Bullet Known Limitations

The following are the known limitations for this version of Bullet plug-in.

General

• Bullet nodes must have unique names to avoid namespace conflicts.
• Bullet's internal units are in metric (meters) and do not perform correctly when Imperial measurements are used. If the Imperial system is required, maintain system units in centimeters and then change the physics settings to compensate, such as changing Maya Gravity settings from 9.8 to 980 kg for mass changed from 1kg to 1000kg.
• After duplicating Bullet objects, you may need to rewind to start frame of the Maya timeline to see the correct result.
• The Bullet node structure not ideal for modifying or deleting.
• The soft body OpenCL solver acceleration is experimental and has a number of important limitations. The OpenCL soft body acceleration is limited to cloth and not volumetric objects. It only supports interaction with rigid bodies with capsule collision shapes. There is no interaction between other cloth bodies or between rigid bodies. The interaction between cloth and rigid bodies is one way meaning, a rigid body can influence soft body but a soft body cannot influence a rigid body.
• Bullet 2.8.1 OpenCL acceleration does not support soft body to soft body collisions.
• Bullet 2.8.1 OpenCL CPU and GPU accelerated solvers only support capsule as the Collider Shape Type. Other Collider Shape Types are not be recognized by these solvers.
• Bullet 3.0 - there are some limitations if you enable this version of Bullet. See Bullet v3.0.

Bullet Solver

• Bullet Alembic Export does not support workflows where the geometry has had scaling applied. Remove any scaling and/or local pivot from objects before attaching the Bullet Solver to the object.
• Bullet nodes may not appear correctly in the viewport if the Maya timeline is not rewound to frame 1. This occurs because the solver needs to be reinitialized to recognize new objects. New objects in the scene are reinitialized at frame 1 of the Maya timeline.
• The output from the Bullet solver Debug Draw for collisions between soft bodies and plane collider shapes may appear erratic. This occurs because Bullet renders a yellow wire-frame for the triangles that represent the projection of the soft body's axis-aligned bounding box onto the plane. This is the expected behavior. It may be easier to visualize the collisions by viewing the scene from the Top perspective viewport.

  Bullet 2.81 Soft Body OpenCL solver acceleration has a number of restrictions. You can only use OpenCL soft body acceleration with cloth, not volumetric objects and it only supports interaction with rigid bodies that have capsule collision shape types. You cannot have interaction between other cloth bodies or between rigid bodies. Cloth and rigid body interaction only works in direction, so that while a rigid body can influence soft body, a soft body cannot influence a rigid body.

• The Bullet Solver Wind Magnitude and Wind Direction setting applies only to soft bodies.

Rigid Body, Soft Body, and Ragdoll

• Due to a problem with Alembic caching, you cannot re-import an alembic cache if the objects in the render scene have namespaces.
• Output meshes with per-facet shaders cannot locate the bulletSoftBodyShape node when setting the per-particle particleMass attribute. As a workaround, use the source mesh to set the per-particle particleMass attribute.
• Ragdoll does not collapse as if the pieces are properly joined.
• Active rigid bodies and rigid sets will not simulate accurately if you freeze translate and rotate transforms values.
• If a static rigid body has an associated animated rigid body, Bullet treats the static rigid body as a kinematic rigid body internally. This means that the optimization by the solver for static rigid body is disabled. As a workaround, go to the Maya timeline start frame and replay the simulation.
• Setting the Linear Constraint X, Y, and Z attribute to Locked may not lock the constraint completely along this specified axis. if the constraint bodies collide they may impart forces.
• The Limits attributes for rigid body constraints may not work properly; the Solver acceleration affects soft bodies only.
• AbcBulletExport: Specify the exact file path when exporting as Maya does not add the suffix file extension .abc automatically.
• ABC file Import: Make sure that you freeze the transforms on objects before importing your ABC file. The ABC file contains only translation and rotation animation and doesn't have the scale or rotation pivot information.
• After loading a saved scene, reset the initial state nodes before Alembic export (using the AbcBullet). Otherwise there may a mismatch between the exported node names and the associated transforms.