes, and the frame rate of the simulation.
Use High Velocity Collisions: A global setting for toggling continuous collision detection.
When rigid bodies are moving so fast that they travel a large distance from one simulation frame to the next, they can "tunnel" through one another. For example, a fast-moving bowling ball in an animation that uses a low frame rate might be on one side of a pin at one frame and move to the other side of the pin in the next. In such a case, the desired collision between the ball and the pin does not occur.

This can be fixed by increasing the frame rate and/or substeps of the simulation. However, these settings apply globally; increasing them enough to fix one fast-moving object can reduce the performance of the entire simulation. When Use High Velocity Collisions is on, MassFX finds any fast-moving rigid bodies and creates a simplified collision shape spanning the position between the previous frame and the current frame. For example, the bowling ball could have a capsule stretching from one side of the pin to the other; because the capsule overlaps the pin, MassFX detects the collision.

By default, MassFX sets the threshold speed above which it applies Use High Velocity Collisions for rigid bodies heuristically (that is, based on experiential data). To specify a custom value, use the High Velocity Collisions Min Speed setting.

NoteThis mode applies only to a limited set of collision circumstances. The dynamic rigid body must also have Use High Velocity Collisions enabled, be moving faster the Min Speed threshold, and colliding with a static rigid body that uses a convex hull for the physical mesh.

Advanced Settings rollout

Sleep Settings group

[sleep method]

Rigid bodies in the simulation moving slower than a certain rate automatically go into "sleep" mode, which improves performance by letting MassFX tend to other, more active objects. Sleeping objects "wake up" if bumped by another non-sleeping rigid body.

Choose how MassFX determines when a body sleeps:

AutomaticMassFX automatically calculates reasonable sleep threshold values for both linear and angular velocities above which sleep will be applied. To do so it uses a heuristic, or experience-based, method.
ManualTo override the heuristic values for speed and spin, choose Manual and adjust the following settings as necessary:

Min Speed

When Manual is chosen, rigid bodies in the simulation traveling slower than this speed (specified in units/second) automatically enter "sleep" mode.

Setting this value too high can cause obviously moving objects to stop suddenly when their speed drops below this value. Setting this value too low will cause fewer objects to sleep. Setting Min Speed value to 0.0 disables sleeping altogether.

Min Spin

Rigid bodies in the simulation rotating slower than this speed (specified in degrees/second) automatically enter "sleep" mode.

Setting this value to 0.0 disables sleeping altogether.

High Velocity Collisions group

[high velocity collisions method]

When Use High Velocity Collisions is on, these settings determine how MassFX calculates such collisions. Choose a method:

AutomaticMassFX uses a heuristic algorithm to calculate a reasonable speed threshold value above which the high-velocity-collision method is applied.
ManualTo override the automatic value for speed, choose Manual and set the desired Min Speed value:

Min Speed

Rigid bodies in the simulation moving faster than this speed (specified in units/second) automatically go into high-velocity-collision mode. Setting this value too high may cause fast-moving objects to tunnel through objects with which it should instead collide. Setting this value too low will cause more objects to go into high-velocity-collision mode, which may reduce performance as additional computation is required to calculate collision for slow-moving objects. Setting this value to 0.0 enables high-velocity-collision mode for all moving objects. For these settings to be applied, Use High Velocity Collisions must be on.

Bounce Settings group

[bounce method]

Choose a method for determining when rigid bodies bounce off each other:

AutomaticMassFX uses a heuristic algorithm to calculate a reasonable minimum speed threshold above which to apply bounce.
ManualTo override the heuristic value for speed, choose Manual and set the desired Min Speed value:

Min Speed

Rigid bodies in the simulation moving faster than this speed (specified in units/second) will bounce off one another as part of a collision. Setting this value too high will cause fast-moving objects not to bounce upon colliding with another object. Setting this value too low will cause more slow-moving objects to bounce around the scene, reducing simulation performance and possibly causing jittering. Setting this value to 0.0 enables bouncing for all moving objects.

Simulation Settings rollout

On Last Frame

Choose whether and how the simulation is to proceed upon reaching the last frame of the animation:

Continue SimulationThe simulation continues to run even after the time slider reaches the last frame.
Stop SimulationThe simulation stops when the time slider reaches the last frame.
Loop Animation and ...Choose this to repeat the animation when the time slider reaches the last frame. Two options are available:
- Reset SimulationThe simulation resets and the animation loops back to the first frame when the time slider reaches the last frame. This is useful for watching the same simulation multiple times in a row to analyze the results.
- Continue SimulationThe simulation continues running while the animation loops back to the first frame when the time slider reaches the last frame. This is useful for short looping animations (such as a character's walk cycle) when you want the simulation to continue across the boundary of the looping.

Engine rollout

These options can speed up the simulation if you have the required hardware.

ImportantUsing either or both of these options might improve performance slightly. However, when they are enabled, the simulation is not deterministic, meaning that every simulation run will produce different results. We recommend that you avoid this problem by leaving the options disabled, as the performance difference is often not substantial.

Use Multithreading: When on, if your CPU contains multiple cores, the CPU can execute multiple threads for faster calculation of the simulation. This can improve performance under some circumstances; however, the results between successive simulations can vary.
Hardware Acceleration: When on, if your system is equipped with an Nvidia GPU, your system can use hardware acceleration to perform certain computations. This can improve performance under some circumstances; however, the results between successive simulations can vary.
About MassFX: Opens a small dialog showing basic information about MassFX, including the PhysX version.