lighting_freak wrote: ↑Wed Jul 03, 2019 7:56 am
I have a scene that represents a common lighting scenario.
A row of LED illuminates a volume diffuse, but mostly polished, lens.
All this is built in a housing and closed by a clear cover lens.
Do you believe I'm doing something wrong, or is CPU only not dead yet?
I guess it's an SDS-path issue.
Remember, BiDir can render SDS-paths with mesh lights like in your scene, albeit slowly.
But light tracing cannot.
Light tracing works like this:
A ray originates from a light source, hitting some object in the scene.
If it is a specular surface, the ray will be reflected (or split and refracted too) according to optical laws and continue until it hits another surface.
If it is a diffuse surface, a test will be made if the camera is in line of sight and if so, the shading colour of the surface will be transmitted to the corresponding pixel.
This means that light tracing can only connect to the camera if the last hitpoint was a diffuse surface, all specular surfaces will appear black because the light rays from there have to follow optical laws and will never hit the camera which is an infinitesimal point.
In your scene a clear glass covers the whole front of the device and shuts off all light rays to the camera.
Edit: I guess scattering volumes work like diffuse surfaces too.