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# MayaMan Tutorial: Caustics

This tutorial explains how to render caustics using MayaMan. 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 enabled raytraced reflections in the Maya Render Globals, and selected a renderer in MayaMan that supports caustics (eg Entropy).

3. Build a simple scene consisting of a ground plane and a short, un-capped cylinder with a fairly large radius, sitting flat on the ground plane. This cylinder should produce a cardiac pattern on the ground when we're done.

4. Create two plain materials in HyperShade, and assign them to the objects. You don't have to change the default settings.

5. Create a pointlight and translate it to a location which is to the right of, and above the cylinder.

6. To be able to use caustics in the scene, we first have to enable it in the MayaMan Global Options, under the MayaMan Global Illumination Options tab. Notice the NGather and Max Pixel Dist values. You will most probably have to tweak these to get the effect you want. Please refer to the renderers documentation for more info on what these parameters do

7. Select the light and add a MayaMan Light Attributes using the MayaMan menu. Open the Attribute Editor for the light, switch to the MayaMan Light Attributes tab, and change the number of photons to be shot from this light. 20 000 seem like a nice and round number for our test, for PRMan users this number only has to be non zero, the actual number of photons shot is controlled by a global setting and the renderer will decide how many photons each light will generate.

8. You are also required to mark/tag which models will show caustics. You do this by attaching a MayaMan Model Attributes node to the object (the ground plane in this example) and enable the "receives caustics" option in the Attribute Editor.

9. PRman users will also have to nominate which surfaces photons will bounce from (the shading model), to do this add a MayaManAttributes node to the cylinder and under the 'PRman11 Specific' section of the Caustics and set the Photon Shading Model to 'Chrome'.

10. Do a MayaMan preview. The caustics should now appear, but will most probably need some tweaking. The parameters that will directly affect the appearance of the caustics are the number of photons used (light attributes) and NGather/Max Pixel Dist (global options).

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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