Shadertoys Ported to Rust GPU
41 comments
·April 12, 2025AndrewPGameDev
wyager
Had not heard of Slang, thanks for sharing.
It's interesting that Slang looks more like Rust than WGSL does, despite WGSL kind of being de facto "owned by" the Rust community.
pcwalton
Not sure why you think WGSL is owned by the Rust community--it's clearly owned by the W3C. (That's part of why it moves so slowly.) WESL [1] is the community-owned set of extensions to WGSL that, while incomplete, promises to move it much closer to Rust.
pjmlp
Not sure where you get that from, Slang is an evolution of HLSL with a bit of C# sprinkled on top.
Actually this is a divergence point with HLSL202x evolution, which aims to be more C++ like.
WGSL is the only shading language with Rust influence.
WithinReason
See slang it in action: https://shader-slang.org/slang-playground/
TinkersW
Slang is nice improvement on HLSL, but wish it was more like C++ and not C#(easier to share code).
LegNeato
I have a WIP naga backend that converts glsl and hlsl to rust-gpu shaders.
shadowgovt
So why Rust?
Rust is great for tracking the lifetime of long-lived resources, which everything in a shader isn't.
Apart from that, what makes Rust a good fit for this problem domain?
virtualritz
I think that if you have a game/DCC/whatever app you write in Rust, being able to also write any shaders it uses in Rust is simply nice.
And as an added benefit it means not adding another language to a project and all that comes with it for build system/CI. I.e. cargo takes care of everything. That alone is worth a lot IMHO.
Apart from that its not related to Rust. Just replace Rust with your fav. language and imagine you could also write shaders/GPU-targeted code in it. Isn't that desirable?
ghfhghg
Kind of and I've certainly used systems like that before but in practice it's not really a massive improvement. Sometimes it's even a tad annoying having another layer of indirection.
pornel
Lifetime tracking isn't just for safety or resource management. It also helps write correct code, especially parallel one where shared vs mutable matters.
Unit testing of shaders is usually a pain. Traditionally they're a black box without any assert() equivalent, and you can at best try to propagate NaN and generate magenta pixels on failure. Sharing Rust code lets you unit-test parts of it on the CPU.
Sharing of data structures between CPU and GPU is nice too. WGSL is superficially similar to Rust, but using plain WGSL requires maintaining bindings and struct layouts by hand, which is a chore.
For CUDA, the alternative is C++. On the upside that's the official first-class API for CUDA, but the downside is that it's C++. With Rust you don't have the legacy language cruft, nor busywork like header files or makefiles. You get working dependency management, and don't get caught in the unix vs Windows schism.
exDM69
> Traditionally they're a black box without any assert() equivalent
Thankfully these days we have printf in shaders that you can use for "asserts". You can detect if the shader printed anything and consider it a failure.
You can even add a conditional print in your pixel shader, run your app in renderdoc and find the pixel(s) that printed something. Once you find one, you can step through it in the shader debugger.
This seemingly simple feature is a huge time saver.
Const-me
> Sharing of data structures between CPU and GPU is nice too
How they did it? Hard to do because GPU hardware can convert data types on the fly, e.g. you can store bytes in VRAM, and convert them to 32-bit floats in [ 0 .. +1 ] in the shader. GPUs can do that for both inputs (loaded texture texels, loaded buffer elements, vertex attributes) and outputs (rendered pixels, stored UAV elements).
exDM69
If you are using plain buffers the GPU and the CPU access data pretty much exactly the same way. With scalar block layout all the alignments are pretty much the same too.
To get the format conversion stuff you talk about, you need to use images, vertex input or texel buffers and configure the format conversion explicitly.
It's a good question how much of these conversions are actually done by GPU hardware and how much of it is just software (which you could write yourself in a shader and get same perf). I have not seen an apples to apples benchmark about these format conversions.
pjmlp
Just as an example the way Vulkan lifetime work depending on the resource group and associated semaphores, doesn't fit neither with Rust affine types, nor with RAII, hence so many don't make use of the C++ RAII handles on the Vulkan SDK.
wyager
Rust's ecological niche, besides the affine types/lifetime stuff, is "borrow as much stuff as we can from Haskell/ML without dragging in a language runtime".
"Without dragging in a language runtime" happens to be a primary requirement for writing bare-metal code or writing GPU shaders.
So you have a language that does have a bunch of nice new features (ADTs, acceptably modern type system, etc.) and doesn't have any of the stuff that prevents you from compiling it to random bare-metal targets like GPUs or MMUless microcontrollers.
pjmlp
Basically slang, GLSL replacement, designed by NVidia and adopted by Khronos as industry standard.
shadowgovt
Update: thanks to everyone for the thoughtful comments on this.
I'm so in the weeds with dealing with GLSL these days that "What if you could use the same language to implement the CPU logic as the GPU logic" wasn't even a goal I could see. That's actually quite huge; my concerns around Rust were mostly that it's not a deeply simple language and so much of shader frameworks is code-that-writes-code, but it's simple enough that I think it could still be used in that space, while granting the advantages of not having to context-switch in and out of one's CPU-language while developing a shader.
This has promise!
xphos
I think being able to develop it is a testiment that rust makes embeddeding stuff like this much easier than other languages. Its also intergrated in a rust project so you might not want to hop to a new language to do some shader stuff quickly
thrance
Rust also has a great type system and zero-cost abstractions. Plus there's already cuda if you want to run C on the GPU.
marsven_422
[dead]
nefarious_ends
Anyone have recommendations for resources for learning to write shaders?
FjordWarden
I've always enjoyed watching The Art of Code[1], Freya[2] also has a good number of videos on it.
But that is just vertex shaders for things like Shadertoys.
