Chroma Key

Hi,
I am not confortable with Shaders, but what I want to do needs them.

I want to create a chroma key shader to remove all the green part of a texture and replace it with alpha.

Actually, I managed to remove all the green in the texture, but it removes all the green layer. I only need to keep the green layer on the picture inside my texture. (like a green background in the movies)

Code (csharp):

1.  
2. Shader "Custom/ChromaKey" {
3.  
4.     Properties {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         _Color ("Color", Color) = (1,1,1,1)
7.     }
8.  
9.     SubShader {
10.         Tags {
11.             "RenderType" = "Transparent"
12.         }
13.      
14.         Lighting Off
15.         ZWrite Off
16.         Blend SrcAlpha OneMinusSrcAlpha
17.      
18.         CGPROGRAM
19.         #pragma surface surf Lambert
20.  
21.         sampler2D _MainTex;
22.         float4 _Color;
23.  
24.         struct Input {
25.             float2 uv_MainTex;
26.         };
27.  
28.         void surf (Input IN, inout SurfaceOutput o) {
29.             half4 c = tex2D(_MainTex, IN.uv_MainTex);
30.             o.Albedo = c.rgb;
31.             o.Alpha = lerp(o.Albedo, _Color, c.g);
32.         }
33.         ENDCG
34.      
35.     }
36.  
37.     FallBack "Diffuse"
38. }
39.  

Thank you in advance for your help.

 

you probably want to clip the transparency rather than blend it