long point_triangle_intersection(Point3 p, Triangle3 t)
{
long sign12,sign23,sign31;
Point3 vect12,vect23,vect31,vect1h,vect2h,vect3h;
Point3 cross12_1p,cross23_2p,cross31_3p;
/* First, a quick bounding-box test: */
/* If P is outside triangle bbox, there cannot be an intersection. */
if (p.x > MAX3(t.v1.x, t.v2.x, t.v3.x)) return(OUTSIDE);
if (p.y > MAX3(t.v1.y, t.v2.y, t.v3.y)) return(OUTSIDE);
if (p.z > MAX3(t.v1.z, t.v2.z, t.v3.z)) return(OUTSIDE);
if (p.x < MIN3(t.v1.x, t.v2.x, t.v3.x)) return(OUTSIDE);
if (p.y < MIN3(t.v1.y, t.v2.y, t.v3.y)) return(OUTSIDE);
if (p.z < MIN3(t.v1.z, t.v2.z, t.v3.z)) return(OUTSIDE);
/* For each triangle side, make a vector out of it by subtracting vertexes; */
/* make another vector from one vertex to point P. */
/* The crossproduct of these two vectors is orthogonal to both and the */
/* signs of its X,Y,Z components indicate whether P was to the inside or */
/* to the outside of this triangle side. */
SUB(t.v1, t.v2, vect12)
SUB(t.v1, p, vect1h);
CROSS(vect12, vect1h, cross12_1p)
sign12 = SIGN3(cross12_1p); /* Extract X,Y,Z signs as 0..7 or 0...63 integer */
SUB(t.v2, t.v3, vect23)
SUB(t.v2, p, vect2h);
CROSS(vect23, vect2h, cross23_2p)
sign23 = SIGN3(cross23_2p);
SUB(t.v3, t.v1, vect31)
SUB(t.v3, p, vect3h);
CROSS(vect31, vect3h, cross31_3p)
sign31 = SIGN3(cross31_3p);
/* If all three crossproduct vectors agree in their component signs, */
/* then the point must be inside all three. */
/* P cannot be OUTSIDE all three sides simultaneously. */
/* this is the old test; with the revised SIGN3() macro, the test
* needs to be revised. */
#ifdef OLD_TEST
if ((sign12 == sign23) && (sign23 == sign31))
return(INSIDE);
else
return(OUTSIDE);
#else
return ((sign12 & sign23 & sign31) == 0) ? OUTSIDE : INSIDE;
#endif
}
///
// PointTriangleIntersection()
//
// Test if 3D point is inside 3D triangle
static
int PointTriangleIntersection(const vector3& p, const TRI& t)
{
int sign12,sign23,sign31;
vector3 vect12,vect23,vect31,vect1h,vect2h,vect3h;
vector3 cross12_1p,cross23_2p,cross31_3p;
///
// First, a quick bounding-box test:
// If P is outside triangle bbox, there cannot be an intersection.
//
if (p.x() > MAX3(t.m_P[0].x(), t.m_P[1].x(), t.m_P[2].x())) return(OUTSIDE);
if (p.y() > MAX3(t.m_P[0].y(), t.m_P[1].y(), t.m_P[2].y())) return(OUTSIDE);
if (p.z() > MAX3(t.m_P[0].z(), t.m_P[1].z(), t.m_P[2].z())) return(OUTSIDE);
if (p.x() < MIN3(t.m_P[0].x(), t.m_P[1].x(), t.m_P[2].x())) return(OUTSIDE);
if (p.y() < MIN3(t.m_P[0].y(), t.m_P[1].y(), t.m_P[2].y())) return(OUTSIDE);
if (p.z() < MIN3(t.m_P[0].z(), t.m_P[1].z(), t.m_P[2].z())) return(OUTSIDE);
///
// For each triangle side, make a vector out of it by subtracting vertexes;
// make another vector from one vertex to point P.
// The crossproduct of these two vectors is orthogonal to both and the
// signs of its X,Y,Z components indicate whether P was to the inside or
// to the outside of this triangle side.
//
SUB(t.m_P[0], t.m_P[1], vect12);
SUB(t.m_P[0], p, vect1h);
CROSS(vect12, vect1h, cross12_1p)
sign12 = SIGN3(cross12_1p); /* Extract X,Y,Z signs as 0..7 or 0...63 integer */
SUB(t.m_P[1], t.m_P[2], vect23)
SUB(t.m_P[1], p, vect2h);
CROSS(vect23, vect2h, cross23_2p)
sign23 = SIGN3(cross23_2p);
SUB(t.m_P[2], t.m_P[0], vect31)
SUB(t.m_P[2], p, vect3h);
CROSS(vect31, vect3h, cross31_3p)
sign31 = SIGN3(cross31_3p);
///
// If all three crossproduct vectors agree in their component signs, /
// then the point must be inside all three.
// P cannot be OUTSIDE all three sides simultaneously.
//
return (((sign12 & sign23 & sign31) == 0) ? OUTSIDE : INSIDE);
}
