OpenGL support

[inodentry]

Wgpu now has a working OpenGL backend. I know bevy intends to support that, but it does not work yet.

Creating this issue to make it easier to track progress on that front.

[cart]

Yup just for some additional context, I upgraded bevy to use "git wgpu" here: https://github.com/cart/bevy/tree/upgrade-wgpu, but I get this error:

Probably somehow related to the fact that Bevy does some rendering stuff (like creating gpu resources) on other threads.

[cart]

Using schedule.run() (single threaded) instead of the parallel executor got me past the threading errors.

Then I hit an issue where wgpu didnt like that we use ceil() in sprite_sheet.vert:

Removing that unlocked a new error:

Which indicates that we're using an unsupported binding type:

@kvark I'm just pulling you in so you're aware of where we're at. I'm not asking you for anything 😄

[cart]

I pushed a new branch with the changes listed above: https://github.com/cart/bevy/tree/opengl-testing

[kvark]

It's too early for Bevy to play with our OpenGL backend. Let us at least get our own samples running first 😅

[agorgl]

Any updates on this? Today I tried and wgpu-rs examples work with latest gfx-backend-gl

[cart]

No updates yet. We're waiting on two things:

1. Someone to test that bevy master + wgpu-rs master + OpenGL work together / fix any bugs
2. Wgpu-rs to have a crates.io release with opengl support

[kvark]

wgpu-rs OpenGL support is now enabled on master but not ready for general consumption. At the very least we want to be running all of our own examples before recommending it. So far, it only runs a few examples.

[cart]

Makes sense to me. Definitely take your time / don't feel any pressure from our end 😄

[agorgl]

A little update on this:

Bevy now runs with latest wgpu-rs master + OpenGL, but:
a) OpenGL gfx backend does not support (nor will according to @kvark) multithreading usage
b) Even running with single_threaded_pool bevy has some asset loading/binding issues and a black window is displayed for example in the sprite sample

[windelbouwman]

This is cool! I'd like to try this out (since I do not have vulkan support).

My strategy was modifying crates/bevy_wgpu/Cargo.toml to contain this line:

wgpu = { git = "https://github.com/gfx-rs/wgpu-rs.git", branch = "master" }

But after doing that, I get compile errors like this : could not find `ShaderModuleSource` in `wgpu`

[agorgl]

Yep, you need some modifications for this to work, see my opengl-testing branch

[windelbouwman]

Okay, thanks for the headsup! I'm able to build, but trying a few examples, I quickly saw that there is work to do. :)

[kvark]

OpenGL gfx backend does not support

More precisely, all the interaction with the instance, surface, adapter, device, and the queue has to happen on the same thread. But command buffers can be created and recorded on multiple threads, still. So Bevy can get the multithreading benefits. What you aren't going to be able to do (but want to do) is asynchronous resource creation with GL.

Even running with single_threaded_pool bevy has some asset loading/binding issues and a black window is displayed for example in the sprite sample

Since our basic examples run, I wonder why you are getting the black window. Would be good to see what the difference is, and whether our cube example runs on that machine.