Furnace test

A test to catch any bugs or issues with energy conservation

Make a gigantic sphere, apply an incandescent material to it. Make it have a weight of 1.0 and a 50% gray color. Make sure you disable secondary GI, you only want 1 bounce of GI. Then make a smaller sphere and this is your “probe” sphere you check. Adding your material to it with 1.0 white albedo. Then check each lobe individually like say turn on Oren-nayar and set the diffuse roughness to 1.0 with zero specular weight

If it gets brighter or darker that means your gaining or losing energy. Ideally you want to be as close as the background, to be invisible basically

so if you color pick the sphere and fresnel etc it should be within 0-3% or so of the same value as the background. ideally 100% match.

so you end up with something like this, this is Arnold and RS, you can slightly see the sphere, and thats because there is a tiny loss of energy around ~2% depending on where you click vs the 50% gray background. (RAW Values)