Autodesk 62205-051408-9001 User Guide - Page 250

10 Using Masks Combustion offers masking tools with high precision and total control. Typical tasks such as wire and rig removal become easier, and a world of custom effects becomes available. About Masks Use a mask to isolate a region of an image, and make the rest of the image completely transparent. The mask affects the image's alpha channel, which is where the transparency information is stored. You can use a mask to create the alpha channel, or you can use a mask to add to an alpha channel. Inverted Mask (Outside is Opaque) You can use the isolated region from a mask in a composite. For instance, use masks to make the sky in a foreground clip transparent and then place a more dramatic sky in the background. Original image with plain Image with masked out sky blue sky. (black area is transparent). Mask (Outside is Transparent) The inside of the mask has an opacity between 0 and 100%, while the outside has an opacity equal to 0%. When you invert a mask, you make the rest of the image completely opaque. You still control the opacity of the inside of the mask. Composite over dramatic sky. If you simply want to isolate a region of an image without affecting the transparency, use a selection instead of a mask. When you apply an operator (such as a Color Corrector) above the selection, only the isolated area is affected and the rest of the image is still visible. For more information on selections, see Chapter 19, "Paint: Drawing Selections''. When you key a blue-screen image, you can use masks to isolate the regions you want to either key out or leave in the key. As you clean up the matte, you 234