Can't get blending to work

[rich basin]

I'm trying to implement the composition pass as described in this article: https://casual-effects.blogspot.com/2015/03/implemented-weighted-blended-order.html

The shader is supposed to blend its results with the existing data in the texture. The article calls for these blending options

• src blend = SRC_ALPHA
• dst blend = ONE_MINUS_SRC_ALPHA

How have I misconfigured my blending setup? The result I get is the shader replaces the contents of the texture, except the alpha channel is always 1.

[misty geyser]

Is there a demo app you can run through RenderDoc?

[rich basin]

there is, but it's a whole-ass game engine editor

i can try to run it

[misty geyser]

Pain