Sorry For making 3 consecutive posts. No spamming intended. The edit time limit for my previous post has expired.

A clarification regarding Embree:

Embree is not a full-blown renderer like Lux or Octane which need their own shading or lighting systems. Embree is a set of fast raytracing routines to be incorporated into a renderer, to replace the renderer's slower raytracing code, the rest of the renderer remaining unchanged.

It's like a heart transplant. You take the ailing heart out and replace it with a new healthy heart, the rest of the body remains unchanged.

Implementing Embree inside a renderer is not a trivial task, but it is not a multi-year project with huge resource requirements.

Intel has done it very intelligently, i.e. give 3D app developers a set of super-fast raytracing routines whose implementation should have minimal impact on the rest of the renderer.

At least this is my understabding of how Embree works.