Immediate Mode Line/Gizmo Drawing

[tim-blackbird]

Objective

Add a convenient immediate mode drawing API for visual debugging.

Fixes #5619
Alternative to #1625
Partial alternative to #5734

Based off https://github.com/Toqozz/bevy_debug_lines with some changes:

• Simultaneous support for 2D and 3D.
• Methods for basic shapes; circles, spheres, rectangles, boxes, etc.
• 2D methods.
• Removed durations. Seemed niche, and can be handled by users.

Performance

Stress tested using Bevy's recommended optimization settings for the dev profile with the
following command.

cargo run --example many_debug_lines \
    --config "profile.dev.package.\"*\".opt-level=3" \
    --config "profile.dev.opt-level=1"

I dipped to 65-70 FPS at 300,000 lines
CPU: 3700x
RAM Speed: 3200 Mhz
GPU: 2070 super - probably not very relevant, mostly cpu/memory bound

Fancy bloom screenshot

Changelog

• Added GizmoPlugin
• Added Gizmos system parameter for drawing lines and wireshapes.

TODO

• Update changelog
• Update performance numbers
• Add credit to PR description

Future work

• Cache rendering primitives instead of constructing them out of line segments each frame.
• Support for drawing solid meshes
• Interactions. (See bevy_mod_gizmos)
• Fancier line drawing. (See bevy_polyline)
• Support for RenderLayers
• Display gizmos for a certain duration. Currently everything displays for one frame (ie. immediate mode)
• Changing settings per drawn item like drawing on top or drawing to different RenderLayers

Co-Authored By: @lassade felipe.jorge.pereira@gmail.com
Co-Authored By: @The5-1 agaku@hotmail.de
Co-Authored By: @Toqozz toqoz@hotmail.com
Co-Authored By: @nicopap nico@nicopap.ch

[james7132]

Bikeshedding for a better long term name: bevy_gizmos? It'd fit better into the context of a user-facing editor.

[james7132]

Credit should be given to @lassade, @The5-1, and @Toqozz for their prior work in this space.

Could you add Co-Authored By: <EMAIL> to the PR description? Bors will merge it in with that in the final commit to main.

Separately, @lassade's existing implementation for bevy_gizmos seems to also have support for filling in the internal space with a flat color. We can add it in a follow-up PR or leave it be.

[The5-1]

Oh I totally missed this here, good stuff 👌

Was still struggling to get my old attempt ported to 0.8 and then 0.9 hit ;p
Gotta take a closer look at this tomorrow to see how its done!

[nicopap]

Note that I also heavily contributed to Toqozz/bevy_debug_lines. I did the port to the new renderer for 0.6, it was basically an entire rewrite.

[alice-i-cecile]

Once #5303 by @IceSentry is merged, should we reuse the wireframe material here?

[tim-blackbird]

Once #5303 by @IceSentry is merged, should we reuse the wireframe material here?

This PR needs colors to be per vertex with an option to disable depth testing + a 2d version, so that's not an option, and the Material(2d) traits and AsBindGroup are currently not flexible enough to support this.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[github-actions]

You added a new feature but didn't add a description for it. Please update the root Cargo.toml file.

[cart]

Fantastic work!

Ultimately I think we'll want to explore rendering using methods similar to Freya Holmers Shapes lib, as normal "mesh line drawing" has limitations when it comes to thickness, anti-aliasing + quality, etc. Definitely a "hard problem" though. I'm glad we started with the mesh-line approach so we can start building tools + visual debuggers now.

[cart]

Not something to fix here, but the fact that we need to manually plug these values in, despite not using them in the shader, is unfortunate.

[cart]

Turns out this was based on @Toqozz's bevy_debug_lines crate, which is licensed under the mit license only. This will need to be re-licensed if we're going to use it in Bevy.

@Toqozz: can you write "I agree to re-license the code from bevy_debug_lines used in this PR to the dual MIT/Apache-2.0 license Bevy uses" here if you agree to the re-license? No pressure btw. It is your code and you can do whatever you want with it. We will revert if we don't hear from you / if the answer is no.

[Toqozz]

I agree to re-license the code from bevy_debug_lines used in this PR to the dual MIT/Apache-2.0 license Bevy uses.

I didn't even realise that the license was limiting.

[cart]

Much appreciated! Thank you for building cool stuff!