#define EPSILON 0.000001
#define CROSS(dest,v1,v2); \
dest[0]=v1[1]*v2[2]-v1[2]*v2[1]; \
dest[1]=v1[2]*v2[0]-v1[0]*v2[2]; \
dest[2]=v1[0]*v2[1]-v1[1]*v2[0];
#define DOT(v1,v2) ( v1[0]*v2[0]+v1[1]*v2[1]+v1[2]*v2[2])
#define SUB(dest,v1,v2) \
dest[0]=v1[0]-v2[0]; \
dest[1]=v1[1]-v2[1]; \
dest[2]=v1[2]-v2[2];
int intersect_triangle(double orig[3], double dir[3], double vert0[3], double vert1[3], double vert2[3], double *t, double *u, double *v);
int main() {
double origin[3] = {1.0,2.0,3.0};
double direction[3] = {0.0,0.0,1.0};
double vertex0[3] = {1.0,2.0,3.0};
double vertex1[3] = {4.0,5.0,6.0};
double vertex2[3] = {7.0,8.0,9.0};
double t = 1.0;
double* tptr;
tptr = &t;
double u = 2.0; double* uptr; uptr=&u;
double v = 3.0; double* vptr; vptr=&v;
cout << intersect_triangle( origin, direction, vertex0, vertex1, vertex2, tptr, uptr, vptr);
return 0;
}
int intersect_triangle(double orig[3], double dir[3], double vert0[3], double vert1[3], double vert2[3], double *t, double *u, double *v)
{
double edge1[3], edge2[3], tvec[3], pvec[3], qvec[3];
double det, inv_det;
// find vectors for two edges sharing vert0
SUB(edge1, vert1, vert0);
SUB(edge2, vert2, vert0);
// begin calculation determinant - also used to calculate U parameter
CROSS(pvec, dir, edge2);
// if determinant is near zero, ray lies in plane of triangle
det = DOT(edge1, pvec);
if (det < EPSILON)
return 0;
// calculate distance from vert0 to ray origin
SUB(tvec, orig, vert0);
// calculate U parameter and test bounds
*u = DOT(tvec, pvec);
if (*u < 0.0 || *u > det)
return 0;
// prepare to test V parameter
CROSS(qvec, tvec, edge1);
// calculate V parameter and test bounds
*v = DOT(dir, qvec);
if (*v < 0.0 || *u + *v > det)
return 0;
// calculate t, scale parameters, ray intersects triangle
*t = DOT(edge2, qvec);
inv_det = 1.0 / det;
*t *= inv_det;
*u *= inv_det;
*v *= inv_det;
return 1;
}