Function compute_segment_plane_intersection

source/math.cpp:158–196

Intersect a line segment with a plane Return values: 'p': The segment lies wholly within the plane. 'q': The(first) q endpoint is on the plane (but not 'p'). 'r' : The(second) r endpoint is on the plane (but not 'p'). '0' : The segment lies strictly to one side or the other of the plane. '1': The segment intersects the plane, and none of {p, q, r} hold.

    // '0' : The segment lies strictly to one side or the other of the plane.
    // '1': The segment intersects the plane, and none of {p, q, r} hold.
    char compute_segment_plane_intersection(vec3& p, const vec3& normal, const double& d_coeff,
        const vec3& q, const vec3& r)
    {

        // vec3 planeNormal;
        // double planeDCoeff;
        // planeNormalLargestComponent = compute_polygon_plane_coefficients(planeNormal, planeDCoeff, polygonVertices,
        // polygonVertexCount);

        double num = d_coeff - dot_product(q, normal);
        const vec3 rq = (r - q);
        double denom = dot_product(rq, normal);

        if (denom == double(0.0) /* Segment is parallel to plane.*/) {
            if (num == double(0.0)) { // 'q' is on plane.
                return 'p'; // The segment lies wholly within the plane
            } else {
                return '0';
            }
        }

        double t = num / denom;

        for (int i = 0; i < 3; ++i) {
            p[i] = q[i] + t * (r[i] - q[i]);
        }

        if ((double(0.0) < t) && (t < double(1.0))) {
            return '1'; // The segment intersects the plane, and none of {p, q, r} hold
        } else if (num == double(0.0)) // t==0
        {
            return 'q'; // The (first) q endpoint is on the plane (but not 'p').
        } else if (num == denom) // t==1
        {
            return 'r'; // The (second) r endpoint is on the plane (but not 'p').
        } else {
            return '0'; // The segment lies strictly to one side or the other of the plane
        }
    }

    bool determine_three_noncollinear_vertices(int& i, int& j, int& k, const std::vector<vec3>& polygon_vertices,