Function rayTriangleIntersect

source/MRMesh/MRTriangleIntersection.h:365–404

template <typename T>
std::optional<TriIntersectResult> rayTriangleIntersect( const Vector3<T>& oriA, const Vector3<T>& oriB, const Vector3<T>& oriC,
    const IntersectionPrecomputes<T>& prec )
{
    const T& Sx = prec.Sx;
    const T& Sy = prec.Sy;
    const T& Sz = prec.Sz;

    const T Ax = oriA[prec.idxX] - Sx * oriA[prec.maxDimIdxZ];
    const T Ay = oriA[prec.idxY] - Sy * oriA[prec.maxDimIdxZ];
    const T Bx = oriB[prec.idxX] - Sx * oriB[prec.maxDimIdxZ];
    const T By = oriB[prec.idxY] - Sy * oriB[prec.maxDimIdxZ];
    const T Cx = oriC[prec.idxX] - Sx * oriC[prec.maxDimIdxZ];
    const T Cy = oriC[prec.idxY] - Sy * oriC[prec.maxDimIdxZ];

    // due to fused multiply-add (FMA): (A*B-A*B) can be different from zero, so we need epsilon
    const T eps = std::numeric_limits<T>::epsilon() * std::max( { Ax, Bx, Cx, Ay, By, Cy } );
    T U = Cx * By - Cy * Bx;
    T V = Ax * Cy - Ay * Cx;
    T W = Bx * Ay - By * Ax;

    if( U < -eps || V < -eps || W < -eps )
    {
        if( U > eps || V > eps || W > eps )
        {
            // U,V,W have clearly different signs, so the ray misses the triangle
            return std::nullopt;
        }
    }

    T det = U + V + W;
    if( det == T( 0 ) )
        return std::nullopt;
    const T Az = Sz * oriA[prec.maxDimIdxZ];
    const T Bz = Sz * oriB[prec.maxDimIdxZ];
    const T Cz = Sz * oriC[prec.maxDimIdxZ];
    const T t = U * Az + V * Bz + W * Cz;

    auto invDet = T( 1 ) / det;
    return TriIntersectResult( float( V * invDet ), float( W * invDet ), float( t * invDet ) );
}

MR_BIND_TEMPLATE( std::optional<TriIntersectResult> rayTriangleIntersect( const Vector3<float >& oriA, const Vector3<float >& oriB, const Vector3<float >& oriC, const IntersectionPrecomputes<float >& prec ) )
MR_BIND_TEMPLATE( std::optional<TriIntersectResult> rayTriangleIntersect( const Vector3<double>& oriA, const Vector3<double>& oriB, const Vector3<double>& oriC, const IntersectionPrecomputes<double>& prec ) )