SDL3 is still in preview, but the new GPU API is now merged into the main branch while SDL3 maintainers apply some final tweaks.
As far as I understand: the new GPU API is notable because it should allow writing graphics code & shaders once and have it all work cross-platform (including on consoles) with minimal hassle - and previously that required Unity or Unreal, or your own custom solution.
WebGPU/WGSL is a similar "cross-platform graphics stack" effort but as far as I know nobody has written console backends for it. (Meanwhile the SDL3 GPU API currently doesn't seem to support WebGPU as a backend.)
Compared to libraries like bgfx and sokol at least, I think there are two key differences.
1) SDL_gpu is a pure C library, heavily focused on extreme portability and no depedencies. And somehow it's also an order of magnitude less code than the other options. Or at least this is a difference from bgfx, maybe not so much sokol_gfx.
2) The SDL_gpu approach is a bit lower level. It exposes primitives like command buffers directly to your application (so you can more easily reason about multi-threading), and your software allocates transfer buffers, fills them with data, and kicks off a transfer to GPU memory explicitly rather than this happening behind the scenes. It also spawns no threads - it only takes action in response to function calls. It does take care of hard things such as getting barriers right, and provides the GPU memory allocator, so it is still substantially easier to use than something like Vulkan. But in SDL_gpu it is extremely obvious to see the data movements between CPU and GPU (and memory copies within the CPU), and to observe the asynchronous nature of the GPU work. I suspect the end result of this will be that people write far more efficient renderers on top of SDL_gpu than they would have on other APIs.
I previously integrated bgfx [1], which allows you to write graphics code and shaders once and supports consoles, with SDL2 stack and Swift [2]. It was quite a nice experience, especially for someone who had never worked with any of these tools before. I'm excited for SDL3 as it introduces console abstractions, eliminating the need for additional dependencies for the GPU API. Moreover, Godot officially supports the Steam Deck, and hopefully, more consoles will be supported in the future. On a related note, Miguel de Icaza is advocating for Swift adoption in Godot, and he is working on porting the editor to SwiftUI on iPad. It is interesting to see the progress [3].
Worth noting Godot also has cross platform shaders. Its GDShader language is based heavily on OpenGL shader language though not a 1:1 copy and gets compiled for the target platform. Though for PS5 and XBox you have to work with a 3rd party (Someone released the Nintendo build for anyone who's signed the Nintendo NDA).
The old SDL 2D API was not powerful enough. It was conceived in the rectangle sprite blitting days, when video hardware was designed very differently and had drastically different performance characteristics. If you wanted anything more, OpenGL used to be 'the best practice'. But today, the landscape competes between Vulkan, Metal, and Direct3D, and hardware is centered around batching and shaders. Trying to target OpenGL is more difficult because OpenGL fragmented between GL vs. GLES and platform support for OpenGL varies (e.g. Apple stopped updating GL after 4.1).
A good example demonstrating where the old SDL 2D API is too limited is with the 2D immediate mode GUI library, Nuklear. It has a few simple API stubs to fill in so it can be adapted to work with any graphics system. But for performance, it wants to batch submit all the vertices (triangle strip). But SDL's old API didn't support anything like that.
The reluctance was the SDL maintainers didn't want to create a monster and couldn't decide where to draw the line, so the line was held at the old 2D API. Then a few years ago, a user successfully changed the maintainers' minds after writing a demonstration showing how much could be achieved by just adding a simple batching API to SDL 2D. So that shifted the mindset and led to this current effort. I have not closely followed the development, but I think it still aims to be a simple API, and you will still be encouraged to pick a full blown 3D API if you go beyond 2D needs. But you no longer should need to go to one of the other APIs to do 2D things in modern ways on modern hardware.
