bevy_render/render_resource/
bind_group.rs

1use crate::renderer::WgpuWrapper;
2use crate::{
3    define_atomic_id,
4    render_asset::RenderAssets,
5    render_resource::{BindGroupLayout, Buffer, Sampler, TextureView},
6    renderer::RenderDevice,
7    texture::GpuImage,
8};
9use bevy_derive::{Deref, DerefMut};
10use bevy_ecs::system::{SystemParam, SystemParamItem};
11pub use bevy_render_macros::AsBindGroup;
12use core::ops::Deref;
13use encase::ShaderType;
14use thiserror::Error;
15use wgpu::{
16    BindGroupEntry, BindGroupLayoutEntry, BindingResource, SamplerBindingType, TextureViewDimension,
17};
18
19use super::{BindlessDescriptor, BindlessSlabResourceLimit};
20
21define_atomic_id!(BindGroupId);
22
23/// Bind groups are responsible for binding render resources (e.g. buffers, textures, samplers)
24/// to a [`TrackedRenderPass`](crate::render_phase::TrackedRenderPass).
25/// This makes them accessible in the pipeline (shaders) as uniforms.
26///
27/// This is a lightweight thread-safe wrapper around wgpu's own [`BindGroup`](wgpu::BindGroup),
28/// which can be cloned as needed to workaround lifetime management issues. It may be converted
29/// from and dereferences to wgpu's [`BindGroup`](wgpu::BindGroup).
30///
31/// Can be created via [`RenderDevice::create_bind_group`](RenderDevice::create_bind_group).
32#[derive(Clone, Debug)]
33pub struct BindGroup {
34    id: BindGroupId,
35    value: WgpuWrapper<wgpu::BindGroup>,
36}
37
38impl BindGroup {
39    /// Returns the [`BindGroupId`] representing the unique ID of the bind group.
40    #[inline]
41    pub fn id(&self) -> BindGroupId {
42        self.id
43    }
44}
45
46impl PartialEq for BindGroup {
47    fn eq(&self, other: &Self) -> bool {
48        self.id == other.id
49    }
50}
51
52impl Eq for BindGroup {}
53
54impl core::hash::Hash for BindGroup {
55    fn hash<H: core::hash::Hasher>(&self, state: &mut H) {
56        self.id.0.hash(state);
57    }
58}
59
60impl From<wgpu::BindGroup> for BindGroup {
61    fn from(value: wgpu::BindGroup) -> Self {
62        BindGroup {
63            id: BindGroupId::new(),
64            value: WgpuWrapper::new(value),
65        }
66    }
67}
68
69impl<'a> From<&'a BindGroup> for Option<&'a wgpu::BindGroup> {
70    fn from(value: &'a BindGroup) -> Self {
71        Some(value.deref())
72    }
73}
74
75impl<'a> From<&'a mut BindGroup> for Option<&'a wgpu::BindGroup> {
76    fn from(value: &'a mut BindGroup) -> Self {
77        Some(&*value)
78    }
79}
80
81impl Deref for BindGroup {
82    type Target = wgpu::BindGroup;
83
84    #[inline]
85    fn deref(&self) -> &Self::Target {
86        &self.value
87    }
88}
89
90/// Converts a value to a [`BindGroup`] with a given [`BindGroupLayout`], which can then be used in Bevy shaders.
91/// This trait can be derived (and generally should be). Read on for details and examples.
92///
93/// This is an opinionated trait that is intended to make it easy to generically
94/// convert a type into a [`BindGroup`]. It provides access to specific render resources,
95/// such as [`RenderAssets<GpuImage>`] and [`crate::texture::FallbackImage`]. If a type has a [`Handle<Image>`](bevy_asset::Handle),
96/// these can be used to retrieve the corresponding [`Texture`](crate::render_resource::Texture) resource.
97///
98/// [`AsBindGroup::as_bind_group`] is intended to be called once, then the result cached somewhere. It is generally
99/// ok to do "expensive" work here, such as creating a [`Buffer`] for a uniform.
