Use source nodes in Action to create more advanced techniques such as transforming or replacing a front or matte clip or applying motion blur. Source nodes can be used to separate front and matte clips in media and then apply separate transformations to each clip. For example, if you apply media to a surface and you want to create an effect where the matte moves into the scene, add a source that isolates the matte clip. A matte source lets you animate the matte's position separately from the front. You can also use source nodes to apply several matte clips to a single front clip.
Source nodes are applied before any Media list effects, such as the Modular Keyer, and may lead to unwanted effects. For example, a Modular Keyer effect applied on a media layer is also applied to the Source node. If you do not want to apply the Modular Keyer effect on a Source node, you need to create a new media layer for the source node output.
When working with Source nodes, global Scene Ambient lighting has no effect. Therefore, when you add a Source node, a Light node parented to a Camera node is automatically attached to the Source node. This light is an ambient type, and appears at half the distance of the source camera.