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1 - First we setup a very simple scene. A plane, a sphere and one light. For this exemple I choose a Directional Light but the same thing is possible with SpotLight or PointLight.
You'll also need a Locator.
2 - We create now, a new SLIM palette.
Render > RenderMan > Slim > NewPalette.
Setup some Appearance and attach 'em to objects in the scene.
3 -If you have it in your shelf, Hit the RenderMan Render button .
Above you see what I get with my setting.
4 -Now, imagine we want the sphere to disapear as the animation goes.
The technique is simple when you want a parameter to be animated you need to connect this parameter to an attribute in Maya. And instead of keyFraming the MtoR parameter you add keys to the Maya attribute.
when done you write a little TCL expression to make the connection.
Here is the methodology :
In Maya, select the Locator and add a Custom attribute.
Modify >addAttribute
Attribute Name : Opacity
Float
Min:0
Max:1
Default:0
5 - Set some KeyFrames to the Opacity Attribute:
Current Time 1 => Opacity 1
Current Time 40 => Opacity 0
6 - When done we go Back to our Slim Palette.Double click the shader attached to the sphere. (Mine is a simple plastic shader).
Change the Opacity Attribute from Constant to Expression.
IT WORK ! But ...
The Shadow is still opaque so the result is imbelievable.
You can use the same trick to animate the shadow color to create a transparant one.
I added a ShadowCTR Custom Attribute and animated it and add the same kind of TCL expression to the shadow color parameter of the Light shader.
Here you can download the resuling animation
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