11_multi_custom_intersection.md

11_multi_custom_intersection

There is not much to say about this demo as custom intersection is already detailed in this other demo.

One difference compared to the previous demo is that we use 2 custom functions:

  std::vector<hiprtFuncNameSet> funcNameSets( GeomTypesCount );
  funcNameSets[SphereTypeIndex].intersectFuncName = "intersectSphere";
  funcNameSets[CircleTypeIndex].intersectFuncName = "intersectCircle";

we use the same intersectSphere than in the previous demo, but we also introduce this new intersectCircle custom intersection:

  // check if there is a hit before ray.maxT. if there is, set it to tOut. hiprt will overwrite ray.maxT after this function
  __device__ bool intersectCircle( const hiprtRay& ray, const void* data, void* payload, hiprtHit& hit )
  {
    const float4* o = reinterpret_cast<const float4*>( data );
    float2		  c = make_float2( o[hit.primID].x, o[hit.primID].y );
    const float	  r = o[hit.primID].w;

    c.x			 = c.x - ray.origin.x;
    c.y			 = c.y - ray.origin.y;
    float d		 = sqrtf( c.x * c.x + c.y * c.y );
    bool  hasHit = d < r;
    if ( !hasHit ) return false;

    hit.normal = normalize( make_float3( d, d, d ) );

    return true;
  }

Note that we now have 2 geomType:

  constexpr uint32_t SphereTypeIndex = 0;
  constexpr uint32_t CircleTypeIndex = 1;

Another difference is that in this demo, we use a hiprtScene, so in the kernel, we have to use hiprtSceneTraversalClosest instead of hiprtGeomCustomTraversalClosest, as explained in the demo introducing the hiprtScene.