How do I use shadows of a light as a mask for other lights in a shader?

Hello,

I am trying to use the attenuation of a light as a mask for rendering.

In my shader I can find the mask-light by comparing its position to a uniform which I set with an external script.
Now I somehow need to "save" the attenuation of this light to mask out everything that is not effected by my mask-light.

This is what I have got so far.

Code (CSharp):

1. Shader "Custom/MySurfaceShader" {
2.  
3.     Properties {
4.         _Color("Tint color", Color) = (1.0, 1.0, 1.0, 1.0)
5.         _MainTex("Main Texture", 2D) = "white" {}
6.     }
7.  
8.     SubShader {
9.  
10.         Tags { "RenderType"="Opaque" }
11.         LOD 200
12.    
13.         CGPROGRAM
14.    
15.         #pragma surface surf MaskLight fullforwardshadows
16.         #pragma target 3.0
17.    
18.         uniform float4 _WorldPlayerPos;
19.    
20.         half4 LightingMaskLight(SurfaceOutput s, half3 lightDir, half atten) {
21.             half4 c;
22.    
23.             fixed NdotL = dot(s.Normal, lightDir);
24.        
25.             // Test if the current light is the mask-light
26.             // if(_WorldPlayerPos.x == _WorldSpaceLightPos0.x && _WorldPlayerPos.y == _WorldSpaceLightPos0.y && _WorldPlayerPos.z == _WorldSpaceLightPos0.z)
27.          
28.             // Use this when the attenuation of the mask-light is > 0
29.             // c.rgb = s.Albedo * NdotL * atten * _LightColor0;
30.  
31.             // Use this when the attenuation of the mask-light is == 0
32.             // c.rgb = half3(0, 0, 0);
33.        
34.             return c;
35.         }
36.    
37.         uniform fixed4 _Color;
38.         uniform sampler2D _MainTex;
39.  
40.         struct Input {
41.             fixed2 uv_MainTex;
42.         };
43.  
44.         void surf(Input IN, inout SurfaceOutput o) {
45.             fixed4 c;
46.        
47.             c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
48.        
49.             o.Albedo = c.rgb;
50.             o.Alpha = c.a;
51.         }
52.    
53.         ENDCG
54.     }
55.  
56.     FallBack "Diffuse"
57. }

Greetings,
Barti

 

The attenuation is not a fixed value. It's different for each vertex with each light source. You can open 'generated surface shader' to see how the atten param is calculate.
In your case, I think the practical solution is to write a custom vertex shader to calculate the mask-light's attenuation manually and use it in the Lighting function.

 

Well, I already tried it and it worked totally fine except for the shadows. I am able to mask everything how I want it but this mask is just a circle without shadows.
If you are able to provide me a solution on how I calculate the shadows, I will definitly take that.

 

try this thread http://forum.unity3d.com/threads/adding-shadows-to-custom-shader-vert-frag.108612/

 

Alright that's it thanks a lot!