100///
101/// If for some reason a [`BindGroup`] cannot be created yet (for example, the [`Texture`](crate::render_resource::Texture)
102/// for an [`Image`](bevy_image::Image) hasn't loaded yet), just return [`AsBindGroupError::RetryNextUpdate`], which signals that the caller
103/// should retry again later.
104///
105/// # Deriving
106///
107/// This trait can be derived. Field attributes like `uniform` and `texture` are used to define which fields should be bindings,
108/// what their binding type is, and what index they should be bound at:
109///
110/// ```
111/// # use bevy_render::render_resource::*;
112/// # use bevy_image::Image;
113/// # use bevy_color::LinearRgba;
114/// # use bevy_asset::Handle;
115/// # use bevy_render::storage::ShaderStorageBuffer;
116///
117/// #[derive(AsBindGroup)]
118/// struct CoolMaterial {
119///     #[uniform(0)]
120///     color: LinearRgba,
121///     #[texture(1)]
122///     #[sampler(2)]
123///     color_texture: Handle<Image>,
124///     #[storage(3, read_only)]
125///     storage_buffer: Handle<ShaderStorageBuffer>,
126///     #[storage(4, read_only, buffer)]
127///     raw_buffer: Buffer,
128///     #[storage_texture(5)]
129///     storage_texture: Handle<Image>,
130/// }
131/// ```
132///
133/// In WGSL shaders, the binding would look like this:
134///
135/// ```wgsl
136/// @group(2) @binding(0) var<uniform> color: vec4<f32>;
137/// @group(2) @binding(1) var color_texture: texture_2d<f32>;
138/// @group(2) @binding(2) var color_sampler: sampler;
139/// @group(2) @binding(3) var<storage> storage_buffer: array<f32>;
140/// @group(2) @binding(4) var<storage> raw_buffer: array<f32>;
141/// @group(2) @binding(5) var storage_texture: texture_storage_2d<rgba8unorm, read_write>;
142/// ```
143/// Note that the "group" index is determined by the usage context. It is not defined in [`AsBindGroup`]. For example, in Bevy material bind groups
144/// are generally bound to group 2.
145///
146/// The following field-level attributes are supported:
147///
148/// ## `uniform(BINDING_INDEX)`
149///
150///  * The field will be converted to a shader-compatible type using the [`ShaderType`] trait, written to a [`Buffer`], and bound as a uniform.
151///    [`ShaderType`] is implemented for most math types already, such as [`f32`], [`Vec4`](bevy_math::Vec4), and
152///    [`LinearRgba`](bevy_color::LinearRgba). It can also be derived for custom structs.
153///
154/// ## `texture(BINDING_INDEX, arguments)`
155///
156///  * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Texture`](crate::render_resource::Texture)
157///    GPU resource, which will be bound as a texture in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
158///    most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
159///    [`None`], the [`crate::texture::FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `sampler` binding attribute
160///    (with a different binding index) if a binding of the sampler for the [`Image`](bevy_image::Image) is also required.
161///
162/// | Arguments             | Values                                                                  | Default              |
163/// |-----------------------|-------------------------------------------------------------------------|----------------------|
164/// | `dimension` = "..."   | `"1d"`, `"2d"`, `"2d_array"`, `"3d"`, `"cube"`, `"cube_array"`          | `"2d"`               |
165/// | `sample_type` = "..." | `"float"`, `"depth"`, `"s_int"` or `"u_int"`                            | `"float"`            |
166/// | `filterable` = ...    | `true`, `false`                                                         | `true`               |
167/// | `multisampled` = ...  | `true`, `false`                                                         | `false`              |
168/// | `visibility(...)`     | `all`, `none`, or a list-combination of `vertex`, `fragment`, `compute` | `vertex`, `fragment` |
169///
170/// ## `storage_texture(BINDING_INDEX, arguments)`
171///
172/// * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Texture`](crate::render_resource::Texture)
173///   GPU resource, which will be bound as a storage texture in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
174///   most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
175///   [`None`], the [`crate::texture::FallbackImage`] resource will be used instead.
