Passthrough per pixel instead of full screen blend

[daniel5gh]

As far as I understand, currently passthrough works only with a full screen blend, using (pre)multiplied blend mode.

I'd like to add passthrough alpha values per pixel and I would like to know a couple of things first.

1. Are there already plans or people working on this?

2. I am totally new to the code base. Am I on the right track if update the alpha value for the resulting pixel to anything other than 1.0?.

   ALVR/alvr/graphics/resources/stream.wgsl

   Line 130 in d3333c5

   return vec4f(color, COLOR_ALPHA);

My plan is to after I have a dev setup going, to start with a simple Chroma key algo hard coded in the shader. Next I would like to update its parameters from the GUI on the Dashboard similar to how you now select the blend mode and alpha value. Then look at alternative ways of deciding the alpha value for better control by users.

I have a bunch of experience with most or all used technologies in this project.

Any suggestions are welcome!

Thanks in advance.

[zmerp]

Chroma keying is implemented in #2662 and it will be merged soon

[daniel5gh]

awesome! I am glad I asked first 😄

And I thought I had searched PRs too, apparently not.

[daniel5gh]

I just set up a build/dev environment and I just wanted to say what a delight that experience was. Followed the wiki and worked in one go.

I have tested your chroma-key PR on Pico4 ultra and windows 11 and it works like a charm. I love how I can change and tune the PT settings in real time.