Bevy 0.12 panics when loading a skinned GLTF mesh with shadow-enabled directional light in WASM

[idanarye]

Bevy version

Bevy v0.12.0

[Optional] Relevant system information

• the Rust version you're using (you can get this by running cargo --version)
  I get this both when building locally and

  $ cargo --version
  
  cargo 1.73.0 (9c4383fb5 2023-08-26)

• the operating system or browser used, including its version

  $ uname -srvmpio
  
  Linux 6.5.9-arch2-1 #1 SMP PREEMPT_DYNAMIC Thu, 26 Oct 2023 00:52:20 +0000 x86_64 unknown unknown GNU/Linux

  This is a WASM bug though, so the browser version is probably more important:

  $ firefox --full-version
  
  Mozilla Firefox 119.0 20231023160744 20231023160744 

If your bug is rendering-related, copy the adapter info that appears when you run Bevy.

Formatted for readability:

INFO /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bevy_render-0.12.0/src/renderer/mod.rs:140 AdapterInfo {
    name: "NVIDIA GeForce GTX 980/PCIe/SSE2",
    vendor: 4318,
    device: 0,
    device_type: Other,
    driver: "",
    driver_info: "",
    backend: Gl
}

What you did

1. Created a simple skinned mesh in Blender - I just added an armature to the startup cube (without automatic weights). Didn't even animate it.
2. Exported to GLTF (bug replicates with either GLTF or GLB)
3. Loaded the GLTF it in Bevy.
4. Added a directional light with shadows.
5. Built it for WASM, with the WebGL2 backend.
6. Tried to run it in the browser.

Note that this is a minimal example. If I don't add an armature - the bug does not replicate. If I don't enable shadows on the directional lights - the bug does not replicate. I have no idea how these two are related...

Here is a repository that demonstrates the problem: https://github.com/idanarye/demonstrate-bevy-0.12-wasm-shadows-bug

What went wrong

• what were you expecting? - The model to show without panicing, as it does with Bevy 0.11
• what actually happened? - on Bevy 0.12, it does not show the model, and panics with the following error and stack trace:

  panicked at 'No uniform for push constant', /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wgpu-hal-0.17.2/src/gles/command.rs:725:17
  
  Stack:
  
  __wbg_get_imports/imports.wbg.__wbg_new_abda76e883ba8a5f@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template.js:401:21
  console_error_panic_hook::hook::h810134e5e71475d7@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[12678]:0x1072fd2
  core::ops::function::Fn::call::hd416b0b98723df16@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[61618]:0x162d96b
  std::panicking::rust_panic_with_hook::h5cee2a9564faeb6d@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[22527]:0x13b7029
  std::panicking::begin_panic_handler::{{closure}}::h38a949ca54e64e6b@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[26190]:0x146183c
  std::sys_common::backtrace::__rust_end_short_backtrace::hc4f3d2fd3090193f@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[60893]:0x162c01a
  rust_begin_unwind@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[34172]:0x155d6d5
  core::panicking::panic_fmt::h8a19fa1eb63fbb67@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[37376]:0x159a8a4
  wgpu_hal::gles::command::<impl wgpu_hal::CommandEncoder<wgpu_hal::gles::Api> for wgpu_hal::gles::CommandEncoder>::set_push_constants::haa0ecf7056cb7ae8@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[13562]:0x10dc2c0
  wgpu_core::command::render::<impl wgpu_core::global::Global<G>>::command_encoder_run_render_pass_impl::h9147f31103eb7ab8@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[431]:0xcd969
  <wgpu::backend::direct::Context as wgpu::context::Context>::command_encoder_end_render_pass::h55fd06be94875af7@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[2700]:0x801c7c
  <T as wgpu::context::DynContext>::command_encoder_end_render_pass::had3876df2f7853d3@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[36008]:0x1582dbe
  <wgpu::RenderPass as core::ops::drop::Drop>::drop::h14e549d452e2b093@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[28777]:0x14c3d9b
  <bevy_pbr::render::light::ShadowPassNode as bevy_render::render_graph::node::Node>::run::hcc2fd584a282e0c6@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[7648]:0xd68514
  bevy_render::renderer::graph_runner::RenderGraphRunner::run_graph::h9ec389af8302ff13@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[547]:0x23f95c
  bevy_render::renderer::graph_runner::RenderGraphRunner::run_graph::h9ec389af8302ff13@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[547]:0x23fad1
  bevy_render::renderer::graph_runner::RenderGraphRunner::run::h2c80c4203cc4cb19@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[6118]:0xc2086b
  bevy_render::renderer::render_system::h5c5451905bb4512a@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[884]:0x3ead92
  <bevy_ecs::system::exclusive_function_system::ExclusiveFunctionSystem<Marker,F> as bevy_ecs::system::system::System>::run::h9eb783eb279173d7@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[36238]:0x158744a
  <bevy_ecs::schedule::executor::single_threaded::SingleThreadedExecutor as bevy_ecs::schedule::executor::SystemExecutor>::run::h603e5a5c4d0b1965@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[1598]:0x5ed68d
  bevy_ecs::schedule::schedule::Schedule::run::hfe5020fa9d98a947@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[20325]:0x1336368
  bevy_ecs::world::World::schedule_scope::had99d41c0e09f8c0@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[6187]:0xc30f51
  bevy_app::app::App::update::h77e2765c8f6c80f3@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[20747]:0x135195e
  winit::platform_impl::platform::event_loop::EventLoop<T>::spawn::{{closure}}::h56d5bff1e1a4edac@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[470]:0x178b5f
  winit::platform_impl::platform::event_loop::runner::Shared<T>::handle_event::h56dd87b15f500875@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[4311]:0xa42367
  winit::platform_impl::platform::event_loop::runner::Shared<T>::run_until_cleared::hed4a735001e2e75e@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[6526]:0xc7c948
  winit::platform_impl::platform::backend::timeout::AnimationFrameRequest::new::{{closure}}::h52e469b6a796274b@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[36916]:0x1593190
  <dyn core::ops::function::FnMut<()>+Output = R as wasm_bindgen::closure::WasmClosure>::describe::invoke::h126391ccdb7bc256@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:wasm-function[41621]:0x15ccaa1
  __wbg_adapter_51@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template.js:222:10
  real@https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template.js:203:20
  
