MayaMan Tutorial: Shadow Cheating

This tutorial explains how to use shadow maps from other lights in order to "fake" the shadows from a particular light. 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.

Before commencing, ensure your RenderMan renderers are correctly installed, and that you have performed a successful MayaMan installation.
Start off by creating a ground plane and put a cone on the plane. Scale the cone up in the y-direction and down in the x/z-directions
Create a spotlight that points towards the cone. Enable depth map shadows for the light.
Do a MayaMan preview render. You should get exactly what you expect, ie a cone with a normal shadow.
Now, add a MayaMan Light Attributes node to the light, and browse to the Shadow Location Cheating section using the Attribute Editor. Click "enable shadow cheating".
Click on the small checker box next to ShadowCheater_0. This will create a new light. Orient that light so that it is pointing towards the cone from a completely different direction.
Do another MayaMan preview render. You should now see that the cone is still illuminated from the same direction as before, but its shadow is generated from the second light.
You can continue and add additional lights in the same way, using the MayaMan Light Attributes Node (all lights created from this Light Attributes node will share the same Light Attributes node) for each additional shadow that you want to create.
You will notice that the shadow is very noisy. You can reduce the noise by increasing the number of samples (also found in the MayaMan Light Attributes) and choosing a Gaussian filter instead of the default Box filter. You may also have to change the dmap filter size, dmap bias, and/or depth map resolution in Maya's own Light Attributes.
Note on using Entropy: you may find that you have to disable "Casts Shadows" in Maya's Render Stats for the ground plane to get depth map shadows to show up properly when rendering with Entropy.
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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