FallbackImage only supports TextureDimension::D2

[bonsairobo]

Bevy version

0.9

What you did

I tried to use the AsBindGroup derive for a custom material that uses optional array textures:

#[derive(AsBindGroup, Reflect, FromReflect, Debug, Clone, TypeUuid)]
#[uuid = "2f3d7f74-4bf7-4f32-98cd-858edafa5ca2"]
#[bind_group_data(MyMaterialKey)]
#[uniform(0, MyMaterialUniform)]
#[reflect(Default, Debug)]
pub struct MyMaterial {
    pub base_color: Color,

    #[texture(1, dimension = "2d_array")]
    #[sampler(2)]
    pub base_color_texture: Option<Handle<Image>>,

   ...
}

What went wrong

The application crashed while trying to create the bind group. See full crash output below. The reason was:

wgpu error: Validation Error

Caused by:
    In Device::create_bind_group
    texture binding 1 expects dimension = D2Array, but given a view with dimension = D2

Additional information

Theory of Root Cause

As the title suggests, I believe the root cause is that FallbackImage is only ever created with TextureDimension::D2. So when I provide None for the optional image, the fallback has a mismatch with the expected texture binding layout.

stdout/stderr + backtrace

2022-12-11T23:41:31.770452Z  INFO winit::platform_impl::platform::x11::window: Guessed window scale factor: 1.25    
2022-12-11T23:41:33.156370Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 3070 Laptop GPU", vendor: 4318, device: 9373, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "510.85.02", backend: Vulkan }
2022-12-11T23:41:33.704555Z ERROR wgpu::backend::direct: Handling wgpu errors as fatal by default    
thread 'Compute Task Pool (2)' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_bind_group
    texture binding 1 expects dimension = D2Array, but given a view with dimension = D2

', /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/backend/direct.rs:2403:5
stack backtrace:
   0: rust_begin_unwind
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:142:14
   2: wgpu::backend::direct::default_error_handler
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/backend/direct.rs:2403:5
   3: core::ops::function::Fn::call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:77:5
   4: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1954:9
   5: wgpu::backend::direct::ErrorSinkRaw::handle_error
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/backend/direct.rs:2389:17
   6: wgpu::backend::direct::Context::handle_error
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/backend/direct.rs:254:9
   7: <wgpu::backend::direct::Context as wgpu::Context>::device_create_bind_group
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/backend/direct.rs:1298:13
   8: wgpu::Device::create_bind_group
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.14.2/src/lib.rs:2170:17
   9: bevy_render::renderer::render_device::RenderDevice::create_bind_group
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.9.1/src/renderer/render_device.rs:75:31
  10: <bevy_triplanar_splatting::TriplanarMaterial as bevy_render::render_resource::bind_group::AsBindGroup>::as_bind_group
             at ./src/lib.rs:22:10
  11: bevy_pbr::material::prepare_material
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_pbr-0.9.1/src/material.rs:590:20
  12: bevy_pbr::material::prepare_materials
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_pbr-0.9.1/src/material.rs:566:15
  13: core::ops::function::FnMut::call_mut
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:164:5
  14: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:294:13
  15: <Func as bevy_ecs::system::function_system::SystemParamFunction<(),Out,(F0,F1,F2,F3,F4,F5,F6),()>>::run::call_inner
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/system/function_system.rs:579:21
  16: <Func as bevy_ecs::system::function_system::SystemParamFunction<(),Out,(F0,F1,F2,F3,F4,F5,F6),()>>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/system/function_system.rs:582:17
  17: <bevy_ecs::system::function_system::FunctionSystem<In,Out,Param,Marker,F> as bevy_ecs::system::system::System>::run_unsafe
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/system/function_system.rs:409:19
  18: bevy_ecs::schedule::executor_parallel::ParallelExecutor::prepare_systems::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/schedule/executor_parallel.rs:218:26
  19: bevy_ecs::schedule::executor_parallel::ParallelExecutor::prepare_systems::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/schedule/executor_parallel.rs:258:21
  20: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/mod.rs:91:19
  21: async_executor::Executor::spawn::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/async-executor-1.5.0/src/lib.rs:139:19
  22: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/mod.rs:91:19
  23: async_task::raw::RawTask<F,T,S>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/async-task-4.3.0/src/raw.rs:511:20
  24: async_task::runnable::Runnable::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/async-task-4.3.0/src/runnable.rs:309:18
  25: async_executor::Executor::run::{{closure}}::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/async-executor-1.5.0/src/lib.rs:230:21
  26: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/mod.rs:91:19
  27: <futures_lite::future::Or<F1,F2> as core::future::future::Future>::poll
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:529:33
  28: async_executor::Executor::run::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/async-executor-1.5.0/src/lib.rs:237:31
  29: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/mod.rs:91:19
  30: futures_lite::future::block_on::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:89:27
  31: std::thread::local::LocalKey<T>::try_with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:445:16
  32: std::thread::local::LocalKey<T>::with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:421:9
  33: futures_lite::future::block_on
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:79:5
  34: bevy_tasks::task_pool::TaskPool::new_internal::{{closure}}::{{closure}}::{{closure}}::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:128:37
  35: std::panicking::try::do_call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:492:40
  36: __rust_try
  37: std::panicking::try
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:456:19
  38: std::panic::catch_unwind
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panic.rs:137:14
  39: bevy_tasks::task_pool::TaskPool::new_internal::{{closure}}::{{closure}}::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:122:43
  40: std::thread::local::LocalKey<T>::try_with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:445:16
  41: std::thread::local::LocalKey<T>::with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:421:9
  42: bevy_tasks::task_pool::TaskPool::new_internal::{{closure}}::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:120:25
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:273:45
stack backtrace:
   0: rust_begin_unwind
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:142:14
   2: core::panicking::panic
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:48:5
   3: core::option::Option<T>::unwrap
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/option.rs:775:21
   4: bevy_tasks::task_pool::TaskPool::scope::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:273:34
   5: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/mod.rs:91:19
   6: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/future.rs:124:9
   7: <&mut F as core::future::future::Future>::poll
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/future/future.rs:112:9
   8: <futures_lite::future::PollOnce<F> as core::future::future::Future>::poll
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:194:15
   9: futures_lite::future::block_on::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:89:27
  10: std::thread::local::LocalKey<T>::try_with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:445:16
  11: std::thread::local::LocalKey<T>::with
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/thread/local.rs:421:9
  12: futures_lite::future::block_on
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-lite-1.12.0/src/future.rs:79:5
  13: bevy_tasks::task_pool::TaskPool::scope
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_tasks-0.9.1/src/task_pool.rs:283:39
  14: <bevy_ecs::schedule::executor_parallel::ParallelExecutor as bevy_ecs::schedule::executor::ParallelSystemExecutor>::run_systems
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/schedule/executor_parallel.rs:127:9
  15: <bevy_ecs::schedule::stage::SystemStage as bevy_ecs::schedule::stage::Stage>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.9.1/src/schedule/stage.rs:802:17
  16: <bevy_render::RenderPlugin as bevy_app::plugin::Plugin>::build::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.9.1/src/lib.rs:261:21
  17: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1954:9
  18: bevy_app::app::App::update
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.9.1/src/app.rs:154:13
  19: bevy_winit::winit_runner_with::{{closure}}
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.9.1/src/lib.rs:600:21
  20: winit::platform_impl::platform::sticky_exit_callback
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/platform_impl/linux/mod.rs:849:9
  21: winit::platform_impl::platform::x11::EventLoop<T>::run_return::single_iteration
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/platform_impl/linux/x11/mod.rs:363:17
  22: winit::platform_impl::platform::x11::EventLoop<T>::run_return
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/platform_impl/linux/x11/mod.rs:448:31
  23: winit::platform_impl::platform::x11::EventLoop<T>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/platform_impl/linux/x11/mod.rs:503:25
  24: winit::platform_impl::platform::EventLoop<T>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/platform_impl/linux/mod.rs:755:56
  25: winit::event_loop::EventLoop<T>::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/winit-0.27.5/src/event_loop.rs:278:9
  26: bevy_winit::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.9.1/src/lib.rs:263:5
  27: bevy_winit::winit_runner_with
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.9.1/src/lib.rs:645:9
  28: bevy_winit::winit_runner
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.9.1/src/lib.rs:303:5
  29: core::ops::function::Fn::call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:77:5
  30: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1954:9
  31: bevy_app::app::App::run
             at /home/duncan/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.9.1/src/app.rs:168:9
  32: render::main
             at ./examples/render.rs:6:5
  33: core::ops::function::FnOnce::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:248:5

