Better « How to write shaders » guide

[hadronized]

Hello!

I’m looking for a way to write my shaders using rust-gpu, and I realized it’s not as easy as I thought it would be. The main issue I have is the guide that doesn’t really go deep in details on how to setup the various crates, and the toolchain.

From my understanding, given what cargo-gpu does, it should be possible to compile the shader codes without impacting the toolchain of the main project, even though it depends on the SPIR-V builder.

Also, I saw there was a way to bypass the toolchain check, but I haven’t been successful at it so far (it keeps complaining about the wrong toolchain being used).

Thanks in advance!

[schell]

Hi @hadronized :)

I haven't started on the cargo-gpu manual yet, but if you use the version that's on main as of this reply, you should be able to run cargo gpu build --shader-crate path/to/your/crate and it should determine and install the necessary toolchain for you, as well as compiling the rustc backend that does SPIR-V codegen and invoking cargo with the necessary args.

If you run into any trouble please open a ticket at the cargo-gpu repo.

[hadronized]

Cool, thanks for the fast reply. I think I struggle the most with is the crate separation that is required because of all the toolchain setup. I’m not sure whether it’s the tooling that’s hard to work with, or whether it’s just me not used to it.

I’ll play along with it, thanks!

[schell]

Oh, you don't have to separate your crate into GPU and CPU crates! You can combine them, but when compilingfor GPU the crate must be no_std. I use this annotation in my own project: #![cfg_attr(target_arch = "spirv", no_std)] (along with a bunch of others). This will allow you to have CPU code in your shader crate, so long as it is feature/target_arch gated. You can peruse my project at https://github.com/schell/renderling if you'd like to see how I set this up.

[hadronized]

Ah that’s cool! I’m trying out to invoke cargo-gpu in my build.rs, is there any recommended way to do that besides just using Command::new()?

[schell]

In my own project I have building shaders as an explicit step that I have to invoke on the command line, because compile times can be quite long, and I often don't want to compile my shaders every time a file changes.

But if you do want to do that, I think Command::new() (or something similar) is probably your best bet. cargo-gpu is not set up to be used as a library. At least not yet.