btConvexTriangleMeshShape.cpp

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/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2009 Erwin Coumans  http://bulletphysics.org
 
This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, 
including commercial applications, and to alter it and redistribute it freely, 
subject to the following restrictions:
 
1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
 
#include "btConvexTriangleMeshShape.h"
#include "BulletCollision/CollisionShapes/btCollisionMargin.h"
 
#include "LinearMath/btQuaternion.h"
#include "BulletCollision/CollisionShapes/btStridingMeshInterface.h"
 
btConvexTriangleMeshShape ::btConvexTriangleMeshShape(btStridingMeshInterface* meshInterface, bool calcAabb)
    : btPolyhedralConvexAabbCachingShape(), m_stridingMesh(meshInterface)
{
    m_shapeType = CONVEX_TRIANGLEMESH_SHAPE_PROXYTYPE;
    if (calcAabb)
        recalcLocalAabb();
}
 
class LocalSupportVertexCallback : public btInternalTriangleIndexCallback
{
    btVector3 m_supportVertexLocal;
 
public:
    btScalar m_maxDot;
    btVector3 m_supportVecLocal;
 
    LocalSupportVertexCallback(const btVector3& supportVecLocal)
        : m_supportVertexLocal(btScalar(0.), btScalar(0.), btScalar(0.)),
          m_maxDot(btScalar(-BT_LARGE_FLOAT)),
          m_supportVecLocal(supportVecLocal)
    {
    }
 
    virtual void internalProcessTriangleIndex(btVector3* triangle, int partId, int triangleIndex)
    {
        (void)triangleIndex;
        (void)partId;
 
        for (int i = 0; i < 3; i++)
        {
            btScalar dot = m_supportVecLocal.dot(triangle[i]);
            if (dot > m_maxDot)
            {
                m_maxDot = dot;
                m_supportVertexLocal = triangle[i];
            }
        }
    }
 
    btVector3 GetSupportVertexLocal()
    {
        return m_supportVertexLocal;
    }
};
 
btVector3 btConvexTriangleMeshShape::localGetSupportingVertexWithoutMargin(const btVector3& vec0) const
{
    btVector3 supVec(btScalar(0.), btScalar(0.), btScalar(0.));
 
    btVector3 vec = vec0;
    btScalar lenSqr = vec.length2();
    if (lenSqr < btScalar(0.0001))
    {
        vec.setValue(1, 0, 0);
    }
    else
    {
        btScalar rlen = btScalar(1.) / btSqrt(lenSqr);
        vec *= rlen;
    }
 
    LocalSupportVertexCallback supportCallback(vec);
    btVector3 aabbMax(btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT));
    m_stridingMesh->InternalProcessAllTriangles(&supportCallback, -aabbMax, aabbMax);
    supVec = supportCallback.GetSupportVertexLocal();
 
    return supVec;
}
 
void btConvexTriangleMeshShape::batchedUnitVectorGetSupportingVertexWithoutMargin(const btVector3* vectors, btVector3* supportVerticesOut, int numVectors) const
{
    //use 'w' component of supportVerticesOut?
    {
        for (int i = 0; i < numVectors; i++)
        {
            supportVerticesOut[i][3] = btScalar(-BT_LARGE_FLOAT);
        }
    }
 
 
    for (int j = 0; j < numVectors; j++)
    {
        const btVector3& vec = vectors[j];
        LocalSupportVertexCallback supportCallback(vec);
        btVector3 aabbMax(btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT));
        m_stridingMesh->InternalProcessAllTriangles(&supportCallback, -aabbMax, aabbMax);
        supportVerticesOut[j] = supportCallback.GetSupportVertexLocal();
    }
}
 
btVector3 btConvexTriangleMeshShape::localGetSupportingVertex(const btVector3& vec) const
{
    btVector3 supVertex = localGetSupportingVertexWithoutMargin(vec);
 
    if (getMargin() != btScalar(0.))
    {
        btVector3 vecnorm = vec;
        if (vecnorm.length2() < (SIMD_EPSILON * SIMD_EPSILON))
        {
            vecnorm.setValue(btScalar(-1.), btScalar(-1.), btScalar(-1.));
        }
        vecnorm.normalize();
        supVertex += getMargin() * vecnorm;
    }
    return supVertex;
}
 
