Render only visible part of object/mesh?

Hi,
i'm looking for a way to render only the visible part of a mesh in the scene (occluded by other objects) (ideally without multiple cameras) to a rendertexture.
Like this:



where i only need the red part (everything else should not be rendered).
Is there any techique i can use to do that?

 

I thought about replacement shaders, but as i haven't used them before, i'm not sure how i'd do it.

 

There's a youtube channel called "Making stuff look good in video games". You'll probably find your answer in those two videos:

Intro to replacement shaders:

Replacement shaders + stencil buffer:

 

Thanks, the second one looks like i can find what i need in it.

 

you can render the occluders only to the depth buffer without writing to the color buffer and then render the object you want to see.

Here's the shader. The important bits are ZWrite = on and ColorMask = 0

Code (CSharp):

1. Shader "litg/Depth Write"
2. {
3.     Properties {
4.     }
5.  
6.     SubShader
7.     {
8.         Tags
9.         {
10.             "IgnoreProjector" = "True"
11.             "Queue" = "Geometry-100"
12.         }
13.  
14.         Pass
15.         {
16.             Cull Off
17.             ZWrite On
18.             ColorMask 0
19.             Lighting Off
20.             Fog { Mode Off }
21.            
22.  
23.             CGPROGRAM
24.  
25.             #pragma vertex vert
26.             #pragma fragment frag
27.  
28.             #include "UnityCG.cginc"
29.  
30.             struct vertexData
31.             {
32.                 float4 vertex : POSITION;
33.             };
34.  
35.             struct fragmentData
36.             {
37.                 float4 position : SV_POSITION;
38.             };
39.  
40.             fragmentData vert(vertexData v)
41.             {
42.                 fragmentData o;
43.                 o.position = mul(UNITY_MATRIX_MVP, v.vertex);
44.                 return o;
45.             }
46.  
47.             float4 frag(fragmentData i) : SV_Target
48.             {
49.                 return 1;
50.             }
51.  
52.             ENDCG
53.         }  
54.     }
55. }
56.  

 

Thanks for the idea, that sounds like something i could use.

 

Stencil is what you need https://docs.unity3d.com/Manual/SL-Stencil.html see example

 

perfect, thanks!