SDL provides various "backend agnostic" APIs for a variety of needs, including window creation, input (with a gamepad abstraction), audio, system stuff (e.g. threads), etc so that programs written against SDL can work on a variety of systems - and if linked against it dynamically (or using the "static linking but with a dynamic override" that allows a statically linked version to use a newer dynamic version of the library) can use newer/better stuff (which is sometimes needed, e.g. some older gaming using old version of SDL1.x need the DLL/.so replaced to a new version to work on new OSes, especially on Linux).
Exposing a modern (in the sense of how self-proclaimed modern APIs like Vulkan, D3D12 and Metal work) GPU API that lets applications written against it to work with various backends (D3D11, D3D12, Vulkan, Metal, whatever Switch and PS5 uses, etc) fits perfectly with what SDL already does for every other aspect of making a game/game engine/framework/etc.
As if it was "needed", it was needed as much as any other of SDL's "subsystems": strictly speaking, not really as you could use some other library (but that could be said for SDL itself) but from the perspective of what the SDL wants to provide (an API to target so you wont have to target each underlying API separately) it was needed for the sake of completeness (previously OpenGL was used for this task if you wanted 3D graphics but that was when OpenGL was practically universally available for the platforms SDL itself officially supported - but nowadays this is not the case).
While WebGPU isn't a bad API, it also isn't exactly the '3D API to end all 3D APIs'.
WebGPU has a couple of design decisions which were necessary to support Vulkan on mobile devices, which make it a very rigid API and even (desktop) Vulkan is moving away from that rigid programming model, while WebGPU won't be able to adapt so quickly because it still needs to support outdated mobile GPUs across all operating systems.
One important point I haven't seen mentioned yet is that SDL is the defacto minimal compatibility layer on Linux for writing a windowed 'game-y' application if you don't want to directly wrestle with X11, Wayland, GTK or KDE.
The more the merrier if you ask me. Eventually one will win but we need more experimentation in this space. The existing GPU APIs are too hard to use and/or vendor-specific.
WebGPU would be alot more useful if it hadn't gone with such a needlessly different shader language syntax, makes it much harder to have any single src between the C++ and it.
This rubs me the wrong way. Resource renaming is a high level concept, which was one of the features of OpenGL that all the modern APIs have successfully dropped. A modern low level GPU API should not do that.
It's exciting to see how this all shakes out. Hopefully we end up with more options for building custom game engines and apps.
I've been going down the Vulkan rabbit hole. It's been fun/enlightening to learn, but the nature of Vulkan makes progress feel slow. I think if SDL3 were available when I started, I would have happily went that route and have more to show for the amount of time I've invested.
Time will tell if this API is usable. In particular, the way resource synchronization works, and object renaming.
Time will tell if it will perform better than WebGPU or other abstractions.
Time will tell if it remains small in the presence of driver bugs that need working around…
I’m also sceptical about their new bytecode for a shading language. Parsing shaders at runtime was not a concern with WebGPU - it’s very fast. Even producing native shaders is fast [1]. It’s the pipeline creation that’s slow, and this bytecode wouldn’t help here.
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.
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).
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)
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 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.
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.
Bravo, thanks! Since I'll be targeting modern HLSL, your backend is the one I'll be using to begin with. Hopefully DXC produces decent SPIR-V at the end.
I might try this out.
SDL I have found to be high quality software - compiles fast, compiles easily on multiple platforms, always works. So I have some hopes for this new API.
When I went looking for a cross-platform gaming library, SDL and its API struck the right balance for me. I just wanted a C (++) library I could call to create windows and graphical contexts — a fast sprite rendering framework. I didn't need a whole IDE or a bloated library, didn't want to learn a new language, etc.
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As far as I understand: the new GPU API is notable because it should allow writing graphics code & shaders once and have it all work cross-platform (including on consoles) with minimal hassle - and previously that required Unity or Unreal, or your own custom solution.
WebGPU/WGSL is a similar "cross-platform graphics stack" effort but as far as I know nobody has written console backends for it. (Meanwhile the SDL3 GPU API currently doesn't seem to support WebGPU as a backend.)
