Texture with solid color for image's alpha?

Unity Engine
1

OK, I don’t know if it’s just too late or I’m stupid.

Basically here is my issue simplified. Lets say I have a plane, and I UV mapped it, that works great. My texture is just a big red circle with alpha around it.

If I use a diffuse shader, it works great, but all the alpha does is become black. If I change the color in the diffuse shader, it changes the tint of the red texture, but the alpha is all black. What if I wanted the alpha to be orange? Basically I want my texture to apply to a background color material like a big sticker, that I change the color of.

I’d actually want it to be specular on the background color and image.

I’ve played with all the standard shaders and nothing seems to be like this. I’m pretty sure I could write my own CG shader, but I want to make sure I’m not going crazy first.

Thanks for any insight!

-Michael

2

Well, I ended up just modifying the standard specular shader to do what I wanted:

Shader "Custom/Sticker Specular" {
Properties {
    _Color ("Main Color", Color) = (1,1,1,1)
    _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1)
    _Shininess ("Shininess", Range (0.03, 1)) = 0.078125
    _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {}
}
SubShader {
    Tags { "RenderType"="Opaque" }
    LOD 400
  
CGPROGRAM
#pragma surface surf BlinnPhong


sampler2D _MainTex;
fixed4 _Color;
half _Shininess;

struct Input {
    float2 uv_MainTex;
};

void surf (Input IN, inout SurfaceOutput o) {
    fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
    if (tex.r < 0.01 && tex.g < 0.01 && tex.b < 0.01) {
        o.Albedo = _Color.rgb;
    } else {
        o.Albedo = tex.rgb;
    }
  
    o.Gloss = tex.a;
    o.Alpha = tex.a * _Color.a;
    o.Specular = _Shininess;
}
ENDCG
}

FallBack "Specular"
}

So basically I just detect if the color in the texture is pretty much pure black, and if it is that is the “transparent” area around the image I want to be the color set by _Color. I get specular on the image and surrounding colored area this way.

Can anyone tell me why this didn’t work though:

if (tex.a < 0.1 ) {
o.Albedo = _Color.rgb;
} else {
o.Albedo = tex.rgb;
}

I had to replace the alpha with black and remove alpha channel from my png and then check if it was black, it’s like it never would realize there was an alpha value or something.

Is this the best way to do this? I’m not sure how bad it is to use the if else like that…

3

Try the following, replace the if with the following code. It should work.

o.Albedo = (tex.rgb * tex.a) + ((1 - tex.a) * _Color.rgb);

4

Thanks, it worked!

So basically if you can think of “math” to do the trick of if/else statements, it’s a lot more efficient as well?

5

If you can think in Maths then you can solve very large if/else into a compact form. :slight_smile: