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Remove first argument from btMultiSphereShape, calculate local inertia approximation from aabb.

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If user wants more accurate inertia tensor for multi-sphere shape, use btCompoundShape instead 
(amd btCompoundShape::calculatePrincipalAxisTransform)

Thanks rcharlton for bringing this up.
Erwin
This commit is contained in:
erwin.coumans
2009-06-11 13:51:48 +00:00
parent 6c80353556
commit f552a1dbbf
4 changed files with 17 additions and 35 deletions
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2
Demos/CharacterDemo/DynamicCharacterController.cpp
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@@ -33,7 +33,7 @@ void DynamicCharacterController::setup (btScalar height, btScalar width, btScala
m_halfHeight = height/btScalar(2.0);
m_shape = new btMultiSphereShape (btVector3(width/btScalar(2.0), height/btScalar(2.0), width/btScalar(2.0)), &spherePositions[0], &sphereRadii[0], 2);
m_shape = new btMultiSphereShape (&spherePositions[0], &sphereRadii[0], 2);
btTransform startTransform;
startTransform.setIdentity ();

34
src/BulletCollision/CollisionShapes/btMultiSphereShape.cpp
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@@ -19,8 +19,8 @@ subject to the following restrictions:
#include "BulletCollision/CollisionShapes/btCollisionMargin.h"
#include "LinearMath/btQuaternion.h"
btMultiSphereShape::btMultiSphereShape (const btVector3& inertiaHalfExtents,const btVector3* positions,const btScalar* radi,int numSpheres)
:btConvexInternalAabbCachingShape (), m_inertiaHalfExtents(inertiaHalfExtents)
btMultiSphereShape::btMultiSphereShape (const btVector3* positions,const btScalar* radi,int numSpheres)
:btConvexInternalAabbCachingShape ()
{
m_shapeType = MULTI_SPHERE_SHAPE_PROXYTYPE;
btScalar startMargin = btScalar(BT_LARGE_FLOAT);
@@ -39,8 +39,6 @@ btMultiSphereShape::btMultiSphereShape (const btVector3& inertiaHalfExtents,cons
}
btVector3 btMultiSphereShape::localGetSupportingVertexWithoutMargin(const btVector3& vec0)const
{
int i;
@@ -125,27 +123,17 @@ void btMultiSphereShape::calculateLocalInertia(btScalar mass,btVector3& inertia)
{
//as an approximation, take the inertia of the box that bounds the spheres
btTransform ident;
ident.setIdentity();
// btVector3 aabbMin,aabbMax;
btVector3 localAabbMin,localAabbMax;
getCachedLocalAabb(localAabbMin,localAabbMax);
btVector3 halfExtents = (localAabbMax-localAabbMin)*btScalar(0.5);
// getAabb(ident,aabbMin,aabbMax);
btScalar lx=btScalar(2.)*(halfExtents.x());
btScalar ly=btScalar(2.)*(halfExtents.y());
btScalar lz=btScalar(2.)*(halfExtents.z());
btVector3 halfExtents = m_inertiaHalfExtents;//(aabbMax - aabbMin)* btScalar(0.5);
btScalar margin = CONVEX_DISTANCE_MARGIN;
btScalar lx=btScalar(2.)*(halfExtents[0]+margin);
btScalar ly=btScalar(2.)*(halfExtents[1]+margin);
btScalar lz=btScalar(2.)*(halfExtents[2]+margin);
const btScalar x2 = lx*lx;
const btScalar y2 = ly*ly;
const btScalar z2 = lz*lz;
const btScalar scaledmass = mass * btScalar(.08333333);
inertia[0] = scaledmass * (y2+z2);
inertia[1] = scaledmass * (x2+z2);
inertia[2] = scaledmass * (x2+y2);
inertia.setValue(mass/(btScalar(12.0)) * (ly*ly + lz*lz),
mass/(btScalar(12.0)) * (lx*lx + lz*lz),
mass/(btScalar(12.0)) * (lx*lx + ly*ly));
}

10
src/BulletCollision/CollisionShapes/btMultiSphereShape.h
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@@ -22,21 +22,15 @@ subject to the following restrictions:
#include "LinearMath/btAabbUtil2.h"
///The btMultiSphereShape represents the convex hull of a collection of spheres. You can create special capsules or other smooth volumes.
///It is possible to animate the spheres for deformation.
///It is possible to animate the spheres for deformation, but call 'recalcLocalAabb' after changing any sphere position/radius
class btMultiSphereShape : public btConvexInternalAabbCachingShape
{
btAlignedObjectArray<btVector3> m_localPositionArray;
btAlignedObjectArray<btScalar> m_radiArray;
btVector3 m_inertiaHalfExtents;
public:
btMultiSphereShape (const btVector3& inertiaHalfExtents,const btVector3* positions,const btScalar* radi,int numSpheres);
btMultiSphereShape (const btVector3* positions,const btScalar* radi,int numSpheres);
///CollisionShape Interface
virtual void calculateLocalInertia(btScalar mass,btVector3& inertia) const;

4
src/BulletDynamics/Dynamics/Bullet-C-API.cpp
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@@ -181,12 +181,12 @@ plCollisionShapeHandle plNewBoxShape(plReal x, plReal y, plReal z)
plCollisionShapeHandle plNewCapsuleShape(plReal radius, plReal height)
{
//capsule is convex hull of 2 spheres, so use btMultiSphereShape
btVector3 inertiaHalfExtents(radius,height,radius);
const int numSpheres = 2;
btVector3 positions[numSpheres] = {btVector3(0,height,0),btVector3(0,-height,0)};
btScalar radi[numSpheres] = {radius,radius};
void* mem = btAlignedAlloc(sizeof(btMultiSphereShape),16);
return (plCollisionShapeHandle) new (mem)btMultiSphereShape(inertiaHalfExtents,positions,radi,numSpheres);
return (plCollisionShapeHandle) new (mem)btMultiSphereShape(positions,radi,numSpheres);
}
plCollisionShapeHandle plNewConeShape(plReal radius, plReal height)
{