Libretro Slang Documentation Open Discussion

anikom15 · 25 February 2026 18:33

Sorry I don’t mean to offend anyone’s hard work. I just wanted to offer something back to the community based on my own shader experience. Of course we have documentation for the Slang format here: Slang Shader Development. But it doesn’t cover everything, so I tried to improve it here by asking Github Copilot to read it and give me follow-up question a hypothetical developer might have. So I tried adding new content and clarifying how it all works. This was the result:

github.com

anikom15/docs/blob/patch-1/docs/development/shader/slang-shaders.md

# Developing Slang Shaders

## Target shader languages
 - Vulkan
 - GL 2.x (legacy desktop)
 - GL 3.x+ (modern desktop)
 - GLES2 (legacy mobile)
 - GLES3 (modern mobile)
 - HLSL
 - Metal

**Design principle: Avoid mandating high-level features which do not work for GLES2.**

RetroArch runs on GL, GL2, and GLES2. GL and GL2 are only relevant from a legacy standpoint, but GLES2 a relevant target platform today and having GLES2 compatibility makes GL2 very easy. We therefore avoid a design which deliberately ruins GLES2 compatibility.

However, we also do not want to artificially limit ourselves to shader features which are only available in GLES2. There are many shader builtins, for example, which only work in GLES3/GL3 and we should not hold back support in these cases.

## Why a new spec?

The previous RetroArch shader subsystem in RetroArch is quite mature with a large body of shaders written for it. While it has served us well, it was not forward-compatible.

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Eventually I hope to get a revision pulled, but want to get visibility since seems most of the shader developers congregate here and maybe don’t follow this doc GitHub. If you have any suggestions or find anything wrong/confusing I’d love to hear about it.

Here is the pull request as well if you want to look at commits:

thingsiplay · 26 February 2026 15:09

I just want to say, this is actually one of the best use cases for an Ai tool I have seen.

hunterk · 26 February 2026 23:35

I only had a chance to read over less than 1/4th of it last night, but what I read looked good.

anikom15 · 3 March 2026 03:22

The main thing I still need to add is how to do HDR.

kokoko3k · 4 March 2026 12:16

Please, also check here:

github.com

libretro/slang-shaders/blob/master/README.md

# Vulkan GLSL RetroArch shader system

This document is a draft of RetroArch's new GPU shader system.
It will outline the features in the new shader subsystem and describe details for how it will work in practice.

In addition this document will contain various musings on why certain design choices are made and which compromised have been made to arrive at the conclusion. This is mostly for discussing and deliberation while the new system is under development.

## Introduction

### Target shader languages
 - Vulkan
 - GL 2.x (legacy desktop)
 - GL 3.x+ (modern desktop)
 - GLES2 (legacy mobile)
 - GLES3 (modern mobile)
 - (HLSL, potentially)
 - (Metal, potentially)

RetroArch is still expected to run on GLES2 and GL2 systems.
GL2 is mostly not relevant any longer, but GLES2 is certainly a very relevant platform still and having GLES2 compatibility makes GL2 very easy.

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I don’t know why, but somehow files differ, and the latter has more informations about uniforms, maybe it’s more up to date.

anikom15 · 26 March 2026 22:34

I was able to integrate the extra stuff in the README and add a section on HDR programming techniques. I will update the branch later. I believe it is ready to merge, but may wait until HDR updates are solidified so I can’t include the actual uniforms that will be available in next release.