My model has a clear plastic (or glass) dome with objects inside. The objects appear dark. I've tried the glass shader with color 100% RGB, with very small IOR, and using just a refraction shader.
I know Cycles has problems with caustics, but I just want broad illumination to fall clean through the glass. The light-to-column path can ignore refraction, but is blocked or tremendously attenuated. The camera-column path needs refraction, and seems to work fine anyway.
This demo image offers all optical paths of interest:
- light upon object, seen directly
- light upon object, seen through glass (looks okay)
- light through glass onto object, seen directly. This is the shadow on the lit side of the column just below the glass tubing. I expect full illumination, but there is shadow. There is some light, but it's diffuse light from the floor.
- light through glass onto object, seen through glass. This
I did at one point try non-progressive rendering, and find extremely coarse light where there shouldn't be shadow, but this is not a practical way to make nice images. I've even tried cranking up certain sampling settings to many thousands, but still get bad noise though less, at the cost of long render times. I would like to finish my creations sometime before "Star Trek, the Generation After the Next" becomes real life, if you know what I mean. The next image is an example. I think Transmission in Sampling was 5000, but not sure.
I'm using Cycles in Blender 2.67 on a quad core Linux machine, 16GB RAM. Machine limits have never been a problem for 3D rendering.
Possibly, I screwed up some setting when I made my startup file, and just need to fix it. OTOH maybe this is just a limitation of path tracing, or of the way Cycles does it. If that's the case, what to real-world Blender artists do when they need to produce images on a budget and schedule? What is the practical real-world fix?