This "Hidden Gems" summary covers:
- Rendering Bins (3D layer groups) and Breaks (2D layer pipelines)
- Casting 3D Shadows Onto 2D Layers
- 3D Effects and 2D Layers
- Making Photoshop 3D Layers More Interactive
- Displacement Mapping with FreeForm
You can find more on these topics in 3D layer interactions, render order, and collapsed transformations in AE Help and of course in Creating Motion Graphics with After Effects 5th Edition (reviewed earlier on AEtuts+). There's also extras from CMG itself -- an excerpt from the Parallel Worlds chapter with some extra stuff not covered in the current summary, as well as an Integrating with 3D applications excerpt on importing 3D info from Maya, Cinema 4D, 3ds Max, and other 3D apps.