Mirror Reflections

I just realised that mirrors in blender do not actually reflect light beams properly.

I set up a spot light with a tight beam directed on a completely reflective surface. I enclosed the whole thing in a cube with a volume scatter material to show the actual beam, and what I found is that you can see the ray from the source to the mirror, but after that it disappears… There is no actual reflected beam from the mirror onwards.

Am I doing something wrong or is this just something blender doesn’t do?


Go to the Properties panel > Rendering tab > Light Paths section, and make sure none of these sliders is set to 0. The sliders under the “Bounces” heading determine the number of times light beams bounce. Maybe your Volume slider is set to 0, which is why you’re getting zero bounces in your volume cube.

If tweaking these values fixes your volume bounce problem, does it also fix your mirror reflection problem, or is that a totally separate issue?

As far as I know, only spectral renderers are able to do this. You’re shooting a direct light source at a mirror through the volume and then hoping an indirect bounce will then travel back through. I don’t think Cycles can do this. Luxrender might be able to though.

I misspoke, actually using a simple forward path tracer like Cycles won’t get you what you want even after hours of sampling, but renderers that use Metropolis Light Transport can, which is one of the methods (primary) used by LuxRender. It’s a bit technical for me to explain here, but you can search for Metropolis Light Transport, or check out LuxRender at http://www.luxrender.net/en_GB/index There’s a wealth of information out there.

can you upload sample to test it

happy cl