Method getIntersectPoint

core/3d/Terrain.cpp:1737–1792

Please refer to 3D Math Primer for Graphics and Game Development

// Please refer to 3D Math Primer for Graphics and Game Development
bool Terrain::Triangle::getIntersectPoint(const Ray& ray, Vec3& intersectPoint) const
{
    // E1
    Vec3 E1 = _p2 - _p1;

    // E2
    Vec3 E2 = _p3 - _p1;

    // P
    Vec3 P;
    Vec3::cross(ray._direction, E2, &P);

    // determinant
    float det = E1.dot(P);

    // keep det > 0, modify T accordingly
    Vec3 T;
    if (det > 0)
    {
        T = ray._origin - _p1;
    }
    else
    {
        T   = _p1 - ray._origin;
        det = -det;
    }

    // If determinant is near zero, ray lies in plane of triangle
    if (det < 0.0001f)
        return false;

    float t;     // ray dist
    float u, v;  // barycentric coordinate
    // Calculate u and make sure u <= 1
    u = T.dot(P);
    if (u < 0.0f || u > det)
        return false;

    // Q
    Vec3 Q;
    Vec3::cross(T, E1, &Q);

    // Calculate v and make sure u + v <= 1
    v = ray._direction.dot(Q);
    if (v < 0.0f || u + v > det)
        return false;

    // Calculate t, scale parameters, ray intersects triangle
    t = E2.dot(Q);

    float fInvDet = 1.0f / det;
    t *= fInvDet;

    intersectPoint = ray._origin + ray._direction * t;
    return true;
}

void Terrain::onBeforeDraw()