Suggestion: Overlay blend rendering for blocks

[muzikbike]

This is a feature from MCPatcher that never ended up making it into Optifine when Optifine became the one-stop shop for resource pack stuff, and it's something I'd very much like to see making a return.

MCPatcher had the ability to allow specified translucent blocks to use the "overlay" blend mode (https://en.wikipedia.org/wiki/Blend_modes#Overlay) rather than the usual alpha blending we see in vanilla. This could be used for custom glass which I think looks a lot better than normal glass, and was notably used by Misa's realistic texture pack in conjunction with connected textures to produce this result:

Here's an example 16x16 texture I threw together a week or so ago as an experiment which also uses overlay rendering:


awesome-glass-demo-1.7.10.zip

Sadly, this feature never made it past 1.7.10 due to MCPatcher's discontinuation and OptiFine never implemented this feature. This is a pity as I find glass textures that utilise it to be far better than if they were to use standard translucency like stained glass does.

The archived source code for MCPatcher is available at https://github.com/pclewis/mcpatcher, so there should be sufficient information in there about how this rendering mode worked. It might be possible to implement overlay-rendered textures as a sixth chunk render layer, such that any desired model can select it (#70) and then use it, which would finally permit a perfect recreation of the 1.7.10 glass. Of course, adding new chunk render layers might screw with other things, so it might need to be toggleable to avoid potential conflicts (or made into a separate mod altogether). This seemed like the best place to suggest this given that it aims to be a replacement for several OF features while also adding in new resource pack capabilities.