I’m simulating a box made of translucent fabric, light a photo light box… I haven’t figured out how to get this to work. I can -see- the light where it’s hitting the material, but it doesn’t seem to be actually distributing any inside the box. I’ve tried flipping normals.
In this model, there’s a single spotlight above. No ambient light, world color is black.
However… the outside is lighting up
Should work if you just mix diffuse and translucency shader (then fresnel mix in glossy if desired). Actual translucency don’t rely on caustics, and subsurface scattering don’t transport light at all. I use this setup for thin geometry based curtains all the time.
It is prone to producing noise simply for being indirect, so fake it with emission if you can, i.e. baking it in.