OctaneRender® for Blender

The Output AOV node connects to the Output AOV Group node which is then connected to the a Output AOV Group Output node (figure 1). The Output AOV node is used to assemble results of generated AOVs using Render AOV nodes. Additionally, other compositor nodes can be added to the Output AOV node such as post-processing effects. In figure 1, two different compositing trees are set up. One compositing tree add bloom on top of Diffuse and Reflection AOVs and the other adds glare on top of the same Diffuse and Reflection AOVs. 

Figure 1: An set of two Output AOV compositing trees

Multiple layers can be added via the Add Layer button. Layers can be removed with the Remove Layer button. When a layer is added, a new input pin will appear at the top of the current layer pin(s). Each set of Output AOV nodes are available for viewing in the Render Viewport when they are connected together using the Output AOV Group node (figure 1).