How to write to RWTexture3D in Pixel Shader

Question

It seems like writing to a RWTexture2D in a pixel shader is possible; I have succeeded in doing this. But when it comes to writing to a RWTexture3D, it doesn't seem to work at all.

 Shader "Custom/RenderToVolume"
 {
     Properties 
     {
         _MainTex ("Diffuse (RGBA)", 2D) = "white" {}
     }
 
     SubShader 
     {
         Pass 
         {
             Tags { "RenderType"="Opaque" }
             Cull Off ZWrite Off ZTest Always Fog { Mode Off }
 
             CGPROGRAM
             #pragma target 5.0
             #pragma vertex vert
             #pragma fragment frag
             #pragma exclude_renderers flash gles opengl
 
             #include "UnityCG.cginc"
 
 
             sampler2D _MainTex;
 
             RWTexture3D<float4> volumeTex;
             float volumeResolution;
             float4 volumeParams;
 
             struct ApplicationToVertex 
             {
                 float4 vertex : POSITION;
                 float4 texcoord : TEXCOORD0;
             };
 
             struct VertexToFragment 
             {
                 float4 pos : SV_POSITION;
                 float4 wPos : TEXCOORD0;
                 float2 uv : TEXCOORD1;
             };
 
             void vert(ApplicationToVertex input, out VertexToFragment output)
             {
                 output.pos = mul (UNITY_MATRIX_MVP, input.vertex);
                 output.wPos = mul(_Object2World, input.vertex);
                 output.uv = input.texcoord.xy;
             }
 
             void frag(VertexToFragment input)
             {
                 float4 color = tex2D(_MainTex, input.uv);
                 
                 float3 volumePos = ((input.wPos.xyz - volumeParams.xyz) / volumeParams.w) * volumeResolution;
 
                 int3 volumeCoords;
                 volumeCoords.x = int(volumePos.x); 
                 volumeCoords.y = int(volumePos.y); 
                 volumeCoords.z = int(volumePos.z); 
                 
                 volumeTex[volumeCoords] = color;
             }
             ENDCG
         }
     }
     Fallback Off
 }

This is what I am trying to do, and it doesn't seem to work, but if I try and write to a 2D texture, it does. Not sure where I am messing it up.

Answer 1

Best Answer

Answer by Daniel-Strayer · Nov 04, 2013 at 08:21 PM

EDIT:

I found that I needed to clear the random write targets AFTER doing my rendering:

 Graphics.ClearRandomWriteTargets();
 Graphics.SetRandomWriteTarget(1, volumeTexture);
             
 orthoCamera.Render();
 
 Graphics.ClearRandomWriteTargets();

This has worked from Unity 4.3

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raja-bala · Sep 09, 2014 at 01:35 AM 0

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has support for writing to it in the pixel shader been added?

fasdfas · Oct 21, 2014 at 07:24 AM 0

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Writing to a RWTexture3D from a fragment shader works for me in unity 4.6, but only using Graphics.Blit. It fails when rendering any other way (for example: Graphics.Draw$$anonymous$$eshNow).

Boltman · Aug 05, 2021 at 03:36 AM 0

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Commenting many years later because this is SO IMPORTANT.

I knew this was possible as I did it ages ago, but I followed multiple guides, NONE of which mention to clear targets AFTER rendering. As soon as I saw this I knew it was the issue because it made so much sense as other things will mess up your texture if you don't unbind it from the register, but still it's one of those things you can't really just know to do without seeing it. I had looked at forums galore with everyone on their own wild goose chase for what the problem is, nobody mentioning anything about it there either. Until finally stumbling on this obscure post with no upvotes or anything with my guy Daniel just putting it right there. Like why is this stuff so poorly thought out and ill documented. Graphics development is always shoved aside for those who like to be tortured.

How to write to RWTexture3D in Pixel Shader

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