User defined geometry bouding box overlapping

Jianbo_Q_ — Wed, 13 Dec 2017 12:37:26 GMT

Hello,

I meet a problem when defining the user defined geometry. I simply defined a box, i.e. its bouding box is the same as the box itself.

I implemented the intersection function as following:

The problem is when I put two boxes up and down with one common face, i.e. they are aligned perfectly.

For example, the center of the two boxes are: (0,0,0), (0, 10,0). while the edge length of them is 10.

When I shoot a ray from top: org (0, 100, 0), dir (0, -1, 0). The 'cellIntersectFunc' function will be called two times:

intersect 0
intersect 0
p: (0, 5, 0)
p1: (0, 5, 0)

The two intersected points (tnear and tfar) is the same, which is the common edge of the two boxes.

If I seperate them slighly. (0,0,0), (0, 10.001,0), The results is correct:

intersect 0
p: (0, 15.001, 0)
p1: (0, 5.001, 0)

Does anyone know what's wrong with this problem. I don't want any gaps between boxes, because some

rays may just go through this gaps and then produce errors.

Thank you!

void cellIntersectFunc(void* cell_i, RTCRay& ray, size_t item) {
cout << "intersect " << item<< endl;

const Cell* cells = (const Cell*)cell_i;

const Cell& cell = cells[item];

   Vec3fa dRcp = 1/ray.dir;
   Vec3fa upper_right = cell.left_bottom + Vec3fa(cell.xzExtent, cell.yExtent, cell.xzExtent);
for (int i = 0; i < 3; i++) {
       const float origin = ray.org;
       const float minVal = cell.left_bottom, maxVal = upper_right;
if (ray.dir == 0) {//The ray is parallel to the planes.
           if (origin < minVal || origin > maxVal) {
               return;
           }
       }
       else {
           float t1 = (minVal - origin) * dRcp;
           float t2 = (maxVal - origin) * dRcp;
           bool flip = t1 > t2;
           if (flip)
               swap(t1, t2);

           ray.tnear = std::max(t1, ray.tnear);
           ray.tfar = std::min(t2, ray.tfar);
           if (!(ray.tnear <= ray.tfar))
               return;
       }
   }
   ray.geomID = cell.geomID;
   ray.primID = (unsigned int)item;
return;
}

That the intersection

BenthinC_Intel — Thu, 14 Dec 2017 13:56:18 GMT

That the intersection callback is called twice for the same object is very strange. Could you send us a more complete reproducer (including geometry setup) to embree_support@intel.com.

Thanks.

topic That the intersection in Intel® Embree Ray Tracing Kernels

User defined geometry bouding box overlapping

That the intersection