1) SDL_gpu is a pure C library, heavily focused on extreme portability and no depedencies. And somehow it's also an order of magnitude less code than the other options. Or at least this is a difference from bgfx, maybe not so much sokol_gfx.
2) The SDL_gpu approach is a bit lower level. It exposes primitives like command buffers directly to your application (so you can more easily reason about multi-threading), and your software allocates transfer buffers, fills them with data, and kicks off a transfer to GPU memory explicitly rather than this happening behind the scenes. It also spawns no threads - it only takes action in response to function calls. It does take care of hard things such as getting barriers right, and provides the GPU memory allocator, so it is still substantially easier to use than something like Vulkan. But in SDL_gpu it is extremely obvious to see the data movements between CPU and GPU (and memory copies within the CPU), and to observe the asynchronous nature of the GPU work. I suspect the end result of this will be that people write far more efficient renderers on top of SDL_gpu than they would have on other APIs.
https://github.com/NVIDIAGameWorks/nvrhi
[1] https://bkaradzic.github.io/bgfx/overview.html
[2] https://github.com/bgbernovici/myndsmith
[3] https://blog.la-terminal.net/xogot-code-editing/
A good example demonstrating where the old SDL 2D API is too limited is with the 2D immediate mode GUI library, Nuklear. It has a few simple API stubs to fill in so it can be adapted to work with any graphics system. But for performance, it wants to batch submit all the vertices (triangle strip). But SDL's old API didn't support anything like that.
The reluctance was the SDL maintainers didn't want to create a monster and couldn't decide where to draw the line, so the line was held at the old 2D API. Then a few years ago, a user successfully changed the maintainers' minds after writing a demonstration showing how much could be achieved by just adding a simple batching API to SDL 2D. So that shifted the mindset and led to this current effort. I have not closely followed the development, but I think it still aims to be a simple API, and you will still be encouraged to pick a full blown 3D API if you go beyond 2D needs. But you no longer should need to go to one of the other APIs to do 2D things in modern ways on modern hardware.
Exposing a modern (in the sense of how self-proclaimed modern APIs like Vulkan, D3D12 and Metal work) GPU API that lets applications written against it to work with various backends (D3D11, D3D12, Vulkan, Metal, whatever Switch and PS5 uses, etc) fits perfectly with what SDL already does for every other aspect of making a game/game engine/framework/etc.
As if it was "needed", it was needed as much as any other of SDL's "subsystems": strictly speaking, not really as you could use some other library (but that could be said for SDL itself) but from the perspective of what the SDL wants to provide (an API to target so you wont have to target each underlying API separately) it was needed for the sake of completeness (previously OpenGL was used for this task if you wanted 3D graphics but that was when OpenGL was practically universally available for the platforms SDL itself officially supported - but nowadays this is not the case).
WebGPU has a couple of design decisions which were necessary to support Vulkan on mobile devices, which make it a very rigid API and even (desktop) Vulkan is moving away from that rigid programming model, while WebGPU won't be able to adapt so quickly because it still needs to support outdated mobile GPUs across all operating systems.
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I've been going down the Vulkan rabbit hole. It's been fun/enlightening to learn, but the nature of Vulkan makes progress feel slow. I think if SDL3 were available when I started, I would have happily went that route and have more to show for the amount of time I've invested.
I’m also sceptical about their new bytecode for a shading language. Parsing shaders at runtime was not a concern with WebGPU - it’s very fast. Even producing native shaders is fast [1]. It’s the pipeline creation that’s slow, and this bytecode wouldn’t help here.
[1] http://kvark.github.io/naga/shader/2022/02/17/shader-transla...
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
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...
In that sense the WebGPU project is an extremely valuable resource for other wrapper APIs, and saves those other APIs a ton of time.
When I went looking for a cross-platform gaming library, SDL and its API struck the right balance for me. I just wanted a C (++) library I could call to create windows and graphical contexts — a fast sprite rendering framework. I didn't need a whole IDE or a bloated library, didn't want to learn a new language, etc.