  
  bevy_github_ci_template.js:417:21
      __wbg_error_f851667af71bcfc6 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template.js:417
      h810134e5e71475d7 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:17248425
      hd416b0b98723df16 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:23255403
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      h38a949ca54e64e6b https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:21370940
      hc4f3d2fd3090193f https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:23248922
      rust_begin_unwind https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:22402773
      h8a19fa1eb63fbb67 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:22653092
      wgpu_hal::gles::command::<impl wgpu_hal::CommandEncoder<wgpu_hal::gles::Api> for wgpu_hal::gles::CommandEncoder>::set_push_constants::haa0ecf7056cb7ae8 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:17679040
      wgpu_core::command::render::<impl wgpu_core::global::Global<G>>::command_encoder_run_render_pass_impl::h9147f31103eb7ab8 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:842089
      <wgpu::backend::direct::Context as wgpu::context::Context>::command_encoder_end_render_pass::h55fd06be94875af7 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:8395900
      <T as wgpu::context::DynContext>::command_encoder_end_render_pass::had3876df2f7853d3 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:22556094
      <wgpu::RenderPass as core::ops::drop::Drop>::drop::h14e549d452e2b093 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:21773723
      <bevy_pbr::render::light::ShadowPassNode as bevy_render::render_graph::node::Node>::run::hcc2fd584a282e0c6 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:14058772
      h9ec389af8302ff13 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:2357596
      h9ec389af8302ff13 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:2357969
      h2c80c4203cc4cb19 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:12716139
      h5c5451905bb4512a https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:4107666
      <bevy_ecs::system::exclusive_function_system::ExclusiveFunctionSystem<Marker,F> as bevy_ecs::system::system::System>::run::h9eb783eb279173d7 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:22574154
      <bevy_ecs::schedule::executor::single_threaded::SingleThreadedExecutor as bevy_ecs::schedule::executor::SystemExecutor>::run::h603e5a5c4d0b1965 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:6215309
      hfe5020fa9d98a947 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:20145000
      had99d41c0e09f8c0 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:12783441
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      h56d5bff1e1a4edac https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:1543007
      h56dd87b15f500875 https://idanarye.github.io/demonstrate-bevy-0.12-wasm-shadows-bug/bevy-0.12/bevy_github_ci_template_bg.wasm:10756967
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[superdump]

I think on webgl2 we had to add a workaround for the base instance index not being part of the instance index value and we had to get the base instance index into the shader via a push constant. I think the bug is something to do with that but can’t look into it right now. See instance_index.wgsl and its get_instance_index function.

[cart]

Just repro-ed with the animated_fox example.

[DGriffin91]

It looks like animated_fox works on bevy main. Was there a PR that fixed this?

Also discussion about possible workaround on discord: https://discord.com/channels/691052431525675048/743663924229963868/1174881166705315880

[cart]

Following up: sounds like this is only broken on some platform configurations. Still broken, but so far only reproducible on linux + nvidia.

[ramirezmike]

Following up: sounds like this is only broken on some platform configurations. Still broken, but so far only reproducible on linux + nvidia.

and linux + integrated radeon graphics 👍

[cart]

A summary of the problem:

1. As of Bevy 0.12, we're using a new approach to accessing mesh information that relies on @builtin(instance_index). Sadly, current versions of wgpu do not support instance_index on WebGL2 (main does support this but there has not been a release yet), so we worked around this with push constants (which are emulated as uniforms via wgpu because WebGL2 doesn't natively support push constants).
2. Sadly, we've discovered that wgpu also has issues with push constants on WebGL 2. Again, this has been fixed on main, but does not have a release yet

@cwfitzgerald let us know that one way to work around this is to ensure that every shader uses the push constant. Sure enough, by adding this to prepass.wgsl, we do fix the problem:

#ifdef VERTEX_OUTPUT_INSTANCE_INDEX
    out.instance_index = get_instance_index(vertex_no_morph.instance_index);
#endif
    // Hack: adding this line ensures the push constant is always used, as get_instance_index accesses the push constant
    out.position.x += f32(get_instance_index(0u)) * 0.00001;
    return out;
}

However, this breaks down the second a shader is used that doesn't use the push constant. Therefore it is not a "real" fix, although it does make simple examples work / any game that sticks with the built in materials + shaders.

Therefore as a short term solution I think we should roll with this.

One medium term-solution is to cut out the "push constant" entirely and use a uniform buffer. Given that this is what wgpu's WebGL2 push constant emulation is doing anyway, thats actually not too big of a deal. This will take a bit of engineering work to update our data flow.

The long-term solution is to wait for the next wgpu release so we can use instance_index everywhere.

[cwfitzgerald]

Given that this is what wgpu's WebGL2 push constant emulation is doing anyway,

This isn't actually true, we emulate them using gl uniforms which are closer to push constants than a proper buffer. If this change is made, once 0.19 comes out, it probably should be rolled back.

[cart]

Makes sense. Thanks!