Bullet questions

[Leadwerks]

Does bullet have a function to retrieve all the triangles of a polygon mesh that intersect an AABB?

Do bullet heightfield terrains use two bytes per terrain point so that a 4096x4096 terrain uses about 33 mb memory?

How good is the character controller? Be honest. How much work will I have to put into getting it to work right so that it can push and be pushed by other bodies, not slide down slopes under ascertain steepness, etc.

How good is the multi body vehicle? I have had bad results with ray cast vehicles in other libraries in the past.

Are joint limits and motors built into most joint classes?

What is the extent of the opencl integration? I only saw a particle demo that used this.
Thank you for your answers.

[Erwin Coumans]

Does bullet have a function to retrieve all the triangles of a polygon mesh that intersect an AABB?

Yes. See btBvhTriangleMeshShape::processAllTriangles method.

Do bullet heightfield terrains use two bytes per terrain point so that a 4096x4096 terrain uses about 33 mb memory?

Yes, this is possible. Create a btHeightfieldTerrainShape with the scalar type PHY_SHORT (other options are PHY_FLOAT).
See http://code.google.com/p/bullet/source/ ... ainShape.h

How good is the character controller? Be honest.

It is crap and someone needs to rewrite it.

How good is the multi body vehicle? I have had bad results with ray cast vehicles in other libraries in the past.

There is no multi body vehicle. There is only a btRaycastVehicle and joints such as btHinge2Constraint that allow you to create a custom vehicle. For fast moving vehicles, btRaycastVehicles are recommended. Otherwise you need to write your own vehicle simulation.

Are joint limits and motors built into most joint classes?

btHingeConstraint, btSliderConstraint and btGeneric6DofConstraint have motors.

What is the extent of the opencl integration? I only saw a particle demo that used this.

Bullet 2.78 has a particle demo and a cloth demo using OpenCL. We are working on OpenCL and DX11 DirectCompute acceleration for collision detection and rigid body dynamics for Bullet 3.x.
Thanks,
Erwin

[Leadwerks]

It is crap and someone needs to rewrite it.

Thanks! At least I know what to expect. I've found in the past it's very hard to use angular physics with a character controller, because no matter what force or constraint you use to right the controller, it's always going to have other unintended effects. I've had the best luck writing my own simple velocity physics and detecting collisions with a static shape that isn't physically active, then applying force to the bodies it collides with, and processing the velocity of the controller myself. This allows a controller that affects and is affected by other bodies, while maintaining the stability and smoothness of old-school FPS collision detection.