Shaders work in Direct3D but not in DesktopGL

Satoshi · June 18, 2022, 10:13am

It works fine in DirectX projects.
However, in the DesktopGL project, I get an error at runtime.

Please let me know where I can correct this.

My final target is iOS and Android, but it occurred while trying to create a test environment with DesktopGL first.

AlienScribble · July 17, 2022, 6:27pm

Wondering if you got it working. I know there are some tiny adjustments I had to make with DX and DesktopGL versions of my shaders. Wondering which runtime error it showed (sometimes that can be misleading btw).

Satoshi · July 20, 2022, 7:40am

I was able to solve the problem with the compute shader version you gave me below.

In the official MonoGame version, the presence of “constants used only by pixel shaders” resulted in an error at runtime.
This problem was solved by using the Compute Shader version.

Note that the compute shader version also had some limitations, such as not being able to use arrays, so some tweaking was necessary.

github.com

cpt-max/Docs/blob/master/Migrating shaders to ShaderConductor.md


# Migrating Shaders from MojoShader to ShaderConductor

This only applies to OpenGL platforms.<br>
You don't necessarily have to migrate existing shaders, as MojoShader is still included. If all shaders in a file are shader model 2 or 3 MojoShader will automatically be used for shader compilation. This should ensure full backwards compatibility for existing projects.
You can mix MojoShader and ShaderConductor shaders in the same project, only ShaderConductor can handle shader model 4 or 5 though.
<br>

The moment a single shader in the file is set to shader model 4 or higher, the entire file will be compiled through ShaderConductor. So if you mix SM 3 and SM 4 shaders in the same file, even the SM 3 shaders will be compiled through ShaderConductor. It is recommended to switch all shaders in the file to SM 4 or higher simultaneously, because SM 2 and 3 support is not that great with ShaderConductor (see SM 2 and 3 limitations below). 
<br>

ShaderConductor compilation does not require Wine on Linux or Mac, so forcing ShaderConductor compilation for pure SM 2 and 3 files can still be useful.
You can force ShaderConductor compilation by adding the <b>CONDUCTOR</b> define to the effect processor by: 

- using the MGCB editor UI: Effect Properties -> Processor Parameters -> Defines
- adding <b>/processorParam:Defines=MOJO</b> to the mgcb file in the corresponding effect block
- adding the <b>/Defines:MOJO</b> argument when calling MGFXC directly via command line
<br>

In order to compile using ShaderConductor the following modifications to the HLSL source are neccessary, mainly because the new HLSL compiler from Microsoft (DXC) does not support the old DX9-style syntax anymore.

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Note that the problem has been resolved for Windows and DesktopGL, but is still trial and error for Android (OpenGL ES).

AlienScribble · July 22, 2022, 12:56am

Ah cool, I’m glad you got it working. Altho I’m wondering: If it’s the " SkinnedModelEffect.fx" file that caused runtime error in desktopGL - it seems a bit strange since I did mine on desktopGL and it worked. I’m not sure what you meant by: “presence of “constants used only by pixel shader”” causing an error since I don’t seem to have encountered that unless I’m misunderstanding something. I guess using ShaderConductor’s the best way to go though since it higher SM’s means more power.