Improving outline postprocess using stencil operation.

There is excellent tutorial for Outline postprocess.

http://www.tomlooman.com/ue4-outline-post-process/

His technique support pretty outline using custom depth(simliar technique is already being used by editor selected object), and also provide nice multi color feature too.

But what if your game designer want to specify occluders who cause occludee outlined?

Here is my solution.

1. occludee writes team color ID to stencil.
2. occluder increment stencil by 1(to do this, we need to slightly modify custom depth path, PrimitiveComponent has occluder/occludee flag and it is rendered seperately in custom depth path)
3. In PostProcess, only increment stencil pixel is considered as "outlined"

This is very useful when there are too much outline in screen, and we want to use only needed.