AlphaAlpha

Unity Engine
1

i’m wondering if someone with shader knowledge can help me, i haven’t had the time to learn anything about shaders yet - i think this is something simple and i tried to wing it by skimming the docs cutting-pasting from other shaders but i can’t seem to get it to work.

i need a shader that has a maintex with alpha (which i would have tiled) a separate, 2nd alpha channel texture slot as well. its like the two layer terrain, only no second texture (the 2nd alpha mask would not be tiled is for overall transparency not a second texture mix).

i’ve been fooling around with terrains i’d really like to try out some tests with this shader, and like the terrain two layer it doesn’t need 2 uv sets (as an aside - i imagine this could also be a method to have tiled terrains with lightmaps for those of us without maya).

hopefully this isn’t to complex, would anyone be able to put this together for me?

2

What do you want to use these two alphas for? Transparency or something else? How the alphas should be combined (added, multipled, …)?

3

sorry aras, both would be for transparency. i don’t quite understand combine modes with alpha, but i think multiply is what i’m looking for.

4

actually maybe i should describe specifically something i want to apply this to since i don’t understand what i need in shader terminology:

for instance, a large semi-flat mesh representing a cloud:

for the shader:

texture 1 would be tiled:
-rgb for color
-alpha for detailed transparency

texture 2 would not be tiled:
-no rgb needed
-alpha for overall transparency mask, so you don’t see the polys around the edges it just fades out nicely

hopefully that makes sense ; )

5

I think something like this shader could work:

Shader "Alpha/VertexLit TwoLayer" {
    Properties {
        _Color ("Main Color", Color) = (1,1,1,1)
        _SpecColor ("Spec Color", Color) = (1,1,1,0)
        _Emission ("Emmisive Color", Color) = (0,0,0,0)
        _Shininess ("Shininess", Range (0.1, 1)) = 0.7
        _MainTex ("Base (RGB) Trans (A)", 2D) = "gray" {}
        _AlphaTex ("Transparency (A)", 2D) = "white" {}
    }
    Category {
        ZWrite Off
        Alphatest Greater 0
        Tags {Queue=Transparent}
        Blend SrcAlpha OneMinusSrcAlpha 
        ColorMask RGB
        SubShader {
            Material {
                Diffuse [_Color]
                Ambient [_Color]
                Shininess [_Shininess]
                Specular [_SpecColor]
                Emission [_Emission]    
            }
            Pass {
                Lighting On
                SeperateSpecular On
                SetTexture [_MainTex] {
                    constantColor [_Color]
                    Combine texture * primary DOUBLE, texture * constant
                } 
                SetTexture [_AlphaTex] {
                    Combine previous, texture * previous DOUBLE
                }
            }
        } 
    }
}

It is exactly like builtin Alpha/VertexLit, just adds one more alpha-only texture (called _AlphaTex inside the shader). This texture does not modify the color (just takes “previous”), and combines alpha of both textures like: alpha1alpha22.

So if you use the alpha-only texture to control overall transparency, then primary texture’s alpha will work like a detail texture - alpha of 50% in the main texture will mean “don’t change overall alpha”, and lower/higher values will decrease/increase alpha.

6

thank you Aras ; )
i will try this out after work.