Geometry Grass Shader: Add a pass to draw the ground.

Hello everyone,

I am trying to make a geometry grass shader (using tesselation) to apply on a Unity Terrain. The grass part is working quite well, but I cannot manage to add a ground surface under it.

Right now I was using a custom mesh for the terrain, so I added two different materials but that's not an optimum solution. And I also prefer to use the Unity Terrain.

Is it possible to add this in one shader ? Because right now the material is only using the first Pass. Either the ground surface or the grass itself.

I don't know if this helps but my shader has a structure like this for now: (I can provide further explanation later on)

Code (CSharp):

1.     SubShader
2.     {
3.         Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalRenderPipeline" }
4.         LOD 100
5.         Cull Off
6.         Pass
7.         {
8.             HLSLPROGRAM
9.             #pragma vertex vert
10.             #pragma fragment frag
11.             #pragma require geometry
12.             #pragma geometry geo
13.             #pragma require tessellation tessHW
14.             #pragma hull hull
15.             #pragma domain domain
16.  
17.             vertexInput vert(vertexInput v)
18.             {
19.                 return v;
20.             }
21.  
22.  
23.             float4 frag(geometryOutput i, real facing : VFACE) : SV_TARGET
24.             {
25.               return float4(1, 1, 1, 1); #to simplify
26.             }
27.          }
28.  
29. +Additionnal pass for shadows
30.      }

 

So I just learned that URP does not support multi pass shaders...

I found an alternative solution to have 2 passes in URP shader, it might help someone:
in the first pass I use the Tags {"LightMode" = "UniversalForward"}
and in the 2nd one no tag so the two get rendered.

I found this on a post from 1 or 2 years ago, so maybe there is a better alternative for this right now.