Using alpha channel or luminance values for a track matteDefine transparency in a track matte using values from either its alpha channel or the luminance of its pixels. Using luminance is useful when you want to create a track matte using a layer without an alpha channel or a layer imported from a program that can't create an alpha channel. In both alpha channel mattes and luminance mattes, pixels with higher values are more transparent. In most cases, you use a high-contrast matte so that areas are either completely transparent or completely opaque. Intermediate shades should appear only where you want partial or gradual transparency, such as along a soft edge. To create a track matte:
No Track Matte No transparency created; next layer above acts as a normal layer. Alpha Matte Opaque when alpha channel pixel value is 100%. Alpha Inverted Matte Opaque when alpha channel pixel value is 0%. Luma Matte Opaque when a pixel's luminance value is 100%. Luma Inverted Matte Opaque when a pixel's luminance value is 0%. After Effects converts the next layer above into a track matte, turns off the video of the track matte layer, and adds a track matte icon ( Note: Although the video is turned off for the matte layer, you can still select the layer to reposition, scale, or rotate it. Select the layer in the Timeline window, and then drag the center (indicated by a circle with an X) of the layer in the Composition window. |