Currently, we look up each `MeshInputUniform` index in a hash table that
maps the main entity ID to the index every frame. This is inefficient,
cache unfriendly, and unnecessary, as the `MeshInputUniform` index for
an entity remains the same from frame to frame (even if the input
uniform changes). This commit changes the `IndexSet` in the `RenderBin`
to an `IndexMap` that maps the `MainEntity` to `MeshInputUniformIndex`
(a new type that this patch adds for more type safety).
On Caldera with parallel `batch_and_prepare_binned_render_phase`, this
patch improves that function from 3.18 ms to 2.42 ms, a 31% speedup.
# Objective
Because of mesh preprocessing, users cannot rely on
`@builtin(instance_index)` in order to reference external data, as the
instance index is not stable, either from frame to frame or relative to
the total spawn order of mesh instances.
## Solution
Add a user supplied mesh index that can be used for referencing external
data when drawing instanced meshes.
Closes#13373
## Testing
Benchmarked `many_cubes` showing no difference in total frame time.
## Showcase
https://github.com/user-attachments/assets/80620147-aafc-4d9d-a8ee-e2149f7c8f3b
---------
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
# Objective
- It's currently very hard for beginners and advanced users to get a
full understanding of a complete render phase.
## Solution
- Implement a full custom render phase
- The render phase in the example is intended to show a custom stencil
phase that renders the stencil in red directly on the screen
---
## Showcase
<img width="1277" alt="image"
src="https://github.com/user-attachments/assets/e9dc0105-4fb6-463f-ad53-0529b575fd28"
/>
## Notes
More docs to explain what is going on is still needed but the example
works and can already help some people.
We might want to consider using a batched phase and cold specialization
in the future, but the example is already complex enough as it is.
---------
Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>
