Help with Shader (Depth rendering with alpha and intersection)

Unity Engine
1

Hi everyone, how are you?, hope you’re fine, well, I have this problem with this shader, I was struggling and trying to understand what is the piece I need to change to achieve the wanted effect, you’ll see, this is a “Thickness” shader that works rendering the depth of an object mesh with color, I modified the code to give it color but something in one of the functions is not working as I expected, when the object intersect another object this intersection appears in negative, I tried to change some parameters as Culling or ZTest, that isn’t in the code, in some way it worked but, object interpose to another or when I move camera away from object it loses is color…

I’m using URP.

This is how shader works:

723×317 12.2 KB

And this is the wanted effect:

723×317 11.4 KB

And this is the shader, isn’t mine, I guess I’m not the only one who was searching:

Shader "Custom/Thickness" {

    Properties {
        _Color ("Main Color", Color) = (1,1,1,1)
        _Absorption("Absorption", Range(-10, 10)) = 1
    }

    SubShader {
        Tags {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "Transparent"
        }

        Pass {
            Cull Off
            Blend One One
            Lighting Off
            ZWrite Off
            Fog { Mode Off }
          
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
           
            fixed4 _Color;
            struct a2v {
                float4 vertex : POSITION;
            };
            struct v2f {
                float4 pos : SV_POSITION;
                half dist : TEXCOORD0;
            };
            v2f vert(a2v v) {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                COMPUTE_EYEDEPTH(o.dist);
                return o;
            }
            float _Absorption;
            fixed4 frag(v2f i, fixed facing : VFACE) : COLOR {
                float depth = -_Absorption * sign(facing) * i.dist;
                return _Color * depth;
            }
            ENDCG
        }
    }
}

Any advice is welcome :slight_smile: .

2

That shader only works if both the front and back of a mesh is visible. If the mesh is intersecting with a surface, like in your example, the hack it’s using to do its “thickness” effect falls apart.

There is no work around for this, and there are no single-shader solutions for “thickness” rendering that otherwise exist.

3

Damn, well, thanks for the explanation, I’ll be back if I have a solution :slight_smile: .