Custom renderer support?

[Josh015]

Is it possible to build a custom renderer using Bevy's APIs? Specifically, I'd like to make a simple deferred renderer which will require MRT and multiple pass support. Is that even possible currently?

I'm still new to Bevy, so forgive me if I've misunderstood.

EDIT: To clarify, I mean while working within bevy_render rather than completely replacing it and doing a fully custom rendering API.

[bjorn3]

Can you?

Bevy has a very modular design. Almost all components are regular plugins like you could write yourself. You can choose to omit the bevy_render and bevy_wgpu (a wgpu based backend for bevy_render) plugin and write your own renderer instead if you want. To disable bevy_render, I think you can use app.add_plugins_with(DefaultPlugins, |plugins| plugins.disable::<bevy::render::RenderPlugin>().disable::<bevy::wgpu::WgpuPlugin>()) instead of app.add_plugins(DefaultPlugins). You should then add systems to the respective stages to upload all necessary data to the gpu and draw it. Do know that other plugins only have integration for bevy_render, so you will need to add this integration to your own render plugin.

Should you?

Probably not. bevy_render supports pretty much arbitrary render graphs. This includes rendering to a texture and then passing this texture to the next pass. I think it is possible to do what you want within the framework of bevy_render.

[Josh015]

I probably should have been more specific. I meant using a custom render graph, not replacing bevy_render entirely. With that in mind, are there any Bevy examples of rendering to a texture(s) and then rendering that to the screen?

[bjorn3]

With that in mind, are there any Bevy examples of rendering to a texture(s) and then rendering that to the screen?

I don't think so. bevy_render could use some documentation. As far as I know bevy_render is also one of the most lacking areas of Bevy currently.

[FrankenApps]

I have seen this. The code is here

[John-Nagle]

Can you pull out the Bevy renderer and run it without the rest of Bevy? Has anyone done that? Is there a sample 3D program? I've been using Rend3, and I need a plan B in case that project is abandoned.

[JMS55]

Not easily https://github.com/bevyengine/bevy/blob/main/crates/bevy_pbr/Cargo.toml#L16-L26. You could do something where you have a different thread copy values into Bevy's ECS every frame, but yeah not a great idea really.

[John-Nagle]

Yes, Bevy is built as an integrated system, not a game engine that uses a render library.

Thanks anyway.