What's the correct "final step" in a premultiplied alpha blending shader to respect vertex colours?

[GroZZleR]

I’m having an issue with a premultiplied alpha blending shader for the UI I’m tinkering with that won’t respect the CanvasGroup’s alpha.

Normally the “final step” would be:

half4 final = results * IN.color;

I’m guessing I need to do something a little different because of the premultiplied alpha blending but I’m not sure what.

Thanks.

[bgolus]

@GroZZleR

premultiplied alpha

Premultiplied alpha blending assumes the color has been premultiplied by the alpha, hence “premultiplied alpha”. If you want the vertex alpha to act like alpha blending, then:

half4 final = results * IN.color;
final.rgb *= final.a;

[GroZZleR]

Brilliant. Thanks mate.