Search found 10 matches

by paul.dubois
Fri Nov 12, 2010 7:43 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Is there anyway around quaternions for setting orientation?
Replies: 2
Views: 1959

Re: Is there anyway around quaternions for setting orientati

First ask yourself why you are inventing your own orientation representation (Directional vector + Up vector) rather than using an existing representation. There are many to choose from. If you don't feel like learning quaternions, consider using a 3x3 matrix. Your representation is very much like a...
by paul.dubois
Tue Nov 02, 2010 1:39 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: btQuaternion clamping values and slerp question
Replies: 3
Views: 2569

Re: btQuaternion clamping values and slerp question

btQuat::angle actually measures the angle between the two 4d quaternions, not the angle you'd get if you converted the quat to an axis-angle format. An odd feature of quaternions is that every orientation is specified by two distinct quaternions: (x,y,z,w) and (-x,-y,-z,-w). These two quaternions ar...
by paul.dubois
Fri Oct 29, 2010 7:13 pm
Forum: General Bullet Physics Support and Feedback
Topic: allowedCcdPenetration questions
Replies: 2
Views: 1941

allowedCcdPenetration questions

A couple questions about allowedCcdPenetration. What is the intent of allowedCcdPenetration? Is it designed to improve gjk stability, or perhaps to allow the user to ignore grazing contacts? Or am I on the wrong track here? Also, what is the expected effect? I previously thought it was something lik...
by paul.dubois
Thu Oct 14, 2010 3:06 am
Forum: Release Announcements
Topic: Sony Vector Math library and SIMD math library open sourced
Replies: 5
Views: 60941

Re: Sony Vector Math library and SIMD math library open sour

If the architecture, abi, compiler, and math library all cooperate, then returning a vector by value is cheap -- it goes in a register. Also, the less aliasing means more opportunities for the compiler to optimize. It's not OK for the api to change between the scalar and simd implementations (the ch...
by paul.dubois
Tue Sep 28, 2010 11:52 pm
Forum: General Bullet Physics Support and Feedback
Topic: btDispatcher::dispatchAllCollisionPairs
Replies: 2
Views: 2092

btDispatcher::dispatchAllCollisionPairs

Is there a subtle reason btDispatcher::dispatchAllCollisionPairs() takes a btDispatcher* parameter? void btCollisionDispatcher::dispatchAllCollisionPairs( btOverlappingPairCache* pairCache, const btDispatcherInfo& dispatchInfo, btDispatcher* dispatcher) { btCollisionPairCallback collisionCallback(di...
by paul.dubois
Wed Jun 16, 2010 6:44 pm
Forum: General Bullet Physics Support and Feedback
Topic: MOPP analogue
Replies: 2
Views: 1279

Re: MOPP analogue

* Use btCompoundShape with optional dbvt. CON: ray and sweep tests don't use the acceleration structure ( issue 25 ). Also, seems like a slight abuse of shapes; nobody will care about the combined inertia tensor, for example. Issue 25 looks easy for me to implement, but it _has_ been sitting around...
by paul.dubois
Tue Jun 15, 2010 12:57 am
Forum: General Bullet Physics Support and Feedback
Topic: internalSetTemporaryCollisionShape necessary?
Replies: 0
Views: 832

internalSetTemporaryCollisionShape necessary?

I'm looking at issue 25 now. I notice that rayTestSingle mutates the passed collisionObject by calling internalSetTemporaryCollisionShape. Is this still necessary any more? It looks like the btCompoundShape recursive case already explicitly passes down all the information it needs through collisionS...
by paul.dubois
Sat Jun 12, 2010 12:40 am
Forum: General Bullet Physics Support and Feedback
Topic: MOPP analogue
Replies: 2
Views: 1279

MOPP analogue

We divide our large world into chunks and wrap all static collision for a chunk into a Hk MOPP. The broadphase contains only a couple static objects -- one for the MOPP, one with a custom heightfield shape. There seem to be a few possiblilities to do this this in Bullet. * Forget the container; batc...
by paul.dubois
Wed Jun 02, 2010 12:29 am
Forum: General Bullet Physics Support and Feedback
Topic: Pose matching with direct angular velocity control
Replies: 3
Views: 1748

Re: Pose matching with direct angular velocity control

Thanks! I can successfully create spring-like behavior, but I am having trouble figuring out exactly what parameters will result in the pose being 100% matched, 50% matched, and so on, so that I can control it in a precise way. If you want the object to move N% of the way to the goal during a fixed...
by paul.dubois
Fri May 28, 2010 12:25 am
Forum: General Bullet Physics Support and Feedback
Topic: Quick Q: XDK and/or PS3 SDK project generation
Replies: 1
Views: 994

Quick Q: XDK and/or PS3 SDK project generation

Is there some way to get CMake to generate project files for use with the XDK and/or PS3 SDK? Or is everyone who needs them writing them by hand?