Is it possible to avoid writing to certain g-buffers?

Questions & Answers
1

I’m working on a shader that must write an object’s worldspace normals and depth to the corresponding buffers, but leave all remaining g-buffers untouched.

Is this possible?

I’ve added a snippet of my code below to demonstrate what I’m trying to achieve. The problem with this approach is Unity still does write to the other g-buffers (with default values).

Shader "Write Depth and WS-Normals"
{   
    SubShader
    {
        Tags
        {
            "RenderType" = "Opaque"
            "Queue" = "Geometry"
            "LightMode" = "Deferred"
        }      
        Pass
        {
            ZWrite On
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag           
            #include "UnityCG.cginc"
            
            struct appdata
            {
                float3 normal	: NORMAL;
                float4 vertex	: POSITION;
            };
            
            struct v2f
            {
                float3 normal	: TEXCOORD0;
                float4 vertex	: SV_POSITION;
            };
            
            v2f vert ( appdata v )
            {
                v2f o;
                o.normal = mul( unity_ObjectToWorld, float4( v.normal, 0 ) ).xyz;
                o.vertex = UnityObjectToClipPos( v.vertex );
                return o;
            }
            
            void frag ( v2f i, out float depthOut : DEPTH, out float4 normalsOut : SV_Target2 )
            {
                normalsOut = float4( i.normal * 0.5 + 0.5, 1 );
	            depthOut = 1; // Depth established here.
                float alpha = 1; // Alpha established here.

                clip( alpha );
            }
            ENDCG
        }
    }
}
2

You could try making a shader with two passes, one that writes each texture you want, then make a script that uses a command buffer to blit each pass to the corresponding gbuffer texture. Get the example project here Extending Unity 5 rendering pipeline: Command Buffers | Unity Blog and look at how they do the decals. Something like that would probably do the trick.