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Comment by ivars | Hacker News Reader

How did they managed to pull this off so quickly? Given how long WebGPU native is in development and still not finalized, you would think it will take SDL GPU API even longer because it supports more platforms.

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The reason WebGPU took so long was that they decided to write their own shading language instead of using SPIR-V. SDL didn't make that mistake, you bring your own shader compilers and translation tools.

There is a sister project for a cross-platform shading language [1] and another for translating existing ones between each other [2] , but they get done when they get done, and the rest of the API doesn't have to wait for them.

WebGPU was made by a committee of vendors and language-lawyers (standards-lawyers?) with politics and bureaucracy, and it shows. SDL_GPU is made by game developers who value pragmatism above all (and often are looked down upon from the ivory tower because of that).

[1]: https://github.com/libsdl-org/SDL_shader_tools [2]: https://github.com/flibitijibibo/SDL_gpu_shadercross

Yeah, legal strikes again. Unfortunately SPIR-V was never going to be an option for WebGPU, because Apple refuses to use any Khronos projects due to a confidential legal dispute between them.[0] If WebGPU used SPIR-V, it just wouldn't be available in Safari.

See also: Not supporting Vulkan or OpenXR at all, using USD instead of glTF for AR content even though it's less well suited for the task, etc. (Well, they probably don't mind that it helps maintain the walled garden either... There's more than one reason for everything)

0: https://docs.google.com/document/d/1F6ns6I3zs-2JL_dT9hOkX_25...

# Attendance

## Khronos

Neil Trevett

## Apple

Dean Jackson Myles C. Maxfield Robin Morisset Maciej Stachowiak Saam Barati

## Google

Austin Eng Corentin Wallez Dan Sinclair David Neto James Darpinian Kai Ninomiya Ken Russell Shrek Shao Ryan Harrison

## Intel

Yunchao He

## Mozilla

Dzmitry Malyshau

## W3C

François Daoust Dominique Hazael-Massieux

## Timo de Kort [sic?]

———

I get that Apple/Google have significantly more resources than most organizations on the planet but if these demographics are representative of other (web) standards committees that’s depressing.

I don't think that's accurate. Creating a shading language is obviously a huge effort, but there were already years of effort put into WebGPU as well as implementations/games building on top of the work-in-progress specification before the shading language decision was made (implementations at the time accepted SPIR-V).

The PoC was made in 2016, the work started in 2017, but the first spec draft was released on 18 May 2021. [1] This first draft already contained references to WGSL. There is no reference to SPIR-V.

Why did it take this long to release the first draft? Compare it to SDL_GPU timeline, start to finish in 6 months. Well, because the yak shaving on WGSL had already begun, and was eating up all the time.

[1]: https://www.w3.org/TR/2021/WD-webgpu-20210518/

SPIR-V was never in the specification, but both wgpu and Dawn used SPIR-V in the meantime until a shading language decision was made.

Sure, but that proves my point. They took so long to decide upon the shading language that implementations had to erect a separate scaffolding just to be able to test things out.

Scaffolding wasn’t a problem at all. Both used SPIRV-Cross for shader conversions at the time and focused on implementing the rest of the API. The shading language barely matters to the rest of the implementation. You can still use SPIR-V with wgpu on its Vulkan backend today for example.

The core contributors of the SDL3 GPU project have experience with two cross-platform (PC + consoles) GPU abstraction layers, FNA3D and Refresh, which provided a lot of knowledge and existing open source code to use as a springboard to assemble this quickly with high quality.

No committee and motivated devs that need the result for their projects. Especially the FNA folks.

Also tbf, the WebGPU peeps did a lot of investigations for what is the actual set of common and web-safe features across D3D, Vulkan and Metal, and all those investigation results are in the open.

In that sense the WebGPU project is an extremely valuable resource for other wrapper APIs, and saves those other APIs a ton of time.

Yeah. SDL went the path of "wrap native APIs". WebGPU went the path of "exactly what level of floating point precision can we guarantee across all APIs" along with "how do we prevent absolutely all invalid behavior at runtime, e.g. out of bounds accesses in shaders, non-dynamically uniform control flow at invalid times, indirect draws that bypass the given limits, preventing too-large shaders that would kill shader compilers, etc".

WebGPU spends a _lot_ of time investigating buggy driver behavior and trying to make things spec-conformant across a lot of disparate and frankly janky platforms. There's a big difference between writing an RHI, and writing a _spec_.

Simple: SDL GPU left out the rest of the owl (translating shaders from a common format to API-specific intermediates).

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