Completly invisible shader, but only shows lights reflection on it

Hi everyone,

Is it possible to write a shader that is completly invisible, but only shows lights reflection on it as the example below ?

Before applying shader


The plane is fully transparent, but it reflects the white light part, as a white diffuse


Real time result



Anyone know if something like that already exists ?

Thanks!

 

I found this shader here to show lighting only:

Code (CSharp):

1.     Shader "Lighting Only" {
2.         Properties {
3.             _Color ("Main Color", Color) = (1,1,1,1)
4.             _MainTex ("Base (RGB)", 2D) = "white" {}
5.         }
6.      
7.         SubShader {
8.             Blend SrcAlpha One
9.             ZWrite Off
10.             Tags {Queue = Transparent}
11.             ColorMask RGB
12.             // Vertex lights
13.             Pass {
14.                 Tags {"LightMode" = "Vertex"}
15.                 Lighting On
16.                 Material {
17.                     Diffuse [_Color]
18.                 }
19.                 SetTexture [_MainTex] {
20.                     constantColor [_Color]
21.                     Combine texture * primary DOUBLE, texture * constant
22.                 }
23.             }
24.         }
25.      
26.         Fallback "VertexLit", 2
27.      
28.     }
29.  

Here is the result with "Lighting Only" shader:



I still have 2 problems with it, the light result is not clean (low definition?), and this shader does not accept shadows (unlike "Diffuse" shader) :


Thanks in advance

 

After multiples tests I finally found this, witch seems to be perfect:





Good result, but it still not recieves the projected shadow from the cube, any ideas ?

Code (CSharp):

1.      Shader "FX/Matte Shadow3" {
2.     Properties {
3.     _Color ("Main Color", Color) = (1,1,1,1)
4.     _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
5.     _Cutoff ("Alpha cutoff", Range(0,1)) = 0.01
6.     _ShadowStrength ("Shadow strength", Range(0,5)) = 1
7.     }
8.     SubShader {
9.     Tags {"Queue"="AlphaTest" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}
10.     LOD 200
11.     Blend Zero SrcColor
12.     CGPROGRAM
13.     #pragma surface surf ShadowOnly alphatest:_Cutoff
14.     fixed4 _Color;
15.     float _ShadowStrength;
16.    
17.     struct Input {
18.     float2 uv_MainTex;
19.     };
20.    
21.     inline fixed4 LightingShadowOnly (SurfaceOutput s, fixed3 lightDir, fixed atten){
22.     fixed4 c;
23.     c.rgb = s.Albedo*atten;
24. //    c.rgb = lerp(_ShadowStrength *.75, 1, atten).rrr;
25.     c.a = s.Alpha;
26.     return c;
27.     }
28.    
29.     void surf (Input IN, inout SurfaceOutput o) {
30.      //fixed4 c = _LightColor0 + _Color;
31.      fixed4 c = _LightColor0 + 0.3*_Color;
32.      //fixed4 c = _Color;
33.     o.Albedo = c.rgb * _ShadowStrength;
34.     o.Alpha = 0;
35.     }
36.     ENDCG
37.     }
38.     Fallback "Transparent/Cutout/VertexLit"
39.     }

 

For anyone still struggeling with this and want a shader that is 2 sided transparent but still show the light glow, I changed the above shader a bit to make it work:

Code (CSharp):

1.  Shader "FX/Matte Shadow3" {
2.     Properties {
3.     _Color ("Main Color", Color) = (1,1,1,1)
4.     _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
5.     _Cutoff ("Alpha cutoff", Range(0,1)) = 0.01
6.     _ShadowStrength ("Shadow strength", Range(0,5)) = 1
7.     }
8.     SubShader {
9.         Tags{ "RenderType" = "Transparent" "Queue" = "Transparent" }
10.         LOD 100
11.         Blend srcAlpha oneMinusSrcAlpha
12.         ZWrite Off
13.  
14.         CGPROGRAM
15.         #pragma surface surf ShadowOnly alphatest:_Cutoff
16.        
17.         fixed4 _Color;
18.         float _ShadowStrength;
19.  
20.         struct Input {
21.             float2 uv_MainTex;
22.         };
23.  
24.         inline fixed4 LightingShadowOnly (SurfaceOutput s, fixed3 lightDir, fixed atten){
25.             fixed4 c;
26.             c.rgb = s.Albedo*atten;
27.         //    c.rgb = lerp(_ShadowStrength *.75, 1, atten).rrr;
28.             c.a = s.Alpha;
29.             return c;
30.         }
31.  
32.         void surf (Input IN, inout SurfaceOutput o) {
33.             //fixed4 c = _LightColor0 + _Color;
34.             fixed4 c = _LightColor0 + 0.1*_Color;
35.             //fixed4 c = _Color;
36.             o.Albedo = c.rgb * _ShadowStrength;
37.             o.Alpha = 0;
38.         }
39.  
40.     ENDCG
41.     }
42.     Fallback "Transparent/Cutout/VertexLit"
43. }

It can be better but I'm just starting to learn

Make sure you set alpha cutoff to 0 (zero) for it to work properly.

 

Anyone found a solution that supports shadows?