Disable bindless on a per-material basis if the specific material uses more samplers than are available on the device. (bevyengine#17155)

Some hardware and driver combos, such as Intel Iris Xe, have low limits
on the numbers of samplers per shader, causing an overflow. With
first-class bindless arrays, `wgpu` should be able to work around this
limitation eventually, but for now we need to disable bindless materials
on those platforms.

This is an alternative to PR bevyengine#17107 that calculates the precise number
of samplers needed and compares to the hardware sampler limit,
transparently falling back to non-bindless if the limit is exceeded.

Fixes bevyengine#16988.

Author: pcwalton

crates/bevy_pbr/src/material_bind_groups.rs

@@ -19,7 +19,6 @@ use bevy_render::{
         UnpreparedBindGroup, WgpuSampler, WgpuTextureView,
     },
     renderer::RenderDevice,
-    settings::WgpuFeatures,
     texture::FallbackImage,
 };
 use bevy_utils::{default, tracing::error, HashMap};
@@ -795,10 +794,7 @@ pub fn material_uses_bindless_resources<M>(render_device: &RenderDevice) -> bool
 where
     M: Material,
 {
-    M::bindless_slot_count().is_some()
-        && render_device
-            .features()
-            .contains(WgpuFeatures::BUFFER_BINDING_ARRAY | WgpuFeatures::TEXTURE_BINDING_ARRAY)
+    M::bindless_slot_count().is_some() && M::bindless_supported(render_device)
 }
 
 impl FromWorld for FallbackBindlessResources {

crates/bevy_render/macros/src/as_bind_group.rs

@@ -132,6 +132,11 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
         }
     };
 
+    // Count the number of sampler fields needed. We might have to disable
+    // bindless if bindless arrays take the GPU over the maximum number of
+    // samplers.
+    let mut sampler_binding_count = 0;
+
     // Read field-level attributes
     for field in fields {
         // Search ahead for texture attributes so we can use them with any
@@ -341,6 +346,8 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
                         )
                     });
 
+                    sampler_binding_count += 1;
+
                     binding_layouts.push(quote! {
                         #render_path::render_resource::BindGroupLayoutEntry {
                             binding: #binding_index,
@@ -417,6 +424,8 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
                         )
                     });
 
+                    sampler_binding_count += 1;
+
                     binding_layouts.push(quote!{
                         #render_path::render_resource::BindGroupLayoutEntry {
                             binding: #binding_index,
@@ -440,11 +449,7 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
         Some(_) => {
             quote! {
                 let (#uniform_binding_type, #uniform_buffer_usages) =
-                    if render_device.features().contains(
-                        #render_path::settings::WgpuFeatures::BUFFER_BINDING_ARRAY |
-                        #render_path::settings::WgpuFeatures::TEXTURE_BINDING_ARRAY
-                    ) && render_device.limits().max_storage_buffers_per_shader_stage > 0 &&
-                    !force_no_bindless {
+                    if Self::bindless_supported(render_device) && !force_no_bindless {
                         (
                             #render_path::render_resource::BufferBindingType::Storage { read_only: true },
                             #render_path::render_resource::BufferUsages::STORAGE,
@@ -563,6 +568,17 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
         (prepared_data.clone(), prepared_data)
     };
 
+    // Calculate the number of samplers that we need, so that we don't go over
+    // the limit on certain platforms. See
+    // https://github.com/bevyengine/bevy/issues/16988.
+    let samplers_needed = match attr_bindless_count {
+        Some(Lit::Int(ref bindless_count)) => match bindless_count.base10_parse::<u32>() {
+            Ok(bindless_count) => sampler_binding_count * bindless_count,
+            Err(_) => 0,
+        },
+        _ => 0,
+    };
+
     // Calculate the actual number of bindless slots, taking hardware
     // limitations into account.
     let (bindless_slot_count, actual_bindless_slot_count_declaration) = match attr_bindless_count {
@@ -571,13 +587,19 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
                 fn bindless_slot_count() -> Option<u32> {
                     Some(#bindless_count)
                 }
+
+                fn bindless_supported(render_device: &#render_path::renderer::RenderDevice) -> bool {
+                    render_device.features().contains(
+                        #render_path::settings::WgpuFeatures::BUFFER_BINDING_ARRAY |
+                        #render_path::settings::WgpuFeatures::TEXTURE_BINDING_ARRAY
+                    ) &&
+                    render_device.limits().max_storage_buffers_per_shader_stage > 0 &&
+                        render_device.limits().max_samplers_per_shader_stage >= #samplers_needed
+                }
             },
             quote! {
-                let #actual_bindless_slot_count = if render_device.features().contains(
-                    #render_path::settings::WgpuFeatures::BUFFER_BINDING_ARRAY |
-                    #render_path::settings::WgpuFeatures::TEXTURE_BINDING_ARRAY
-                ) && render_device.limits().max_storage_buffers_per_shader_stage > 0 &&
-                !force_no_bindless {
+                let #actual_bindless_slot_count = if Self::bindless_supported(render_device) &&
+                        !force_no_bindless {
                     ::core::num::NonZeroU32::new(#bindless_count)
                 } else {
                     None

crates/bevy_render/src/render_resource/bind_group.rs

@@ -342,6 +342,15 @@ pub trait AsBindGroup {
         None
     }
 
+    /// True if the hardware *actually* supports bindless textures for this
+    /// type, taking the device and driver capabilities into account.
+    ///
+    /// If this type doesn't use bindless textures, then the return value from
+    /// this function is meaningless.
+    fn bindless_supported(_: &RenderDevice) -> bool {
+        true
+    }
+
     /// label
     fn label() -> Option<&'static str> {
         None