Wireframe rendering & Debug lines

[Neo-Zhixing]

While developing games, it would be tremendously helpful to have mesh wireframes & debug lines.

We should be able to enable wireframe rendering easily. In the mean time, there could be a separate DebugLinesComponent similar to Amethyst's implementation for drawing debug lines manually.

We should be able to mark the type of the debug line so that it is possible to enable or disable the rendering of a specific type of debug line globally.

[verzuz]

add polygon_mode: PolyonMode to RasterizationStateDescriptor to allow drawing wireframes 336d070b260591e546ad9372f6423e0be6afbe97
Commit date: 1 week ago (09.09.2020 21:34:37)
was added to wgpu https://github.com/gfx-rs/wgpu - we might use that?

[Neo-Zhixing]

@verzuz This is great news! Yeah wgpu didn't allow us to set the ploygon mode, and it was a major blocker. Now that this was added we can start to look into wireframes and debug lines!

[Neo-Zhixing]

blocked by #542

[alice-i-cecile]

Nice functionality for debug lines currently exists in bevy_mod_raycast. This is a helpful stopgap, and worth looking at for when we want to include this functionality natively.

[lassade]

Hey a bit of shameless self promotion I'm working on a crate to implement debug gizmos (bevy_gizmos)[https://github.com/lassade/bevy_gizmos] I got many features working as well as debug lines, thers also other crate liked in,

bevy_mod_raycast have debug lines?

[Neo-Zhixing]

With #562 merged we can close this issue now. For debug lines they could be implemented in external packages. We can open a separate issue if we want debug lines in the core package as well.