OPC_RayTriOverlap.h

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#define LOCAL_EPSILON 0.000001f


inline_ bool RayCollider::RayTriOverlap(const Point& vert0, const Point& vert1, const Point& vert2)
{
    // Stats
    mNbRayPrimTests++;

    // Find vectors for two edges sharing vert0
    Point edge1 = vert1 - vert0;
    Point edge2 = vert2 - vert0;

    // Begin calculating determinant - also used to calculate U parameter
    Point pvec = mDir^edge2;

    // If determinant is near zero, ray lies in plane of triangle
    float det = edge1|pvec;

    if(mCulling)
    {
        if(det<LOCAL_EPSILON)                                                       return FALSE;
        // From here, det is > 0. So we can use integer cmp.

        // Calculate distance from vert0 to ray origin
        Point tvec = mOrigin - vert0;

        // Calculate U parameter and test bounds
        mStabbedFace.mU = tvec|pvec;
//      if(IR(u)&0x80000000 || u>det)                   return FALSE;
        if((mStabbedFace.mU < 0.0f) || IR(mStabbedFace.mU)>IR(det))     return FALSE;

        // Prepare to test V parameter
        Point qvec = tvec^edge1;

        // Calculate V parameter and test bounds
        mStabbedFace.mV = mDir|qvec;
        if((mStabbedFace.mV < 0.0f) || mStabbedFace.mU+mStabbedFace.mV>det) return FALSE;

        // Calculate t, scale parameters, ray intersects triangle
        mStabbedFace.mDistance = edge2|qvec;
        // Det > 0 so we can early exit here
        // Intersection point is valid if distance is positive (else it can just be a face behind the orig point)
        if((mStabbedFace.mDistance < 0.0f))                             return FALSE;
        // Else go on
        float OneOverDet = 1.0f / det;
        mStabbedFace.mDistance *= OneOverDet;
        mStabbedFace.mU *= OneOverDet;
        mStabbedFace.mV *= OneOverDet;
    }
    else
    {
        // the non-culling branch
        if(det>-LOCAL_EPSILON && det<LOCAL_EPSILON)                                 return FALSE;
        float OneOverDet = 1.0f / det;

        // Calculate distance from vert0 to ray origin
        Point tvec = mOrigin - vert0;

        // Calculate U parameter and test bounds
        mStabbedFace.mU = (tvec|pvec) * OneOverDet;
//      if(IR(u)&0x80000000 || u>1.0f)                  return FALSE;
        if((mStabbedFace.mU < 0.0f) || (mStabbedFace.mU>1.0f))      return FALSE;

        // prepare to test V parameter
        Point qvec = tvec^edge1;

        // Calculate V parameter and test bounds
        mStabbedFace.mV = (mDir|qvec) * OneOverDet;
        if((mStabbedFace.mV < 0.0f) || mStabbedFace.mU+mStabbedFace.mV>1.0f)    return FALSE;

        // Calculate t, ray intersects triangle
        mStabbedFace.mDistance = (edge2|qvec) * OneOverDet;
        // Intersection point is valid if distance is positive (else it can just be a face behind the orig point)
        if((mStabbedFace.mDistance < 0.0f))                             return FALSE;
    }
    return TRUE;
}