Composite is meant to be used in conjunction with other effects applied before Composite. To use Composite, apply an effect/effects to the layer, apply Composite and select composite method.
Opacity: Use this control to determine the transparency of the original source layer in the composite.
Composite Original: Use this pop-up menu to select which composite method to use between the effect/effects and the source layer. Each offers a different result. In addition to Copy, Behind and In Front, Composite supports all the standard AE Transfer Modes, except for Dissolve.
RGB Only (Supervised): Use this check box to determine if the source layers alpha channel will be included in the composite. This control is disabled if selected transfer mode involves the alpha channel. The default setting is RGB only, meaning that the
alpha channel is ignored.