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Comment by throwaway34241 | Hacker News Reader

Some context: browser vendors are working on a successor to WebGL, and there's been a debate over what shading language to use.

A text based language would be easier for beginners (since they wouldn't need to install a separate shader compiler) and would avoid sites that need dynamic shaders having to download and run a shader compiler in the browser.

Using SPIR-V bytecode would benefit from a large amount of work put into an existing standard and an open source compiler ecosystem that many companies are already using.

It looks like a decision has been made to accept a text based language, but one that is defined based on SPIR-V semantics and is easily convertible back and forth from SPIR-V. This seems like a great trade off since if it works out it should have the main advantages of both approaches.

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> A text based language would be easier for beginners (since they wouldn't need to install a separate shader compiler) and would avoid sites that need dynamic shaders having to download and run a shader compiler in the browser.

That is more or less the official rationale, but it's pretty clear that the real reason is that Apple is organizationally opposed to SPIR-V (and Khronos generally). This is a tough needle to thread, so I'm glad forward progress is being made.

I strongly favor sticking to DRM-free text-based formats for the web. I remember learning a lot just from looking at the HTML and JS sources from web pages. It's been a great boon for the web up until now. Besides lots of apps already ship shaders as text. They get dynamically compiled and cached, just like JS does. Being text-based hasn't stopped JS from greatly improving performance.

Khronos sat on their hands for years and only moved after Apple shipped Metal and AMD dumped Mantle in their laps (I'll note that Metal came first). SPIR-V is not the be-all end-all of shader programming. Personally I don't believe we should accept some lowest-common-denominator that puts the future of GPU development in the hands of an organization with the track record Khronos has wrt managing OpenGL. That goes double for the future of WebGPU. However I recognize those are just personal opinions and reasonable people may disagree.

To those offering opinions here: If you've never written a renderer or shader can I suggest you write a toy project using both then see if you still have the same opinion?

The problem with the view-source argument is that source is often minified these days, so you need a decompiler of some sort to go from the bits on the wire to something human-readable no matter what. A pretty-printer can sometimes be simpler than an IR decompiler, but often not really.

I purposefully don't minify the source on my personal website, so people can still learn from inspecting it, if they'd like to.

Regardless of Apple’s motivations those still are real benefits, I think at least one major WebGL framework uses dynamic shader generation and was looking at going the bundled-shader-compiler route. Hopefully this approach cuts back on the projects that find it necessary to do that and encourages faster adoption from WebGL.

If you're willing to do dynamic shader generation as text, you can generate shader bytecode. The real question is which of the two options produces more performant shaders and faster compile times, since naively-generated shader bytecode isn't being optimized like your text is. If you care about compile times text-based can be a lot worse (this matters for the Dolphin emulator, for example)

That is correct, in theory, but there is a large gap between theory and practice. How practical would it be for, say Three.JS to generate shader bytecode? Would it need to depend on a sophisticated WASM module that allows to build such bytecode? Who is going to build that?

Google has spent a lot of effort trying to answer these questions, and they got close, but in the end the text-based solution prevailed. In part, because it was easy to agree on for all parties.

Do you not expect GLSL -> WGSL compilers in actual practice? I don't think anybody using Three.JS today would switch to writing WGSL unless they could also ingest it on WebGL.

In one of the futures, our shader translation infrastructure will support GLSL input and produce WGSL output :)

That’s true, even if the semantics are the same (and parsing time isn’t a big factor) the assumptions for what optimizations have been applied to bytecode might be different. I remember seeing in one of the meeting notes that they didn’t expect browsers to end up making assumptions about the optimization level of the SPIR-V they ingest anyway but I don’t remember the specific rationale for that.

There’s of course also the time for the SPIR-V -> gpu native step. It would be nice if they could just cache that and skip the whole process most of the time.

Indeed. A text-based language makes no sense in 2020. WASM already took the approach of going binary-first.

If you want live-tweakable or generated webgpu shaders, which will be useful in many applications text based is much better as no complex tooling is required.

You could still build something like Shadertoy if the WebGPU shaders internally used a binary format. You would just need to have a JS or WASM library that compiles text shaders into the binary format. It's not that difficult to do, and it can absolutely run in the browser.

There's a SPIR-V text representation that maps directly to the binary representation. Even if it was given a binary, the browser could display the equivalent text representation.

Useful to what applications ? Even writing modern JS requires a compiler stack, adding a shading language would be a matter of writing a webpack loader.

As an example, ShaderToy (and ShaderGif which I built) compile shaders directly in the browser.

As they have already told you, shaders being in binary or text form is orthogonal to making a tool like ShaderToy.

However, binary form is way more compact for transmission, storage and performance. Almost nobody will use the text form except developers.

> However, binary form is way more compact

That’s what I might expect too, so I was surprised to find out that SPIR-V is usually substantially larger than text based shaders. It also doesn’t seem to compress optimally using standard algorithms. [1]

[1] https://aras-p.info/blog/2016/09/13/Shader-Compression-Some-...

The transmission/storage size of shaders isn't important. Textures and 3D models dominate in any non trivial project. Kind of like dieting by trimming your toenails.

That’s maybe true for current 3D graphics heavy projects, but is not necessarily true for any arbitrary future use of GPU compute.

GPUs are machines for crunching data, be it graphics or NNs. I can't think of many use case where that isn't true.

