// CCW means that in this example we must swap p1 and p2
void Layer::create_segments() {
int skipped = 0, no_intersect=0;
for(linkedlistnode *it = candidates->first; it != NULL; it = it->next ) {
stl_face *f = (stl_face*) it->payload;
line *l = intersection_line(f, this->height);
if (l == 0) {
no_intersect++;
continue;
}
// the vector from p1 to p2
const point p1p2 = {l->p2.x - l->p1.x, l->p2.y - l->p1.y};
// should to short segments be skipped?, yes
if (std::abs(p1p2.x * p1p2.x + p1p2.y * p1p2.y) < EPSILON * EPSILON) {
skipped++;
continue;
}
assert(std::abs(p1p2.x * p1p2.x + p1p2.y * p1p2.y) > EPSILON*EPSILON);
// project onto zx plane, and well call z for y
const point normal = {f->normal.x, f->normal.z};
assert(std::abs(normal.x * normal.x + normal.y * normal.y) > EPSILON*EPSILON);
// we can calculate this as z = 0;
float cross = p1p2.x*normal.y - p1p2.y * normal.x;
// change the order so we are sure that p1 is the first point in a CCW polygon
if (cross < 0) {
/* swap p1 and p2 */
point tmp = l->p1;
l->p1 = l->p2;
l->p2 = tmp;
}
segments->push_back(l);
}
printf("skipping %d short segments and %d none intersecting \n", skipped, no_intersect);
}
//static
// returns 'true' if planes intersect, and stores the result
// the second and third arguments are treated as planes
// where mPoint is on the plane and mDirection is the normal
// result.mPoint will be the intersection line's closest approach
// to first_plane.mPoint
bool LLLine::getIntersectionBetweenTwoPlanes( LLLine& result, const LLLine& first_plane, const LLLine& second_plane )
{
// TODO -- if we ever get some generic matrix solving code in our libs
// then we should just use that, since this problem is really just
// linear algebra.
F32 dot = fabs(first_plane.mDirection * second_plane.mDirection);
if (dot > ALMOST_PARALLEL)
{
// the planes are nearly parallel
return false;
}
LLVector3 direction = first_plane.mDirection % second_plane.mDirection;
direction.normalize();
LLVector3 first_intersection;
{
LLLine intersection_line(first_plane);
intersection_line.mDirection = direction % first_plane.mDirection;
intersection_line.mDirection.normalize();
intersection_line.intersectsPlane(first_intersection, second_plane);
}
/*
LLVector3 second_intersection;
{
LLLine intersection_line(second_plane);
intersection_line.mDirection = direction % second_plane.mDirection;
intersection_line.mDirection.normalize();
intersection_line.intersectsPlane(second_intersection, first_plane);
}
*/
result.mPoint = first_intersection;
result.mDirection = direction;
return true;
}
