Importons/Irradiance Particles

For another personal tutorial, I did this tutorial about Importons and Irradiance Particles. Basically, Importons and Irradiance Particles are another form of indirect lighting, like global illumination and final gather, and they work together to create indirect lighting effects that can be high quality and take less time to render. The importons and irradiance particles only look at what the camera sees to render things out, so it doesn't spend a lot of time rendering things that won't be seen. Anyway, here's some pictures.

Here's an image rendered with final gather. You can see it looks pretty good, but it took about 21 minutes to render the image... which is a pretty long time.

And here's the same image rendered with importons and irradiance particles. It looks pretty similar to the final gather picture, but it only took about 8 minutes to render. As you can see, importons and irradiance particles allow you to get very good results with a lot less time. Also, you could probably turn up the render settings to get an even higher quality image. Anyway, I guess it's just good to know multiple techniques for adding indirect lighting to your scene.

Caustics

For a personal tutorial, I did a caustics tutorial here. It wasn't too bad, I just had to mess around with the settings a lot to get some results. I'm still having some problems with the caustics doing weird things and I'm trying to figure out why, but here's what I've got so far. Here's a basic list of things that I did to use the caustics.

1. Make sure to increase number of Reflections, Refractions, and Max Trace Depth in the Raytracing section of the Quality tab in the Mental Ray render settings.
2. Create scene light (won't use caustics). Turn on Raytrace Shadows. Go to mental ray tab and under Area Light check Use Light Shape.
3. Create a secondary, special spotlight to emit caustic photons (unless you need caustics over a large area).
3a. In spotlight: Decrease intensity to 0, uncheck Emit Specular.
3b. In spotlight mental ray tab: Check Emit Photons.
4. Turn on Final Gather.
5. Go to Render Settings > Indirect Lighting > Caustics. Check the Caustics box.
6. Adjust the photon settings in the spotlight (such as the number of photons (usually 100,000 or more), intensity, etc.)
7. Adjust the Caustics settings in the render settings. Usually use a small radius (such as 0.1 or lower).
8. Go to Render Settings > Quality > Raytrace/Scanline Quality. Increase the Max Sample Level.

Anyway, here's some pictures I've got so far.

Before caustics

With caustics (individual spot lights on each object)

With caustics (with just one area light emitting caustics on all the objects and some tweaked settings)