source: code/branches/ode/ode-0.9/OPCODE/OPC_RayTriOverlap.h @ 237

#define LOCAL_EPSILON 0.000001f

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/**
 *      Computes a ray-triangle intersection test.
 *      Original code from Tomas Möller's "Fast Minimum Storage Ray-Triangle Intersection".
 *      It's been optimized a bit with integer code, and modified to return a non-intersection if distance from
 *      ray origin to triangle is negative.
 *
 *      \param          vert0   [in] triangle vertex
 *      \param          vert1   [in] triangle vertex
 *      \param          vert2   [in] triangle vertex
 *      \return         true on overlap. mStabbedFace is filled with relevant info.
 */
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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(IS_NEGATIVE_FLOAT(mStabbedFace.mU) || 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(IS_NEGATIVE_FLOAT(mStabbedFace.mV) || 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(IS_NEGATIVE_FLOAT(mStabbedFace.mDistance))                                                           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(IS_NEGATIVE_FLOAT(mStabbedFace.mU) || IR(mStabbedFace.mU)>IEEE_1_0)          return FALSE;

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

                // Calculate V parameter and test bounds
                mStabbedFace.mV = (mDir|qvec) * OneOverDet;
                if(IS_NEGATIVE_FLOAT(mStabbedFace.mV) || 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(IS_NEGATIVE_FLOAT(mStabbedFace.mDistance))                                                           return FALSE;
        }
        return TRUE;
}