SetReplacementShader not rendering

I’ve been staring at this and looking at example code for an hour, and I can’t figure out what I’m doing wrong. I have this code running on the camera:

Shader overdrawShader = Resources.Load ("Shaders/Overdraw") as Shader;
GetComponent<Camera> ().SetReplacementShader (overdrawShader, "RenderType");

This is the shader it’s calling:

Shader "Overdraw" {
Properties {
    _MainTex ("Base", 2D) = "white" {}
}

SubShader {
    Fog { Mode Off }
    ZWrite Off
    ZTest Always
    Blend One One // additive blending

 Tags { "RenderType"="Opaque"  }
 Pass {
     SetTexture[_MainTex] {
         constantColor(0.1, 0.04, 0.02, 0)
         combine constant, texture
     }
 }

}
}

The objects in my scene all use the Standard shader, so I know they have a “RenderType”=“Opaque” tag.

When the code gets called, the camera doesn’t render anything. What am I missing?

Got it working. Had some things missing from the shader. Here’s the full shader code:

Shader "Overdraw" {
 Properties {
  }
  SubShader {
    Tags { "RenderType" = "Opaque" "Queue" = "Transparent" }
    Blend OneMinusDstColor One
    ZTest Always
    Cull Off
    LOD 200
 
    CGPROGRAM
    #pragma surface surf Lambert

    struct Input {
      float2 uv_MainTex;
    };
 
    void surf (Input IN, inout SurfaceOutput o) {
      o.Albedo.rgb = (0.1);
      o.Emission.b = (0.1);
      o.Alpha = 1;
    }
    ENDCG
  } 
  FallBack "Diffuse"
}