Matte passes are often used to create a “cut-out” of one object over another. For example, if you wish to render a car driving along a street, you must create a matte pass of the lamp posts; otherwise, the car render will overlap the lamp posts. The lamp posts’ matte is used to obscure the render of the car so it appears to be behind the posts.
• RGB Matte — Creates a matte pass of selected objects. Matted objects are rendered with their RGB values and unselected objects are not rendered.
This matte is regularly used to composite overlapping objects. Background objects and lights are not rendered, but matte objects are rendered with their original RGB settings.
• White Matte — Creates a matte pass with a constant white RGBA channel of selected objects. Selected objects are rendered white and unselected objects are rendered in black.
This matte is regularly used to composite overlapping objects. The matte pass renders matte objects in white; background objects and lights are not rendered.
• Isolate Matte — Isolates matte information for selected objects. Each matte object is isolated from non–matte objects, meaning that a matte is generated for areas of matte objects that are overlapped by non–matte objects.
All three matte passes include the following settings:
• Background Objects Partition—automatically includes all objects that are not explicitly assigned to the Matte Objects partition.
Visibility is turned off for primary and secondary rays for these objects so that they are rendered as black.
• Background Lights Partition—automatically includes all lights for the scene.
• Partition Matte—these objects are rendered in white, including their shadows and any motion blur defined for them.
The Constant material shader is usually applied to objects in a matte pass partition.
To set up the matte-pass preset
1. Select the object or objects for which you want to create a matte.
2. Load a matte–pass preset from the Render toolbar by choosing Pass > Edit > New Pass > RGBA Matte, White Matte, or Isolate Matte.
All other objects are contained in the Background Objects Partition and are rendered as black.
3. When the Render Pass property editor opens, rename the new pass and, if you wish, set an active camera and render options.
4. When you are satisfied with the settings, preview a fully rendered frame by choosing Render > Preview > All Layers from the Render toolbar.
5. Render the pass. For more information on how to do this, see Rendering Methods.
Autodesk Softimage v.7.5