176///
177/// | Arguments              | Values                                                                                     | Default       |
178/// |------------------------|--------------------------------------------------------------------------------------------|---------------|
179/// | `dimension` = "..."    | `"1d"`, `"2d"`, `"2d_array"`, `"3d"`, `"cube"`, `"cube_array"`                             | `"2d"`        |
180/// | `image_format` = ...   | any member of [`TextureFormat`](crate::render_resource::TextureFormat)                     | `Rgba8Unorm`  |
181/// | `access` = ...         | any member of [`StorageTextureAccess`](crate::render_resource::StorageTextureAccess)       | `ReadWrite`   |
182/// | `visibility(...)`      | `all`, `none`, or a list-combination of `vertex`, `fragment`, `compute`                    | `compute`     |
183///
184/// ## `sampler(BINDING_INDEX, arguments)`
185///
186/// * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Sampler`] GPU
187///   resource, which will be bound as a sampler in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
188///   most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
189///   [`None`], the [`crate::texture::FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `texture` binding attribute
190///   (with a different binding index) if a binding of the texture for the [`Image`](bevy_image::Image) is also required.
191///
192/// | Arguments              | Values                                                                  | Default                |
193/// |------------------------|-------------------------------------------------------------------------|------------------------|
194/// | `sampler_type` = "..." | `"filtering"`, `"non_filtering"`, `"comparison"`.                       |  `"filtering"`         |
195/// | `visibility(...)`      | `all`, `none`, or a list-combination of `vertex`, `fragment`, `compute` |   `vertex`, `fragment` |
196///
197/// ## `storage(BINDING_INDEX, arguments)`
198///
199/// * The field's [`Handle<Storage>`](bevy_asset::Handle) will be used to look
200///   up the matching [`Buffer`] GPU resource, which will be bound as a storage
201///   buffer in shaders. If the `storage` attribute is used, the field is expected
202///   a raw buffer, and the buffer will be bound as a storage buffer in shaders.
203///   In bindless mode, `binding_array()` argument that specifies the binding
204///   number of the resulting storage buffer binding array must be present.
205///
206/// | Arguments              | Values                                                                  | Default                |
207/// |------------------------|-------------------------------------------------------------------------|------------------------|
208/// | `visibility(...)`      | `all`, `none`, or a list-combination of `vertex`, `fragment`, `compute` | `vertex`, `fragment`   |
209/// | `read_only`            | if present then value is true, otherwise false                          | `false`                |
210/// | `buffer`               | if present then the field will be assumed to be a raw wgpu buffer       |                        |
211/// | `binding_array(...)`   | the binding number of the binding array, for bindless mode              | bindless mode disabled |
212///
213/// Note that fields without field-level binding attributes will be ignored.
214/// ```
215/// # use bevy_render::{render_resource::AsBindGroup};
216/// # use bevy_color::LinearRgba;
217/// # use bevy_asset::Handle;
218/// #[derive(AsBindGroup)]
219/// struct CoolMaterial {
220///     #[uniform(0)]
221///     color: LinearRgba,
222///     this_field_is_ignored: String,
223/// }
224/// ```
225///
226///  As mentioned above, [`Option<Handle<Image>>`] is also supported:
227/// ```
228/// # use bevy_asset::Handle;
229/// # use bevy_color::LinearRgba;
230/// # use bevy_image::Image;
231/// # use bevy_render::render_resource::AsBindGroup;
232/// #[derive(AsBindGroup)]
233/// struct CoolMaterial {
234///     #[uniform(0)]
235///     color: LinearRgba,
236///     #[texture(1)]
237///     #[sampler(2)]
238///     color_texture: Option<Handle<Image>>,
239/// }
240/// ```
241/// This is useful if you want a texture to be optional. When the value is [`None`], the [`crate::texture::FallbackImage`] will be used for the binding instead, which defaults
242/// to "pure white".
