bevy/assets
Robert Swain c1a5428f8e
Work around naga/wgpu WGSL instance_index -> GLSL gl_InstanceID bug on WebGL2 (#9383)
naga and wgpu should polyfill WGSL instance_index functionality where it
is not available in GLSL. Until that is done, we can work around it in
bevy using a push constant which is converted to a uniform by naga and
wgpu.

# Objective

- Fixes #9375 

## Solution

- Use a push constant to pass in the base instance to the shader on
WebGL2 so that base instance + gl_InstanceID is used to correctly
represent the instance index.

## TODO

- [ ] Benchmark vs per-object dynamic offset MeshUniform as this will
now push a uniform value per-draw as well as update the dynamic offset
per-batch.
- [x] Test on DX12 AMD/NVIDIA to check that this PR does not regress any
problems that were observed there. (@Elabajaba @robtfm were testing that
last time - help appreciated. <3 )

---

## Changelog

- Added: `bevy_render::instance_index` shader import which includes a
workaround for the lack of a WGSL `instance_index` polyfill for WebGL2
in naga and wgpu for the time being. It uses a push_constant which gets
converted to a plain uniform by naga and wgpu.

## Migration Guide

Shader code before:

```
struct Vertex {
    @builtin(instance_index) instance_index: u32,
...
}

@vertex
fn vertex(vertex_no_morph: Vertex) -> VertexOutput {
...

    var model = mesh[vertex_no_morph.instance_index].model;
```

After:

```
#import bevy_render::instance_index

struct Vertex {
    @builtin(instance_index) instance_index: u32,
...
}

@vertex
fn vertex(vertex_no_morph: Vertex) -> VertexOutput {
...

    var model = mesh[bevy_render::instance_index::get_instance_index(vertex_no_morph.instance_index)].model;
```
2023-08-09 18:38:45 +00:00
..
android-res/mipmap-mdpi android example polish (#845) 2020-11-11 16:31:16 -08:00
branding Minor Dark/Light Logo Tweak (#4051) 2022-02-27 02:09:42 +00:00
data Asset system rework and GLTF scene loading (#693) 2020-10-18 13:48:15 -07:00
docs Improve Mesh documentation (#9061) 2023-07-31 18:55:42 +00:00
environment_maps EnvironmentMapLight, BRDF Improvements (#7051) 2023-02-09 16:46:32 +00:00
fonts Add the license for the FiraMono font (#3589) 2022-05-06 19:29:43 +00:00
models Add morph targets (#8158) 2023-06-22 20:00:01 +00:00
pixel Add pixelated Bevy to assets and an example (#6408) 2022-11-14 22:15:46 +00:00
scenes (De) serialize resources in scenes (#6846) 2023-03-20 21:17:02 +00:00
shaders Work around naga/wgpu WGSL instance_index -> GLSL gl_InstanceID bug on WebGL2 (#9383) 2023-08-09 18:38:45 +00:00
sounds Add simple collision sound to breakout (#4331) 2022-04-14 20:20:38 +00:00
textures Add parallax mapping to bevy PBR (#5928) 2023-04-15 10:25:14 +00:00