I want to implement refraction using embree. I put a standard cube ( 12 triangles , 8 vertices) like in triangle tutorial embree 3.2. The problem is that primary ray hits first face of cube but not the second (it passes through the cube ). I have no idea why. Is there some flag to turn on to trace transparent objects? I tried rtcSetSceneFlags(scene, RTC_SCENE_FLAG_ROBUST); but it doesn't change a thing.Help pls!