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BartronPolygon
New Participant
April 12, 2022

Passthrough and URP transparency: does anyone have this working?

Having a lot of trouble getting alpha blending (alpha or additive) working with URP. The built-in Unlit shader actually works and blends fine. But I'm working with some simple Shader Graph shaders downloaded from the asset store that aren't doing anything fancy, have Surface set to Transparent, and Blend to either Additive or Alpha. They don't blend with the passthrough underlay at all, rendering as ugly black backgrounds instead. It's almost as if they are not rendering out their alpha values for subsequent compositing but I don't see why. 

 

Has anyone found a fix? Are there some special considerations to take into account when using the passthrough layer?

 

Note that when I re-enable the skybox, the objects blend just fine over it.

3 replies

goodm914900
New Participant
April 20, 2023

Anyone has found solution? I'm fighting with the same issue

    Inhouse1343491
    New Participant
    June 21, 2023

    This is the only reference to this problem on the entire web, which seems weird.  So I reached out to BartronPolygon and he was really helpful about what the problem is. I have a work around...

    The problem is that even though the shader is additive, it is blended with the passthrough layer using the alpha channel. So basically, your additive shader becomes an alpha blended shader when composited with passthrough. 

    The workaround is to basically just treat it as alpha blended. Saturate the colour channels (No dark colours), and use the alpha channel to fade. This isn't additive, and it doesn't quite have the same effect - the colours are replacing the passthrough, rather than adding to them. However, it does avoid the dark tinges that you get if you try and feed in dark colours.

    Below is a glow shader using this method.
    Below that is what the equivalent would look like in photoshop. 

      Synergiz
      Inspiring
      October 30, 2023

      Hi, same issue here, but the "fade" fix didn't work (it fades to...black ^^") How can I make this shadergraph work with passthrough (this is a blur effect, blendingmode=alpha) ?

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