The Child input is unique to Surface Layers and it acts as a way to allow better construction of complex surface layers with subtle interactions between layers. A child is limited to the coverage of its parent, but will also *cover* its parent. You can "nest" child layers as deep as you want, each one in turn limited to the coverage of its parent and likewise covering those further up the chain. For child layers who are "siblings" (at the same level of nesting relative to a common parent), the layers at the bottom will cover those higher up. This is all best visualized in the node list in the Shaders layout accessed from the buttons at the top of the UI. It's rather more confusing at first when viewed through the Node Network. All of this is also covered in more detail in our in-progress documentation:
http://forums.planetside.co.uk/index.php?topic=22The main Input simply takes in the output of the shader before it in the network. This includes color as well as displacement and any other data the previous shader outputs. If the shader it is connected to does not define color itself, then it will generally inherit color from the previous shader. If it does provide color then assuming its coverage is not affected by a Blend Shader or Breakup Shader, it will completely replace the color of the previous shader(s). You use Blend Shader inputs on normal shaders to affect their coverage, and Breakup Shaders on Surface Layers to likewise affect their coverage.
- Oshyan
