Just thought I’d show a frame that I will be rendering a water simulation from, it took me awhile to get it rendering properly.
Cycles sadly doesn’t work for the Caustics, I couldn’t get Yafaray to work nicely either. LuxRender’s Bi-DIr + MLT was unable to handle the scene either!
I ended up using SPPM via LuxRender, and it took about 2 hours for this frame (I will be using post-pro to reduce render time to 1 hour) I also had a few issues with Mitsuba exporter to get this working (so I don’t know what integrator would work best from it)
So here it is, with the difficult part being seeing the caustics underneath the water when the camera is above (Bi-Dir cannot handle such paths properly) Ill be back in about 10 days with an animation
Bi-Dir cannot handle such paths properly
Not bi-dir, only implementations w/o support of camera aperture hit or infinite small light source. Cycles can render anything that lit with mesh light, only time is problem if emission mesh area too small.
I had a similar scene I was unsure about, so I asked on the Lux forum, and they said it was the Specular > Diffuse > Secular that was difficult. In this case its Sun > Glass (refraction) > Matte > Glass (refraction) > Camera and that fails, but the Sun > Glass (reflection) > Matte > Camera works. SPecifically, the caustics on the wall work in Bi-Dir, but the ones udner the water did not render properly.
I’ve heard before that to properly lighten areas within or inside objects with a glass material in Luxrender you have to set it as architectural glass, unfortunately when you do that the water material will lose its refraction.
At least in Cycles you might be able to get something out of it by using lightpath tricks and a physical source to act as the sun (either through a meshlight or through a node setup that builds it into the environment), something where it’s even possible to keep the refractions.
Well… if there is a faster way to render what I’m doing (Without using V-ray or any commercial renderer) that would be good Ill try mess around with Cycles again with a mesh lamp? Sadly I have a 7970 in my desktop, and a 540M in my laptop (which is ~50% faster than my desktop)
Also, being able to use border render in camera view is amazing for testing a small amount of pixels to show materials at a high pass count
Umm Cycles can use Multi GPU’s (nVidia obviously) but I don’t think its via SLI, each card works independantly and needs its own copy of the scene/textures in memory. The tiled rendering allowes each GPU to work on a different tile.
I would be using LuxRenders network rendering, however I had to put the rendering on hold as I upgraded my laptop + desktop to Win 8 and forgot to save the fluid cache I might also wait for a hybrid bi-dir + VCM in SLG3 to see how that works, althogh its not released yet. (Uses best of BiDir + SPPM)
For most tight caustics (small lights + smooth surfaces) any Path Tracer is severely limited, and the only way it can render such caustics is brute forcing its way through them. A Bi-Directional PAth Tracer (LuxRender, Mitsuba, Indigo…) or Photon Mapper (or SPPM) (Lux, Yafaray others?) are alot better at caustics like that.
Quite limited yes, but those that do appear would not be any less physically correct I think (unless you want dispersion/rainbow effect, you would need something like LuxRender for that) I have rendered a caustic scene in LuxRender (Bi-Dir) and SmallLuxGPU (Path tracer) with comparable results, Ill do it again and show it
Ill try mess around with Cycles again with a mesh lamp? Sadly I have a 7970 in my desktop, and a 540M in my laptop (which is ~50% faster than my desktop)
to see how that works 
I might also wait for a hybrid bi-dir + VCM in SLG3 to see how that works, althogh its not released yet. (Uses best of BiDir + SPPM)