Material Matte Layer is a tool to make much more easy compositing session, think about it like a object matte in c4d compositing tag, but at material level, for example if you have a scene with some back object an one character, with black hole mode you can render a static backgrounds character with in black Hole mode and then you can make another render with character and back in black hole, with this situation if you need to change some thing in character, you can rerender only it and not the back, you can use it to isolate object and fake inclusive or exclusive lighting in various part of the sceneand it can be used to make object and material ID with AA and Physical Camera.

Matte Mode – this option allow choose matte mode:

  • Black Hole – The value of Matte Opacity is ignored, and all the matte for this material is set to be transparent. Use this when you are creating substitute geometry in a scene, which is standing in for objects in a background image that you will be compositing with later. Your stand-in objects will ‘punch a hole’ in the matte. This allows other computer-generated geometry to pass behind your stand-in objects. Later, when foreground and background are composited, the results will be correct, with the background object showing through the ‘black hole’ areas.
  • Solid Matte – This is like Opacity Gain, except that the normally-calculated matte values are ignored in favor of the Matte Opacity setting. The entire matte for the object is set to the value of the Matte Opacity attribute. If there are transparent areas on the object, their transparency is ignored in the matte. Use this setting to composite an object with transparent parts, when you don’t want the background to show through them.
  • Opacity Gain – matte values are calculated in the normal way (based on the transparency of the object) then multiplied by the Matte Opacity.
  • Solid Alpha 

Matte Opacity – is used (along with Matte Mode) to affect how the matte (i.e. alpha channel or mask) for this material will be calculated.

Invert – This option simply inverts the Matte Opacity.

Alpha Transparency – XXX

Invert – This option simply inverts the Alpha Transparency, so transparent and solid areas are reversed. This works for both clipped images and images with built-in alpha channels.