GuIntersectionCapsuleTriangle.h

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#ifndef GU_INTERSECTION_CAPSULE_TRIANGLE_H
#define GU_INTERSECTION_CAPSULE_TRIANGLE_H
 
#include "GuCapsule.h"
#include "foundation/PxUtilities.h"
 
namespace physx
{
namespace Gu
{
    // PT: precomputed data for capsule-triangle test. Useful when testing the same capsule vs several triangles.
    struct CapsuleTriangleOverlapData
    {
        PxVec3      mCapsuleDir;
        float       mBDotB;
        float       mOneOverBDotB;
 
        void        init(const Capsule& capsule)
        {
            const PxVec3 dir = capsule.p1 - capsule.p0;
            const float BDotB = dir.dot(dir);
            mCapsuleDir     = dir;
            mBDotB          = BDotB;
            mOneOverBDotB   = BDotB!=0.0f ? 1.0f/BDotB : 0.0f;
        }
    };
 
    // PT: tests if projections of capsule & triangle overlap on given axis
    PX_FORCE_INLINE PxU32 testAxis(const PxVec3& p0, const PxVec3& p1, const PxVec3& p2, const Capsule& capsule, const PxVec3& axis)
    {
        // Project capsule
        float min0 = capsule.p0.dot(axis);
        float max0 = capsule.p1.dot(axis);
        if(min0>max0)
            PxSwap(min0, max0);
        const float MR = axis.magnitude()*capsule.radius;
        min0 -= MR;
        max0 += MR;
 
        // Project triangle
        float min1, max1;
        {
            min1 = max1 = p0.dot(axis);
            float dp = p1.dot(axis);
            if(dp<min1) min1 = dp;
            if(dp>max1) max1 = dp;
            dp = p2.dot(axis);
            if(dp<min1) min1 = dp;
            if(dp>max1) max1 = dp;
        }
 
        // Test projections
        if(max0<min1 || max1<min0)
            return 0;
 
        return 1;
    }
 
    // PT: computes shortest vector going from capsule axis to triangle edge
    PX_FORCE_INLINE PxVec3 computeEdgeAxis( const PxVec3& p, const PxVec3& a,
                                            const PxVec3& q, const PxVec3& b,
                                            float BDotB, float oneOverBDotB)    
    {
        const PxVec3 T = q - p;
        const float ADotA = a.dot(a);
        const float ADotB = a.dot(b);
        const float ADotT = a.dot(T);
        const float BDotT = b.dot(T);
 
        const float denom = ADotA*BDotB - ADotB*ADotB;
 
        float t = denom!=0.0f ? (ADotT*BDotB - BDotT*ADotB) / denom : 0.0f;
        t = PxClamp(t, 0.0f, 1.0f);
 
        float u = (t*ADotB - BDotT) * oneOverBDotB;
 
        if(u<0.0f)
        {
            u = 0.0f;
            t = ADotT / ADotA;
            t = PxClamp(t, 0.0f, 1.0f);
        }
        else if(u>1.0f)
        {
            u = 1.0f;
            t = (ADotB + ADotT) / ADotA;
            t = PxClamp(t, 0.0f, 1.0f);
        }
        return T + b*u - a*t;
    }
 
    bool intersectCapsuleTriangle(const PxVec3& normal, const PxVec3& p0, const PxVec3& p1, const PxVec3& p2, const Gu::Capsule& capsule, const CapsuleTriangleOverlapData& params);
}
}
 
#endif