Using Shader Framebuffer Fetch with LWRP

I'm attempting to use Framebuffer fetch on mobile with LWRP. The code example in the docs (https://docs.unity3d.com/Manual/SL-PlatformDifferences.html) is written in CG and it uses SV_Target for the input semantic. This doesn't seem to work in an HLSLPROGRAM when compiling for OpenGL ES 3.1.

When I attempt to compile a simple fragment function like this:

Code (JavaScript):

1. void frag(Varyings input, inout half4 ocol : SV_Target) {
2.     ocol /= 2;
3. }

I get the compiler error: `invalid ps_5_0 input semantic 'SV_Target'`. Does anyone know the correct inout semantic to use or if there's some other mistake here?

 

CoLoR1 works in editor, it now compiles a valid shader but it doesn't seem to run on device. I'll just find another solution until this is supported, thanks for the help.

 

So that still didn't quite work, it seems to generate the wrong GLSL code. If I write the shader directly in GLSL I can make it work:



GLSL:

Code (JavaScript):

1. #version 310 es
2. #extension GL_EXT_shader_framebuffer_fetch : require
3.  
4. precision highp float;
5. precision highp int;
6. layout(location = 0) inout lowp vec4 SV_Target0;
7.  
8. void main()
9. {
10.     float gray = (SV_Target0.x + SV_Target0.y + SV_Target0.z) / 3.0;
11.     SV_Target0 = vec4(gray, gray, gray, 1);
12.     return;
13. }

 

I have a same problem in 2019.3.1f1 and 2020.1.0f1c1.
Change "SV_Target" to "CoLoR" can resolve the compiler error, but it's not work when i generate to GLSL for GLES3.2 android device.
by the way CG is work.

 

sorry i miss the log... it's should be like "vs_SV_Target0" is undefined ? i guess
And my company has the source code, in CompilerHLSL.cpp ParseNeedForFramebufferFetchEnabled , should we add KCoLoRToken to match the "inout <type> <var> : CoLoR" oneliner?

 

Log:
07-30 16:26:57.052: E/Unity(6904): -------- GLSL link error: Error: input vs_SV_Target0 not declared in output from previous stage.
07-30 16:26:57.052: E/Unity(6904): Error: Linking failed.


No, it should work without adding this.[/QUOTE]
My goal is not use framebuffer in HLSL,I want is right generate to GLSL.

I provided two demo, I expect them to achieve the same result, may be is wrong?

 

yes ,i try to transplant to srp
SRP has problem.

HLSLSupport.cginc
#if defined(UNITY_FRAMEBUFFER_FETCH_AVAILABLE) && defined(UNITY_FRAMEBUFFER_FETCH_ENABLED) && defined(UNITY_COMPILER_HLSLCC)
#define SV_Target CoLoR

I found this code, maybe i should define like cg to make generate match SV_Target?

 

anyway is work..but uglily

 

yes , use CoLoR replace SV_Target and keep the code is SV_Target for generate to glsl...great...

 

hi.me again.
about the EXT_shader_framebuffer_fetch, i found the OpenGL document about "How is framebuffer data treated during multisample rendering?" ,the answer was
RESOLVED: Reading the value of gl_LastFragData produces a different
result for each sample. This implies that all or part of the shader be
run once for each sample, but has no additional implications on fragment
shader input variables which may still be interpolated per pixel by the
implementation.
what the "This implies that all or part of the shader be run once for each sample" mean.If I use the msaa x4 and framebuffer fetch ,the pixel shader will be run 4 times for each pixel?

https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_shader_framebuffer_fetch.txt

 

Thank you.
so，that's mean i use both of them, rendering effeciency probably go down a lot.

 

But, usually MSAA runs the fragment program just once per pixel rasterized, open the framebuffer fetch it's going to be 4 times(like the SSAA) ,even if it's only on the edge.this looks terrible...

 

OK，I want talk about OpenGLES,I found this in wiki(but the wiki for OpenGL) about MSAA.
" Unlike supersampling (SSAA) which can result in the same pixel being shaded multiple times per pixel, multisampling runs the fragment program just once per pixel rasterized."
https://www.khronos.org/opengl/wiki/Multisampling
Maybe I made a mistake？

 

HI，I do a test, i create a particle system has 100 particles use the shader that just a simple Blend SrcAlpha One with use framebuffer fetch .I use the particle system full my screen
When the MSAA is off
On my device the run with 30 FPS.
When the MSAA is on
it's just run with 7 FPS
so , it's seems big impact to render efficiency.
shader ps like this:

Code (CSharp):

1.                    
2. void frag(v2f i, inout float4 color : SV_Target)
3. {
4. color += float4(0.5,0,0,1);
5. }
6.  

 

And i found a bug..
when i sample a texture and use buffer fetch together, the shader will error.
like this

Code (CSharp):

1. void frag(v2f i, inout float4 color : SV_Target)
2. {
3.     half4 col = /*2.0f * i.color **/ _TintColor * tex2D(_MainTex, i.texcoord);
4.     col.a = saturate(col.a);
5.     color += (1 - col.a)* col;
6. }

because the layout same location 0,they are conflict.

 

i use the buffer fetch , the "+=" like the blending add.so i'm not use blending.

device is "xiaomi 8 se",gpu:Adreno 616

i have reported this bug to you colleague that on stay my company.I can ask the id to him if you need.