/** Helper to transform a normal when non-uniform scale is present. */
static PxVec3 TransformNormalToShapeSpace(const PxMeshScale& meshScale, const PxVec3& nIn)
{
// Uniform scale makes this unnecessary
if (meshScale.scale.x == meshScale.scale.y &&
meshScale.scale.x == meshScale.scale.z)
{
return nIn;
}
if (PxQuatIsIdentity(meshScale.rotation))
{
// Inverse transpose: inverse is 1/scale, transpose = original when rotation is identity.
const PxVec3 tmp = PxVec3(nIn.x / meshScale.scale.x, nIn.y / meshScale.scale.y, nIn.z / meshScale.scale.z);
const PxReal denom = 1.0f / tmp.magnitude();
return tmp * denom;
}
else
{
const PxMat33 rot(meshScale.rotation);
const PxMat33 diagonal = PxMat33::createDiagonal(meshScale.scale);
const PxMat33 vertex2Shape = (rot.getTranspose() * diagonal) * rot;
const PxMat33 shape2Vertex = vertex2Shape.getInverse();
const PxVec3 tmp = shape2Vertex.transformTranspose(nIn);
const PxReal denom = 1.0f / tmp.magnitude();
return tmp * denom;
}
}
PxU32 physx::PxFindFaceIndex(const PxConvexMeshGeometry& convexGeom, const PxTransform& pose,
const PxVec3& impactPos, const PxVec3& unitDir)
{
PX_ASSERT(unitDir.isFinite());
PX_ASSERT(unitDir.isNormalized());
PX_ASSERT(impactPos.isFinite());
PX_ASSERT(pose.isFinite());
const PxVec3 impact = impactPos - unitDir * gEpsilon;
const PxVec3 localPoint = pose.transformInv(impact);
const PxVec3 localDir = pose.rotateInv(unitDir);
// Create shape to vertex scale transformation matrix
const PxMeshScale& meshScale = convexGeom.scale;
const PxMat33 rot(meshScale.rotation);
PxMat33 shape2VertexSkew = rot.getTranspose();
const PxMat33 diagonal = PxMat33::createDiagonal(PxVec3(1.0f / meshScale.scale.x, 1.0f / meshScale.scale.y, 1.0f / meshScale.scale.z));
shape2VertexSkew = shape2VertexSkew * diagonal;
shape2VertexSkew = shape2VertexSkew * rot;
const PxU32 nbPolys = convexGeom.convexMesh->getNbPolygons();
PxU32 minIndex = 0;
PxReal minD = PX_MAX_REAL;
for (PxU32 j = 0; j < nbPolys; j++)
{
PxHullPolygon hullPolygon;
convexGeom.convexMesh->getPolygonData(j, hullPolygon);
// transform hull plane into shape space
PxPlane plane;
const PxVec3 tmp = shape2VertexSkew.transformTranspose(PxVec3(hullPolygon.mPlane[0],hullPolygon.mPlane[1],hullPolygon.mPlane[2]));
const PxReal denom = 1.0f / tmp.magnitude();
plane.n = tmp * denom;
plane.d = hullPolygon.mPlane[3] * denom;
PxReal d = plane.distance(localPoint);
if (d < 0.0f)
continue;
const PxReal tweak = plane.n.dot(localDir) * gEpsilon;
d += tweak;
if (d < minD)
{
minIndex = j;
minD = d;
}
}
return minIndex;
}