There is much more to computer graphics or GPGPU than this though, Im still learning about that myself X).
[1] https://www.youtube.com/watch?v=eKtsY7hYTPg [2]https://www.youtube.com/watch?v=kfM-yu0iQBk
arjonagelhout
My experience with writing shaders (such as for physically based rendering) is that the shading languages (MSL, GLSL, HLSL) are easy to switch between. The hard part is understanding the physics and understanding how GPUs work internally.
My main approach to writing shaders is to look at existing programs (e.g. Blender) and see what techniques are in use. The Google Filament renderer documentation [0] is also really good when it comes to BDSF functions.
Some papers from Unreal Engine might also help, such as "Real Shading in Unreal Engine 4" [1]
[0] https://google.github.io/filament/Filament.md.html
[1] https://cdn2.unrealengine.com/Resources/files/2013SiggraphPr...
jms55
If you want to make nice looking materials and effects, you need a combination of good lighting (comes from the rendering engine, not the material), and artistic capabilities/talent. Art is a lot harder to teach than programming I feel, or at least I don't know how to teach it.
Programming the shaders themselves are pretty simple imo, they're just pure functions that return color data or triangle positions. The syntax might be a little different than you're used to depending on the shader language, but it should be easy enough to pick up in a day.
If you want to write compute shaders for computation, then it gets a lot more tricky and you need to spend some time learning about memory accesses, the underlying hardware, and profiling.
alook
The book of shaders is fantastic:
setr
FYI apparently the www.* link doesn't actually have the menu for some reason? It's just the world graphic and a blank menu bar.
You need to visit http://thebookofshaders.com/
hackyhacky
> While over-all better alternatives to both languages exist, none of them are in a place to replace *HLSL* or *GLSL*. Either because they are vendor locked, or because they don't support the traditional graphics pipeline. Examples of this include *CUDA* and *OpenCL*.
Are CUDA and OpenCL really "better alternatives" to HLSL and GLSL?
CUDA and OpenCL are compute languages; HLSL and GLSL and shader languages. And while one can theoretically do compute in a shader (and we used to!) or shaders in a compute language, I think it's dishonest to claim that CUDA is intended as an updated alternative to GLSL. It's simply apples and oranges.
pjmlp
OpenCL no one cares about.
CUDA yes, it is already being used in commercial visualisation products like OctaneRender, one of the most important tools in the VFX industry.
NVidia also has plenty of customers on OptiX.
GLSL is dead end, Khronos is on the record they aren't going to develop it further, even for Vulkan, HLSL and now slang, are the way forward.
HLSL due to its use in the games industry, slang due to being developed by NVIDIA and given to Khronos as GLSL replacement.
rand0m4r
> GLSL is dead end, Khronos is on the record they aren't going to develop it further, even for Vulkan, HLSL and now slang, are the way forward.
I've been seeing more comments like yours saying GLSL is a dead end, and it’s making me question whether I should keep learning it.
But at the same time, it’s still very accessible, well-documented, and used in OpenGL demos and educational content. Would you say there's still a case for GLSL in hobby projects, demoscene work, or rapid prototyping? Or is it really time to move on even in those contexts?
impure
This is big news. Shaders have been a pain to develop for in Unity. If I can program them in Rust, leveraging Rust's tooling and ecosystem, that would be huge.
tubs
I understand the sentiment but to be very pedantic most GPUs do not understand SPIRV, it’s the drivers that do.
ImHereToVote
I hate to be pedantic but drivers don't understand at all. The driver accepts and can execute SPIR-V bytecode.
null
tripplyons
Very exciting project! Does this work on M-series macs? I've had trouble running some shaders on my laptop before.
LegNeato
Yes. Under the hood it uses wgpu and naga, which translates the SPIR-V into metal so it runs iOS and macOS (on Linux and Windows it uses spirv on vulkan directly)
Jothamcloud
[flagged]
I've spent a little time in this space, and I'm not sure it's a good idea to write shaders in Rust, although it's probably better than GLSL or WGSL.
Let me start with the pros:
1. Don't have to learn 2 different languages
2. Modules, crates, and the easier ability to share code
3. Easier sharing between rust structs and shader code.
Now the cons, in comparison to Slang [1]
1. No autodiff mode 2. Strictly outputs SPIR-V, while Slang can do CPU, CUDA, Pytorch, Optix, and all the major graphics APIs
3. Less support - Slang is supported by the Khronos group, and Slang gets use at Nvidia, EA, and Valve.
4. Safety isn't very valuable, most GPU code does not use pointers (it's so rare it's considered a feature by Slang!)
5. slangc probably runs a lot faster than rustc (although I would like to see a benchmark.)
6. Worse debugging experience, slang has better interop with things like NSight Graphics, and their Shader Debugger. Slang recently got support in NSight graphics for shader profiling, for example.
7. Slang has support for reflection, and has a C++ api to directly output a JSON file that contains all the reflected aspects.This makes handling the movement between rust <-> gpu much easier. Also, the example shown on the website uses `bytemuck`, but `bytemuck` won't take into consideration the struct alignment rules[2] when using WebGPU. Instead, you have to use a crate like `encase`[3] to handle that. I'm not sure given the example on the website how it would work with WebGPU.
8. If you have pre-existing shaders in GLSL or HLSL, you can use slangc directly on them. No need to rewrite.
9. In reality, you may not have to learn 2 languages but you have to learn 2 different compute models (CPU vs GPU). This is actually a much harder issue, and AFAICT it is impossible to overcome with a different language. The problem is the programmer needs to understand how the platforms are different.
[1] https://shader-slang.org/ [2] https://webgpufundamentals.org/webgpu/lessons/resources/wgsl... WGSL struct alignment widget [3] https://github.com/teoxoy/encase