//currently just for debugging (drawing), perhaps future support for algebraic continuous collision detection
//Please note that you can debug-draw btConvexTriangleMeshShape with the Raytracer Demo
int btConvexTriangleMeshShape::getNumVertices() const
{
    //cache this?
    return 0;
}
 
int btConvexTriangleMeshShape::getNumEdges() const
{
    return 0;
}
 
void btConvexTriangleMeshShape::getEdge(int, btVector3&, btVector3&) const
{
    btAssert(0);
}
 
void btConvexTriangleMeshShape::getVertex(int, btVector3&) const
{
    btAssert(0);
}
 
int btConvexTriangleMeshShape::getNumPlanes() const
{
    return 0;
}
 
void btConvexTriangleMeshShape::getPlane(btVector3&, btVector3&, int) const
{
    btAssert(0);
}
 
//not yet
bool btConvexTriangleMeshShape::isInside(const btVector3&, btScalar) const
{
    btAssert(0);
    return false;
}
 
void btConvexTriangleMeshShape::setLocalScaling(const btVector3& scaling)
{
    m_stridingMesh->setScaling(scaling);
 
    recalcLocalAabb();
}
 
const btVector3& btConvexTriangleMeshShape::getLocalScaling() const
{
    return m_stridingMesh->getScaling();
}
 
void btConvexTriangleMeshShape::calculatePrincipalAxisTransform(btTransform& principal, btVector3& inertia, btScalar& volume) const
{
    class CenterCallback : public btInternalTriangleIndexCallback
    {
        bool first;
        btVector3 ref;
        btVector3 sum;
        btScalar volume;
 
    public:
        CenterCallback() : first(true), ref(0, 0, 0), sum(0, 0, 0), volume(0)
        {
        }
 
        virtual void internalProcessTriangleIndex(btVector3* triangle, int partId, int triangleIndex)
        {
            (void)triangleIndex;
            (void)partId;
            if (first)
            {
                ref = triangle[0];
                first = false;
            }
            else
            {
                btScalar vol = btFabs((triangle[0] - ref).triple(triangle[1] - ref, triangle[2] - ref));
                sum += (btScalar(0.25) * vol) * ((triangle[0] + triangle[1] + triangle[2] + ref));
                volume += vol;
            }
        }
 
        btVector3 getCenter()
        {
            return (volume > 0) ? sum / volume : ref;
        }
 
        btScalar getVolume()
        {
            return volume * btScalar(1. / 6);
        }
    };
 
    class InertiaCallback : public btInternalTriangleIndexCallback
    {
        btMatrix3x3 sum;
        btVector3 center;
 
    public:
        InertiaCallback(btVector3& center) : sum(0, 0, 0, 0, 0, 0, 0, 0, 0), center(center)
        {
        }
 
        virtual void internalProcessTriangleIndex(btVector3* triangle, int partId, int triangleIndex)
        {
            (void)triangleIndex;
            (void)partId;
            btMatrix3x3 i;
            btVector3 a = triangle[0] - center;
            btVector3 b = triangle[1] - center;
            btVector3 c = triangle[2] - center;
            btScalar volNeg = -btFabs(a.triple(b, c)) * btScalar(1. / 6);
            for (int j = 0; j < 3; j++)
            {
                for (int k = 0; k <= j; k++)
                {
                    i[j][k] = i[k][j] = volNeg * (btScalar(0.1) * (a[j] * a[k] + b[j] * b[k] + c[j] * c[k]) + btScalar(0.05) * (a[j] * b[k] + a[k] * b[j] + a[j] * c[k] + a[k] * c[j] + b[j] * c[k] + b[k] * c[j]));
                }
            }
            btScalar i00 = -i[0][0];
            btScalar i11 = -i[1][1];
            btScalar i22 = -i[2][2];
            i[0][0] = i11 + i22;
            i[1][1] = i22 + i00;
            i[2][2] = i00 + i11;
            sum[0] += i[0];
            sum[1] += i[1];
            sum[2] += i[2];
        }
 
        btMatrix3x3& getInertia()
        {
            return sum;
        }
    };
 
    CenterCallback centerCallback;
    btVector3 aabbMax(btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT));
    m_stridingMesh->InternalProcessAllTriangles(&centerCallback, -aabbMax, aabbMax);
    btVector3 center = centerCallback.getCenter();
    principal.setOrigin(center);
    volume = centerCallback.getVolume();
 
    InertiaCallback inertiaCallback(center);
    m_stridingMesh->InternalProcessAllTriangles(&inertiaCallback, -aabbMax, aabbMax);
 
    btMatrix3x3& i = inertiaCallback.getInertia();
    i.diagonalize(principal.getBasis(), btScalar(0.00001), 20);
    inertia.setValue(i[0][0], i[1][1], i[2][2]);
    inertia /= volume;
}