作业3中的inTriangle问题

[tmk]

作业3的OBJ_Loader.h中inTriangle方法为什么是判断点在叉积上的投影，而不是判断点减去另一个三角形顶点（得到一个在三角形平面上的向量）叉积上的投影？

// Check to see if a Vector3 Point is within a 3 Vector3 Triangle
        bool inTriangle(Vector3 point, Vector3 tri1, Vector3 tri2, Vector3 tri3)
        {
            // Test to see if it is within an infinite prism that the triangle outlines.
            bool within_tri_prisim = SameSide(point, tri1, tri2, tri3) && SameSide(point, tri2, tri1, tri3)
                                     && SameSide(point, tri3, tri1, tri2);

            // If it isn't it will never be on the triangle
            if (!within_tri_prisim)
                return false;

            // Calulate Triangle's Normal
            Vector3 n = GenTriNormal(tri1, tri2, tri3);

            // Project the point onto this normal
           <strong> Vector3 proj = math::ProjV3(point, n);</strong>

            // If the distance from the triangle to the point is 0
            //	it lies on the triangle
            if (math::MagnitudeV3(proj) == 0)
                return true;
            else
                return false;
        }

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