[bonsairobo]

Thankfully it's not too hard to work around this by making the texture mandatory, and then the user can supply their own fallback.

[torsteingrindvik]

I've been having problems with this too, 3D textures for me.

Like you said if not using Option<_> for the image you can work around it.

I found it easiest to use include_bytes! to create an image on the spot and use that, but that's circumventing the asset system and can lead to annoying loading times.

If using the asset system I was tripped up by errors stating I was supplying a 2D image even though I was modifying the texture descriptor and view after the asset was created.
Turns out it's very easy to assign a Handle<Image> to some material and have it crash your app while it's in LoadingStage::Loading.
I then had to make sure my render pipeline setup was not attempting to run any pipeline with such items until it was both loaded and I hade done some fixups on the loaded image.

Summary: +1 to finding a solution to this, as this took me quite some time to debug.

[bonsairobo]

If using the asset system I was tripped up by errors stating I was supplying a 2D image even though I was modifying the texture descriptor and view after the asset was created.

I also tried fixing up my images after they were loaded by the asset server, and none of the system orderings that I tried worked. For me it was necessary to wait until the images had been loaded and modified before trying to spawn anything with those handles.

[torsteingrindvik]

If using the asset system I was tripped up by errors stating I was supplying a 2D image even though I was modifying the texture descriptor and view after the asset was created.

I also tried fixing up my images after they were loaded by the asset server, and none of the system orderings that I tried worked. For me it was necessary to wait until the images had been loaded and modified before trying to spawn anything with those handles.

Yes, in effect that's what I am doing too. I hold off on adding my custom material until it's loaded and modified. Because as soon as I do my_material_assets.add(<instance>) the Material2dPlugin systems will pick it up and try to use the Handle<Image> within my material, and that crashes unless the image has had a "fixup".

[bonsairobo]

From looking at the AsBindGroup derive macro implementation, the fallback image's TextureView is used when the binding's Option<Handle<Image>> is None. Because this relies on already having a view that matches the desired binding dimensions, I think the solution will require creating a separate GpuImage for each possible TextureViewDimension.

Quoting the docs on FallbackImage:

FallbackImage defaults to a 1x1 fully white texture, making blending colors with it a no-op.

Assuming this holds for any TextureViewDimension, it should be OK to create more fallbacks.

This solution would require removing the Deref impl from FallbackImage.

I can take a swing at implementing this solution unless someone quickly yells at me that I should do something else ;)

[bonsairobo]

PR is ready for review!