Outline shader where only the outline renders and the mesh is invisible ?

I've looked at a lot of outline shaders this afternoon and tried amending them to get this effect - but no dice - I always end up with the block colour vertex-fattened inital pass showing. Wheras I just want a nice outline with *nothing* inside it.

Could someone point me in the right direction ?

thanks X

 

The easiest way to do this is with stencils.

Most outline shaders require two passes, one for the object and one for the outline. This would be no different. However the first pass would be the object writing to the stencil buffer, but otherwise invisible. And the second pass would be the outline set to not draw anywhere the stencil has been written to.

Code (csharp):

1. Pass {
2.   // write 1 to the stencil buffer only where it's not already set
3.   Stencil {
4.     Ref 1
5.     Comp NotEqual
6.     Pass Replace
7.   }
8.   ColorMask 0 // don't render to color
9.   ZWrite Off // don't render to depth
10.   // ZTest Always // if you want the outline to appear through walls
11.  
12.   CGPROGRAM
13.   #pragma vertex vert
14.   #pragma fragment frag
15.  
16.   #include "UnityCG.cginc"
17.  
18.   float4 vert (float4 vertex : POSITION) : SV_POSITION { return UnityObjectToClipPos(vertex); }
19.   fixed4 frag() : SV_Target { return 0; }
20.   ENDCG
21. }
22. Pass {
23.   // only render where the stencil hasn't been set to 1
24.   Stencil {
25.     Ref 1
26.     Comp NotEqual
27.   }
28.   // ZTest Always // if you want the outline to appear through walls
29.  
30.   // the rest of the outline shader pass
31. }