Using the Shadow Matte Shader

The Shadow Matte shader lets you capture shadows created by using 3D objects as proxies. This creates the illusion of shadows cast from objects or image elements onto 2D images where none exist. The resulting output using this shader is a black and white image that shows the shadows in black, and everything else in white.

For example, if you have an image of a cityscape, and you want to have a red balloon fly overhead, casting a shadow as it travels, you could create your balloon using a sphere, add a light source to illuminate it, and then add a planar surface parallel to the ground to receive the shadow. You would then select the Shadow Matte shader to use on the plane, and set the Blending Mode to Multiply to mask out the plane, except for the shadow. You can then animate the sphere, and the shadow will follow it.

To set Shadow Matte parameters:

1. Select the Materials tab.
2. Select a layer from the Layer Editor, and then select the Shadow Matte shader.
3. Set parameters to control how light or dark the shadow should look, and to invert the shadow.

   Parameter	Description
   Multiplier	Uniformly scales the lightness or darkness of the shadow up or down.
   Invert Shadow	Flips the shadow inside out to reveal the background in the shadow regions and mask the illuminated areas.