TrackedRenderPass driven RenderPhases

[kurtkuehnert]

Objective

The current code for creating render passes and executing render phases is quite boilerplate-heavy and repetitive.

I have experimented with further improving the API, based on the proposal by @cart (posted in #7043 (comment)):

// This would create and set up a TrackedRenderPass, which would set the viewport, if it is
// configured on the camera. "pass" would need to be a wrapper over TrackedRenderPass.
let pass = camera.begin_render_pass(render_context, view_entity);
pass.render_phase(opaque_phase, world);

Solution

This PR comprises two changes:

1. The RenderPhases are now executed directly using the TrackedRenderPass, with the API described above.

• Therefore, each TrackedRenderPass is associated with a view_entity.
• Additionally, this alleviates the need to pass around the view_entitys in the render method of Draw functions. Instead, they can be accessed directly from the TrackedRenderPass if they are needed.

old
opaque_phase.render(&mut pass, world, view_entity);

new
pass.render_phase(opaque_phase, world);

2. I have added a TrackedRenderPass::create_for_camera method, that sets up the render pass based on the camera view and depth target.

• This is an attempt to create a method similar to the one proposed by @cart.

let pass = camera.begin_render_pass(render_context, view_entity);
vs
let pass = TrackedRenderPass::create_for_camera(
    render_context,
    "main_alpha_mask_pass_3d",
    view_entity,
    target,
    Operations {
        load: LoadOp::Load,
        store: true,
    },
    Some(depth),
    Some(Operations {
        load: LoadOp::Load,
        store: true,
    }),
    &camera.viewport,
);

• This method replaces the setup for the 2d and 3d pass but is not general enough to accommodate the shadow and the UI pass as well.

I think that 1. is a good idea because from what I have gathered a TrackedRenderPass is always associated with a view_entity anyway.

IMO, 2. is less ideal and I am interested if you have got a better idea. There are just too many different components at play that might or might not be required. I still believe that setting up the render attachments in a way that is simpler and more clear is a worthwhile goal though.

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Changelog

Todo

Migration Guide

Todo

[kurtkuehnert]

Please take a look at #7227 instead.