Lightmap Masking Custom Filter Issue

[Roomy]

Hey, so, I have a relatively simple problem:

I want to cut the solid parts of a lightmap out of a darkness layer, usually one solid color. This can't be done without alpha compositing unless you use custom filters, so I decided to give it a crack. I got a version working in 3.0.0 PIXI (based off of an old lightmap filter), but when transitioning to 5.2.2, I'm experiencing all kinds of problems, namely that the lightmap, despite logging/extracting/etc. as the expected picture, seems to be treated as pure white by the filter.

You can find my demonstration here: https://codepen.io/roomyrooms/pen/mdOQggP?editors=0010

As you can see, setting the alpha of the darkness layer to the lightmap's alpha per-frag makes it invisible, completely. It doesn't seem to be interpreting the lightmap at all. Any help? Apologies, I'm a newbie to shaders/webgl/pixi/everything! 

For those curious, here's a working version in 3.0.8: https://codepen.io/roomyrooms/pen/NWbmKLj?editors=0010

Edited March 15, 2021 by Roomy

[Roomy]

I managed to get it working!!!
https://jsfiddle.net/roomyrooms/z7n3fuqt/49/

It takes a lightmap, a tilemap (just the background) and a darkmap (a sheet of a single color) and renders the lightmap's black values as transparency in the darkmap, effectively punching holes in it just the way I wanted. Woohoo!

[ivan.popelyshev]

My big example of how to make lights by modyfing filters and using pixi-layers: https://codesandbox.io/s/tender-franklin-iycmu