IItem Renderer API gives you ability to hook into item rendering. More specifically:

• Use GL calls during item rendering.
• Super-ultra-hyper-dynamic rendering.
• Change GUI overlay.

1. Go to releases section.
2. Download API and drop contents into your src/api/java folder.
3. Download DEV jar and drop into your run/mods folder.

• IItem Renderer API has only 2 classes: IItemRendererAPI and IItemRenderer.
• You implement IItemRenderer interface (you CAN use anonymous class), and you give an instance to IItemRendererAPI.registerIItemRenderer() with Item whose rendering IItemRenderer is going to handle.
• You use methods in your IItemRenderer implementation to do stuff.

While mostly everything is the same, there is 1 crucial difference: In forge's 1.7.10 IItemRenderer, you used it to override rendering. Here you use it in conjuction with default rendering. But you can use it to override.

GL Calls Test:

More demos will come in close future