Add RenderTarget::TextureView

[mrchantey]

Objective

We can currently set camera.target to either an Image or Window. For OpenXR & WebXR we need to be able to render to a TextureView.

This partially addresses #115 as with the addition we can create internal and external xr crates.

Solution

A TextureView item is added to the RenderTarget enum. It holds an id which is looked up by a ManualTextureViews resource, much like how Assets<Image> works. I believe this approach was first used by @kcking in their xr fork. The only change is that a u32 is used to index the textures as FromReflect does not support uuid and I don't know how to implement that.

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Changelog

Added

Render: Added RenderTarget::TextureView as a camera.target option, enabling rendering directly to a TextureView.

Migration Guide

References to the RenderTarget enum will need to handle the additional field, ie in match statements.

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Comments

• The wgpu work done by @expenses allows us to create framebuffer texture views from wgpu v0.15, bevy 0.10.
• I got the WebXR techniques from the xr fork by @dekuraan.
• I have tested this with a wip external webxr crate on an Oculus Quest 2.

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[github-actions[bot]]

It looks like your PR is a breaking change, but you didn't provide a migration guide.

Could you add some context on what users should update when this change get released in a new version of Bevy? It will be used to help writing the migration guide for the version. Putting it after a ## Migration Guide will help it get automatically picked up by our tooling.

[MalekiRe]

Bumping

[IceSentry]

So, the implementation seems good to me, but I'm not sure I understand why this is necessary. Isn't the Image render target just a wrapper around targetting a TextureView? As in, couldn't you just use the render to image feature and use the texture view of the image?

[kcking]

So, the implementation seems good to me, but I'm not sure I understand why this is necessary. Isn't the Image render target just a wrapper around targetting a TextureView? As in, couldn't you just use the render to image feature and use the texture view of the image?

There's a quick discord conversation about this, essentially OpenXR requires you to use its TextureViews, you can't provide your own. AFAIU bevy's render to image feature creates new TextureViews so it's incompatible with OpenXR

[IceSentry]

Alright, makes sense. In that case this PR seems fine.

[alice-i-cecile]

Straightforward enough, and on the critical path. Let's see what the community can do with this <3