Why can we add vertex alpha if there are no proper shaders?

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I have been playing with procedural mesh-building, and have gotten to the point that I am satisfied that my normals are calculating correctly, my UV mapping is good, and I want to bring it to the next level by adding additional triangles that use the vertex alpha value to blend.

Unfortunately, the shader projects that I have found that actually use the alpha value also seem to touch the whole mesh with a fade, rather than only the triangles assigned to the low alpha. (Also some funky clipping going on that doesn't happen with non-fade shader). <-discovered just now this has to do with the draw-order vs depth.

Does anyone have a simple solution to this? Seems odd that we have a piece of data that is not easily used.

Thanks in advance! ps. my searches have let to lots of complicated shader programming that I am not really up to. I just want one that uses the alpha for the alpha!

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Answer by Zynek · Nov 05, 2016 at 08:53 AM

Simple things sometimes means a lot of work, i would suggest splitting mesh into 2 - one with trapnsparent triangles and other with standart shader.

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CodeSlacker · Nov 05, 2016 at 08:16 PM 0

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I think you are right. Trial and error agrees with your conclusion!

I have to create the triangles within the mesh anyway, so the best solution seems to be to have UV0 mesh be the regular opaque stuff, and UV1 use a vertex alpha fade for the overlay.

Hey, and bonus - for UV0 I don't have to set all the vertices to a color / alpha of 1, 1, 1, 1 because the shader won't need that info!

Why can we add vertex alpha if there are no proper shaders?

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