You can control how a mask affects the matte. For example:

• Set the opacity, colour, and edge softness of the mask.
• Specify whether the effect is applied to the inside or outside of the mask.
• Adjust the offset of the mask from its axis.
• Turn a mask on or off.

To set mask options:

1. Display the Matte or Result view.

   
   

2. Select the mask in the image window:
   • Click anywhere on the garbage mask spline.
   • Click the Geom node in the schematic.
3. Access the Garbage Mask menu.

   
   

   (a) Render Mask button  (b) Outside button  (c) Alpha field  (d) Offset field  (e) Splines button  (f) Axis Offset fields  (g) Opacity field  (h) Colour field  

4. Set the mask options. See About Garbage Mask Options.