Currently I am fighting with lighting artefacts within a smoke simulation, when the lightsource is within the volume and especially also within a transparent object within this volume. (Note this question is about the old Blender Internal engine, not Cycles).
Basically I can show the problems with a simple demo setup:
- A ground plane which receives shadows from transparent objects;
- A container (cube) with a volume material, here a simple, constant density;
- A small cube which is transparent so the light can pass out. This small cube is located within the container;
- A simple point light within the small cube and thus also within the container and the voumetric material.
This will give you a situation like the following:
Note the following problems:
- The floor within the volume is way brighter than outside, as if the volume material has a semi-transparent bounding;
- The volume material does not interact properly with the light source (without encasing the light within the small transparent box, it would show up as lit);
- The volume also does not cast proper shadows onto the surrounding plane.
Is this a known problem (with Blender Internal)? Is there anything I can configure differently to make it work?
I could not find any option to make the volume material receive transparent shadows; on regular solid shading material, there is such an option ("Receive Transparent" in the shadow pane).
This problem is especially anoying with the smoke simulation, since there the adaptive domain object takes on the role of the volume container, thus creating a dancing bright patch on the ground as soon as some light source moves into the smoke domain.
The only workaround I see right now would be to use light groups and basically clone several copies of the light source...