MayaMan Tutorial: Radiance

This tutorial explains how to get radiance working. We're not creating a pretty scene, but hopefully we're telling you everything you need to know to incorporate radiance in your scenes. An example scene with a reference image can be found in the MayaMan Example Scenes Pack which can be downloaded here

Note, this tutorial assumes a certain level of familiarity with 3D Maya, in particular the ability to create objects, animations and materials i.e. you should be able to build simple Maya scenes.

1. Before commencing, ensure your RenderMan renderers are correctly installed, and that you have performed a successful MayaMan installation.

2. Make sure you have and selected a renderer in MayaMan that supports radiance (eg Entropy).

3. Our simple scens will consist of two perpendicular planes. We will have a light source illuminating one of the planes, and the only thing illuminating the second plane will be the radiance that bounced off the first plane.

4. So, start off by creating two planes in an "L" formation

5. Assign a phong material each to the two planes. Make both materials white and turn off reflectivity for both. For the material that you apply to the vertical plane, reduce ambient colour to zero, and bump up diffuse colour to 5. (You may need to turn this down later, but for now we want to be sure that we see something when we get radiance working)

6. Create a light blue spotlight which is directed towards the horizontal plane in a way that any light that bounces will hit the vertical plane. Make sure though that any direct light only falls on the horizontal plane (this way the vertical plane will only be illuminated if radiance is working)

7. Render a MayaMan preview to make sure your setup renders as described above, light should only fall on the horizontal plane.

8. Now, enable "Radiance" in the MayaMan Global Options in the Global Illumination section. While we're here, reduce the quality settings to the following:
   
   Max Error: 0.3
   Max Pixel Dist: 30
   Samples: 64
   Max Bounce: 1

9. Render another MayaMan preview. You should now see a blurry (and probably blocky) blue-ish pattern on the vertical plane. Now, all you have to do is tweak the parameters in MayaMan Global Options, Global Illumination section, to make the radiance look better, and your renders to take longer... Refer to the documentation of the particular renderer on what the parameters do

10. Note: Radiance is transmitted in the diffuse part of the light calculations. So, if you want to increase/decrease the amount of radiance a partucular surface receives, then the diffuse colour of the receiving object is the parameter you should be changing.

11. Done. If you had any problems/difficulties completing this tutorial, or have suggestions on how to make the tutorial better, or even suggestions for other tutorials, please email support@al.com.au

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