243///
244/// Field uniforms with the same index will be combined into a single binding:
245/// ```
246/// # use bevy_render::{render_resource::AsBindGroup};
247/// # use bevy_color::LinearRgba;
248/// #[derive(AsBindGroup)]
249/// struct CoolMaterial {
250///     #[uniform(0)]
251///     color: LinearRgba,
252///     #[uniform(0)]
253///     roughness: f32,
254/// }
255/// ```
256///
257/// In WGSL shaders, the binding would look like this:
258/// ```wgsl
259/// struct CoolMaterial {
260///     color: vec4<f32>,
261///     roughness: f32,
262/// };
263///
264/// @group(2) @binding(0) var<uniform> material: CoolMaterial;
265/// ```
266///
267/// Some less common scenarios will require "struct-level" attributes. These are the currently supported struct-level attributes:
268/// ## `uniform(BINDING_INDEX, ConvertedShaderType)`
269///
270/// * This also creates a [`Buffer`] using [`ShaderType`] and binds it as a
271///   uniform, much like the field-level `uniform` attribute. The difference is
272///   that the entire [`AsBindGroup`] value is converted to `ConvertedShaderType`,
273///   which must implement [`ShaderType`], instead of a specific field
274///   implementing [`ShaderType`]. This is useful if more complicated conversion
275///   logic is required, or when using bindless mode (see below). The conversion
276///   is done using the [`AsBindGroupShaderType<ConvertedShaderType>`] trait,
277///   which is automatically implemented if `&Self` implements
278///   [`Into<ConvertedShaderType>`]. Outside of bindless mode, only use
279///   [`AsBindGroupShaderType`] if access to resources like
280///   [`RenderAssets<GpuImage>`] is required.
281///
282/// * In bindless mode (see `bindless(COUNT)`), this attribute becomes
283///   `uniform(BINDLESS_INDEX, ConvertedShaderType,
284///   binding_array(BINDING_INDEX))`. The resulting uniform buffers will be
285///   available in the shader as a binding array at the given `BINDING_INDEX`. The
286///   `BINDLESS_INDEX` specifies the offset of the buffer in the bindless index
287///   table.
288///
289///   For example, suppose that the material slot is stored in a variable named
290///   `slot`, the bindless index table is named `material_indices`, and that the
291///   first field (index 0) of the bindless index table type is named
292///   `material`. Then specifying `#[uniform(0, StandardMaterialUniform,
293///   binding_array(10)]` will create a binding array buffer declared in the
294///   shader as `var<storage> material_array:
295///   binding_array<StandardMaterialUniform>` and accessible as
296///   `material_array[material_indices[slot].material]`.
297///
298/// ## `data(BINDING_INDEX, ConvertedShaderType, binding_array(BINDING_INDEX))`
299///
300/// * This is very similar to `uniform(BINDING_INDEX, ConvertedShaderType,
301///   binding_array(BINDING_INDEX)` and in fact is identical if bindless mode
302///   isn't being used. The difference is that, in bindless mode, the `data`
303///   attribute produces a single buffer containing an array, not an array of
304///   buffers. For example, suppose you had the following declaration:
305///
306/// ```ignore
307/// #[uniform(0, StandardMaterialUniform, binding_array(10))]
308/// struct StandardMaterial { ... }
309/// ```
310///
311/// In bindless mode, this will produce a binding matching the following WGSL
312/// declaration:
313///
314/// ```wgsl
315/// @group(2) @binding(10) var<storage> material_array: binding_array<StandardMaterial>;
316/// ```
317///
318/// On the other hand, if you write this declaration:
319///
320/// ```ignore
321/// #[data(0, StandardMaterialUniform, binding_array(10))]
322/// struct StandardMaterial { ... }
323/// ```
324///
325/// Then Bevy produces a binding that matches this WGSL declaration instead:
326///
327/// ```wgsl
328/// @group(2) @binding(10) var<storage> material_array: array<StandardMaterial>;
329/// ```
330///
331/// * Just as with the structure-level `uniform` attribute, Bevy converts the
332///   entire [`AsBindGroup`] to `ConvertedShaderType`, using the
333///   [`AsBindGroupShaderType<ConvertedShaderType>`] trait.
