Comment by raphlinus | Hacker News Reader

Comment by raphlinus | Hacker News Reader

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This is still in transition, and the full story is complicated.

The official shader language for WebGPU is WGSL, and that will almost certainly be the only language supported for web deployment. Originally this was going to be a textual representation that had exactly the same semantics ("bijective") as SPIR-V, but that's been diverging a bit[1]. Only very recently have atomics been added to the spec, and implementations are still catching up.

Because WGSL is still under construction, for native deployment, wgpu supports SPIR-V shaders as well. On Vulkan, those are passed pretty much straight through to the GPU driver (with some validation). On DX12 and Metal, those are translated into HLSL and MSL, respectively. Until recently, in wgpu, all those translations were handled by spirv-cross. More recently, the new naga crate is doing those translations. Again, this is under construction and not everything works yet.

[1]: https://kvark.github.io/spirv/2021/05/01/spirv-horrors.html

From [1]:

> When writing SPIR-V, you can’t have two integer types of the same width. Or two texture types that match. All non-composite types have to be unique for some reason. We don’t have this restriction in Naga IR, it just doesn’t seem to make any sense. For example, what if I’m writing a shader, and I basically want to use the same “int32” type for both indices and lengths. I may want to name these types differently

This doesn't really make sense for IR. IR is not meant to be human writeable. It's meant to be generated by a compiler. So, having a one to one mapping between concept and name in the IR is a feature, not a bug.

Honestly, WGSL just repeats the JavaScript mistake: where we should have started with something like WASM instead of JavaScript. And JS could have been just one of the many languages that targeted WASM.

We were this close to not repeating this mistake by adopting an IR language (SPIR-V) for WebGPU, but then that got abandoned mostly for political reasons. Too bad. Now we get to write transpilers and hacks for decades to come, just like web people have been trying to paper over JS problems for decades.

> This doesn't really make sense for IR. IR is not meant to be human writeable. It's meant to be generated by a compiler. So, having a one to one mapping between concept and name in the IR is a feature, not a bug.

Do you consider the name for a type to be a part of the concept? SPIR-V doesn't. Overall, if you wanted one-to-one mapping, at least that would be consistent. But SPIR-V decided to require this only for simple types, while you can still have duplicate composite types.

> Honestly, WGSL just repeats the JavaScript mistake: where we should have started with something like WASM instead of JavaScript. And JS could have been just one of the many languages that targeted WASM.

We don't know if Web would be nearly as successful if it started with WASM instead of JS. The ability to just open a text editor and make a web page has served well in the early days.

> We were this close to not repeating this mistake by adopting an IR language (SPIR-V) for WebGPU, but then that got abandoned mostly for political reasons.

Look at the situation today: the very same people who were rooting for SPIR-V are currently introducing features the diverge WGSL away from SPIR-V, further and further. It's quite telling, I think. The moral of the story is: regardless of reasons (which we can argue a ton), WG members admit that what we ideally need is not SPIR-V, and this is supported by the way WGSL is shaping.

> We don't know if Web would be nearly as successful if it started with WASM instead of JS. The ability to just open a text editor and make a web page has served well in the early days.

And you would be able to do that just fine. All you'd need to do is include the JS compiler (helpfully hosted at http://cdn.google.com/ecmascript-2015.wasm) in the <head> of the HTML file's script tag, open a text editor and type away. Or, you know, include a more sane language like typescript, or python. Heck even lisp if you're so inclined. Or, and this is like totally crazy, but say you need performance, and want tight control over memory layout and allocations, then go for C or rust! Oh and no need to minify your JS. Just ship the WASM precompiled. Save on browser compilation time and network bytes at the same time. So long as you generate WASM that the browser understands use whatever lang makes you happy. Type it right into a text editor and include the compiler in the head of the HTML. Easy peasy.

It's without question that JS has held back web development for decades. Of course, people didn't know any better back then, and really JS was added as almost an afterthought, so we can't really blame them for getting it wrong.

We do know better now though. And still we get WGSL. Looking forward to 2041, when we finally get WGASM. The hottest new thing in web gpu technologies.

We will be back at native apps with networking protocols by then. :)

Welcome to the design by comittee APIs.

In restrospective I wasted a couple of years of my life beting on OpenGL, and keep seeing the same errors in all Khronos related APIs.

It is not only WebGPU, check how many extensions Vulkan has already.

Then there is OpeCL C++ versus SYSCL, OpenCL 3.0 is actually 1.2 rebooted,...

I see. Thank you for the detailed information. I will read the linked content.

I don't know if this is a good place to ask. But I was interested in wgpu because of the interest in building a cross-platform non-web UI library. I read a few of your articles and also looked at druid. I am pretty new to it and there seems to be no books on this topic. Do you have any recommendations?

Yes: don't. It's very hard.

More seriously. There is very good reason to be encouraged about wgpu as a cross-platform low-level GPU drawing interface for UI work. There are already successful UI toolkits using it, of which probably the most impressive is iced.

For 2D graphics in general, a good starting point is Diego Nehab's 2D graphics course. It has links to a bunch of resources including papers on GPU rendering.

Of course, I'm working on my own stuff, which in time I hope will become a very strong foundation for building things such as UI toolkits, but it's not ready yet, and of course you're already aware of it.

[1]: http://w3.impa.br/~diego/teaching/vg/

Saved in my note, much appreciated.

Yes, I agree building a UI library from scratch is hard and probably not worthy doing (too many people tried and gave up in the middle; probably better to channel that enthusiasm on improving existing ones). I should state that more clearly. I was looking at something more modest, like a canvas implementation based on wgpu that enables others to build their UI libraries on top.

I guess it would be something like Skia, but it also sounds like a tremendous effort, and I could probably just use Skia instead. However, I guess I am not going to match what Skia has (maybe what HTML canvas has is enough?). Also, I have played with skia-safe crate but I personally feel the dev experience could be better (not to blame skia-safe, it's wonderful and even provides a build process that automatically downloads a precompiled skia library).

Thanks for pointing out Iced. I didn't know they are using wgpu under the hood. I will take a good look at their code. I have been reading nannou's code to learn how to work with wgpu. If we skip my last paragraph, I think building a UI library on top of nannou is pretty doable.

[1]: https://github.com/nannou-org/nannou

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