Channel > Compound Arithmetic effect

The Compound Arithmetic effect mathematically combines the layer to which it is applied with another layer. The Compound Arithmetic effect is intended only to provide compatibility with projects created in earlier versions of After Effects that use the Compound Arithmetic effect. Using layer modes is usually more effective than using the Compound Arithmetic effect.


Original (left); with effect applied to arch layer, Operator set to Difference, Operate on Channels set to RGB, and Blend with Original set to 8% (center); and with Second Source set to cloud layer, Operator set to And, Operate on Channels set to RGB, and Blend with Original set to 50% (right).

Adjust the following controls for the Compound Arithmetic effect:

Second Source Layer

Specifies the layer to use with the current layer in the given operation.

Operator

Specifies the operation to perform between the two layers.

Operate on Channels

Specifies the channels to which the effect is applied.

Overflow Behavior

Specifies how pixel values that exceed the allowed range are treated. Clip indicates that the values are limited to the allowed range. Wrap indicates that values exceeding the allowed range wrap around from full on to full off, and vice versa. Scale indicates that the maximum and minimum values are calculated and the results are stretched down from that full range to the range of allowable values.

Stretch Second Source to Fit

Scales the second layer to match the size (width and height) of the current layer. If this option is deselected, the second layer is placed at its source's current size, aligned with the upper left corner of the source layer.

Blend with Original

Adjusts the opacity of the second source layer so it blends with the original layer.