// Returns true iff the mesh contains two index defined traingles that intersect.
bool check_triangle_intersections(ofMesh &mesh)
{
int len = mesh.getNumIndices();
for(int i = 0; i < len; i += 3)
{
ofVec3f v1 = mesh.getVertex(mesh.getIndex(i));
ofVec3f v2 = mesh.getVertex(mesh.getIndex(i + 1));
ofVec3f v3 = mesh.getVertex(mesh.getIndex(i + 2));
for(int j = 0; j < len; j += 3)
{
ofVec3f p1 = mesh.getVertex(mesh.getIndex(j));
ofVec3f p2 = mesh.getVertex(mesh.getIndex(j + 1));
ofVec3f p3 = mesh.getVertex(mesh.getIndex(j + 2));
int b = Intersecting(p1, p2, v1, v2, v3);
int b2 = Intersecting(p2, p3, v1, v2, v3);
int b3 = Intersecting(p3, p1, v1, v2, v3);
if(b == 1 || b2 == 1 || b3 == 1)
{
return true;
}
if(point_triangle_intersection(v1, v2, v3, p1)||
point_triangle_intersection(v1, v2, v3, p2)||
point_triangle_intersection(v1, v2, v3, p3))
{
return true;
}
}
}
return false;
}
long t_c_intersection(Triangle3 t)
{
long v1_test,v2_test,v3_test;
float d,denom;
Point3 vect12,vect13,norm;
Point3 hitpp,hitpn,hitnp,hitnn;
/* First compare all three vertexes with all six face-planes */
/* If any vertex is inside the cube, return immediately! */
if ((v1_test = face_plane(t.v1)) == INSIDE) return(INSIDE);
if ((v2_test = face_plane(t.v2)) == INSIDE) return(INSIDE);
if ((v3_test = face_plane(t.v3)) == INSIDE) return(INSIDE);
/* If all three vertexes were outside of one or more face-planes, */
/* return immediately with a trivial rejection! */
if ((v1_test & v2_test & v3_test) != 0) return(OUTSIDE);
/* Now do the same trivial rejection test for the 12 edge planes */
v1_test |= bevel_2d(t.v1) << 8;
v2_test |= bevel_2d(t.v2) << 8;
v3_test |= bevel_2d(t.v3) << 8;
if ((v1_test & v2_test & v3_test) != 0) return(OUTSIDE);
/* Now do the same trivial rejection test for the 8 corner planes */
v1_test |= bevel_3d(t.v1) << 24;
v2_test |= bevel_3d(t.v2) << 24;
v3_test |= bevel_3d(t.v3) << 24;
if ((v1_test & v2_test & v3_test) != 0) return(OUTSIDE);
/* If vertex 1 and 2, as a pair, cannot be trivially rejected */
/* by the above tests, then see if the v1-->v2 triangle edge */
/* intersects the cube. Do the same for v1-->v3 and v2-->v3. */
/* Pass to the intersection algorithm the "OR" of the outcode */
/* bits, so that only those cube faces which are spanned by */
/* each triangle edge need be tested. */
if ((v1_test & v2_test) == 0)
if (check_line(t.v1,t.v2,v1_test|v2_test) == INSIDE) return(INSIDE);
if ((v1_test & v3_test) == 0)
if (check_line(t.v1,t.v3,v1_test|v3_test) == INSIDE) return(INSIDE);
if ((v2_test & v3_test) == 0)
if (check_line(t.v2,t.v3,v2_test|v3_test) == INSIDE) return(INSIDE);
/* By now, we know that the triangle is not off to any side, */
/* and that its sides do not penetrate the cube. We must now */
/* test for the cube intersecting the interior of the triangle. */
/* We do this by looking for intersections between the cube */
/* diagonals and the triangle...first finding the intersection */
/* of the four diagonals with the plane of the triangle, and */
/* then if that intersection is inside the cube, pursuing */
/* whether the intersection point is inside the triangle itself. */
/* To find plane of the triangle, first perform crossproduct on */
/* two triangle side vectors to compute the normal vector. */
SUB(t.v1,t.v2,vect12);
SUB(t.v1,t.v3,vect13);
CROSS(vect12,vect13,norm)
/* The normal vector "norm" X,Y,Z components are the coefficients */
/* of the triangles AX + BY + CZ + D = 0 plane equation. If we */
/* solve the plane equation for X=Y=Z (a diagonal), we get */
/* -D/(A+B+C) as a metric of the distance from cube center to the */
/* diagonal/plane intersection. If this is between -0.5 and 0.5, */
/* the intersection is inside the cube. If so, we continue by */
/* doing a point/triangle intersection. */
/* Do this for all four diagonals. */
d = norm.x * t.v1.x + norm.y * t.v1.y + norm.z * t.v1.z;
/* if one of the diagonals is parallel to the plane, the other will intersect the plane */
if(fabs(denom=(norm.x + norm.y + norm.z))>EPS)
/* skip parallel diagonals to the plane; division by 0 can occur */
{
hitpp.x = hitpp.y = hitpp.z = d / denom;
if (fabs(hitpp.x) <= 0.5)
if (point_triangle_intersection(hitpp,t) == INSIDE) return(INSIDE);
}
if(fabs(denom=(norm.x + norm.y - norm.z))>EPS)
{
hitpn.z = -(hitpn.x = hitpn.y = d / denom);
if (fabs(hitpn.x) <= 0.5)
if (point_triangle_intersection(hitpn,t) == INSIDE) return(INSIDE);
}
if(fabs(denom=(norm.x - norm.y + norm.z))>EPS)
{
hitnp.y = -(hitnp.x = hitnp.z = d / denom);
if (fabs(hitnp.x) <= 0.5)
if (point_triangle_intersection(hitnp,t) == INSIDE) return(INSIDE);
}
if(fabs(denom=(norm.x - norm.y - norm.z))>EPS)
{
hitnn.y = hitnn.z = -(hitnn.x = d / denom);
if (fabs(hitnn.x) <= 0.5)
if (point_triangle_intersection(hitnn,t) == INSIDE) return(INSIDE);
}
/* No edge touched the cube; no cube diagonal touched the triangle. */
/* We're done...there was no intersection. */
return(OUTSIDE);
}