Also if you anticipate the GPU being used as an accelerator, that is all the more reason to use a text based format because it allows for easy code generation.

You are wrong. Many projects use GPUs without big datasets. See ShaderToy, for instance: a lot of computation, almost no input data. Many other games, too: they may use the GPU for rendering fast yet have say 50 MiB of textures and assets only.

If you think of AAA games, ML and whatnot, of course. But I doubt anybody will use WebGPU for those, to be honest.

50MB of textures is a lot compared to shader source code size, which will be in the kilobytes for such a small project.

The same with shadertoy, the storage or transmission of a shadertoy shader is never going to be significant compared to all the assets on the page.

The contention was that a binary representation is necessary to save space for storage or transmission. It just isn't.

I'm sure there will be JS libraries that can compile them in the browser - a minor inconvenience for those apps.

Why does it require a compiler stack?

If you want to use React with JSX then you must add babel to your project.

I think the counter-argument to "but WASM?!" is that on the Web you still can use text to describe the behavior. WASM is optional. At the same time, if WebGPU picked SPIR-V binary, it wouldn't have a built-in way of programming without dependencies inside a browser.

I'm not quite sure what you're saying. WASM is optional in the same way that WebGPU is optional. They both allow you to invoke code written in another language.

There's not really a good way of writing WASM without dependencies inside a browser.

What I wanted to say is that we as a group want people to be able to use the browser and nothing else to develop WebGPU if they want.

WASM by itself doesn't provide new APIs, it's still just a different way to expose the Web platform. So WASM being optional doesn't limit anybody in what they can do. Having WebGPU optional does limit what you can do on the web. We want WebGPU to be available in a wide sense (accessibility, dependencies, portability, everthing).

Being able to develop with the browser has nothing to do with WebGPU being binary or text.

It seems you speak with "we", as if you were part of the committee? If that is a yes: how can we become part of that committee to amend this mistake? Who has voting rights?

How are you suggesting to write shaders in the browser if they are expected to be in a binary form?

WebGPU community group is open to anyone interested: https://www.w3.org/community/gpu/

We can compile and run c++ code in a browser with WASM versions of clang, why would it be any issue to compile glsl / any other language to spir-v ? That's already what almost everyone is doing with spirv-cross / shaderconductor on the desktop

WebGPU doesn’t provide new APIs in the same sense that WASM doesn’t provide new APIs, they just provide alternative APIs to accomplish the same tasks, but faster.

Anything you can do with WebGPU you could do in JavaScript, in the same sense that anything you can do with WASM you can do in JavaScript. The only difference is performance.

Is there really such a great need to make the lowest level shader API more accessible to beginners? You can always build things on top that make a low-level API more friendly, but you can never build something below the lowest available level (short of inventing a new standard). What kind of beginners are these that want to do low-level shader programming, but without any tooling? Don't web programmers already accept the use of heavyweight build tools even for their plan old ordinary Javascript?

My enthusiasm for seeing yet another GPU language is very restricted. I simply cannot see the rational arguments in favour of this design. We were so close to having a standard IR for this stuff.

I think the goal here is for the semantics to basically be SPIR-V, and for people using SPIR-V toolchains to be able to expect WebGPU platforms with a Vulkan backend to execute basically the same SPIR-V after the conversions to/from text.

Knowing Vulkan, WebGL, and OpenGL and working a bit with some of those technologies while hobbying the others, WebGPU will take about a decade to be fully adopted, and even then, only by a fraction of companies that are willing to spend manpower resources into developing something interfacing low level graphics directly.

WebGPU is important for game engines, currently it is missing a lot of features so you can't write the shaders you want.

I agree. Originally SPIR (without a V) was just a 1:1 copy of LLVM IR with no commitment to backwards compatibility. Every time LLVM IR changed SPIR had to change as well. This lead to two major versions of SPIR. Clearly this is not a sustainable solution. Implementing several versions of the same IR is a huge support burden for almost no benefit. Now we have the successor SPIR-V which is no longer tied to LLVM IR. Anyone can implement SPIR-V support without LLVM. There is no excuse to not use it. It's basically the same story with WebAssembly. LLVM IR wasn't good enough so someone had to actually do it properly this time.

That's because there is no rational reason. The reason this is at it all an issue is because Apple put their foot down and flat out refused to implement SPIR-V.

They also refused to implement WebP support. If they can't get their act together I'll still get my revenge by using a polyfill that decodes WebP images with Javascript (goodbye battery life!).

I dont want an Google Image format so I am glad they dont support WebP. I much rather they support JPEG XL.

The willingness of the various web consortiums to bend over backwards for individual corporations has got to end. It's making the web worse, not better.

> browser vendors are working on a successor to WebGL

Interesting, what's the successor? I haven't heard of this.

WebGPU

https://webkit.org/blog/9528/webgpu-and-wsl-in-safari/

https://developers.google.com/web/updates/2019/08/get-starte...

https://doc.babylonjs.com/extensions/webgpu

Basically, the Web version of Metal, DirectX12, Vulkan, LibGNM, NVN.

> Some context: browser vendors are working on a successor to WebGL

What's wrong with WebGL?

It has an outdated programming model, no multi-threading, no compute (portably supported everywhere), limited access to the hardware, etc

It is stuck in a OpenGL ES 3.0 subset.

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