Adopted #8266, so copy-pasting the description from there:
# Objective
Support the KHR_texture_transform extension for the glTF loader.
- Fixes#6335
- Fixes#11869
- Implements part of #11350
- Implements the GLTF part of #399
## Solution
As is, this only supports a single transform. Looking at Godot's source,
they support one transform with an optional second one for detail, AO,
and emission. glTF specifies one per texture. The public domain
materials I looked at seem to share the same transform. So maybe having
just one is acceptable for now. I tried to include a warning if multiple
different transforms exist for the same material.
Note the gltf crate doesn't expose the texture transform for the normal
and occlusion textures, which it should, so I just ignored those for
now. (note by @janhohenheim: this is still the case)
Via `cargo run --release --example scene_viewer
~/src/clone/glTF-Sample-Models/2.0/TextureTransformTest/glTF/TextureTransformTest.gltf`:
## Changelog
Support for the
[KHR_texture_transform](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_texture_transform)
extension added. Texture UVs that were scaled, rotated, or offset in a
GLTF are now properly handled.
---------
Co-authored-by: Al McElrath <hello@yrns.org>
Co-authored-by: Kanabenki <lucien.menassol@gmail.com>
# Objective
- Supercedes #8872
- Improve sprite rendering performance after the regression in #9236
## Solution
- Use an instance-rate vertex buffer to store per-instance data.
- Store color, UV offset and scale, and a transform per instance.
- Convert Sprite rect, custom_size, anchor, and flip_x/_y to an affine
3x4 matrix and store the transpose of that in the per-instance data.
This is similar to how MeshUniform uses transpose affine matrices.
- Use a special index buffer that has batches of 6 indices referencing 4
vertices. The lower 2 bits indicate the x and y of a quad such that the
corners are:
```
10 11
00 01
```
UVs are implicit but get modified by UV offset and scale The remaining
upper bits contain the instance index.
## Benchmarks
I will compare versus `main` before #9236 because the results should be
as good as or faster than that. Running `bevymark -- 10000 16` on an M1
Max with `main` at `e8b38925` in yellow, this PR in red:
Looking at the median frame times, that's a 37% reduction from before.
---
## Changelog
- Changed: Improved sprite rendering performance by leveraging an
instance-rate vertex buffer.
---------
Co-authored-by: Giacomo Stevanato <giaco.stevanato@gmail.com>