334///
335/// * In non-bindless mode, the structure-level `data` attribute is the same as
336///   the structure-level `uniform` attribute and produces a single uniform buffer
337///   in the shader. The above example would result in a binding that looks like
338///   this in WGSL in non-bindless mode:
339///
340/// ```wgsl
341/// @group(2) @binding(0) var<uniform> material: StandardMaterial;
342/// ```
343///
344/// * For efficiency reasons, `data` is generally preferred over `uniform`
345///   unless you need to place your data in individual buffers.
346///
347/// ## `bind_group_data(DataType)`
348///
349/// * The [`AsBindGroup`] type will be converted to some `DataType` using [`Into<DataType>`] and stored
350///   as [`AsBindGroup::Data`] as part of the [`AsBindGroup::as_bind_group`] call. This is useful if data needs to be stored alongside
351///   the generated bind group, such as a unique identifier for a material's bind group. The most common use case for this attribute
352///   is "shader pipeline specialization". See [`SpecializedRenderPipeline`](crate::render_resource::SpecializedRenderPipeline).
353///
354/// ## `bindless`
355///
356/// * This switch enables *bindless resources*, which changes the way Bevy
357///   supplies resources (textures, and samplers) to the shader.  When bindless
358///   resources are enabled, and the current platform supports them, Bevy will
359///   allocate textures, and samplers into *binding arrays*, separated based on
360///   type and will supply your shader with indices into those arrays.
361/// * Bindless textures and samplers are placed into the appropriate global
362///   array defined in `bevy_render::bindless` (`bindless.wgsl`).
363/// * Bevy doesn't currently support bindless buffers, except for those created
364///   with the `uniform(BINDLESS_INDEX, ConvertedShaderType,
365///   binding_array(BINDING_INDEX))` attribute. If you need to include a buffer in
366///   your object, and you can't create the data in that buffer with the `uniform`
367///   attribute, consider a non-bindless object instead.
368/// * If bindless mode is enabled, the `BINDLESS` definition will be
369///   available. Because not all platforms support bindless resources, you
370///   should check for the presence of this definition via `#ifdef` and fall
371///   back to standard bindings if it isn't present.
372/// * By default, in bindless mode, binding 0 becomes the *bindless index
373///   table*, which is an array of structures, each of which contains as many
374///   fields of type `u32` as the highest binding number in the structure
375///   annotated with `#[derive(AsBindGroup)]`. Again by default, the *i*th field
376///   of the bindless index table contains the index of the resource with binding
377///   *i* within the appropriate binding array.
378/// * In the case of materials, the index of the applicable table within the
379///   bindless index table list corresponding to the mesh currently being drawn
380///   can be retrieved with
381///   `mesh[in.instance_index].material_and_lightmap_bind_group_slot & 0xffffu`.
382/// * You can limit the size of the bindless slabs to N resources with the
383///   `limit(N)` declaration. For example, `#[bindless(limit(16))]` ensures that
384///   each slab will have no more than 16 total resources in it. If you don't
385///   specify a limit, Bevy automatically picks a reasonable one for the current
386///   platform.
387/// * The `index_table(range(M..N), binding(B))` declaration allows you to
388///   customize the layout of the bindless index table. This is useful for
389///   materials that are composed of multiple bind groups, such as
390///   `ExtendedMaterial`. In such cases, there will be multiple bindless index
391///   tables, so they can't both be assigned to binding 0 or their bindings will
392///   conflict.
393///   - The `binding(B)` attribute of the `index_table` attribute allows you to
394///     customize the binding (`@binding(B)`, in the shader) at which the index
395///     table will be bound.
396///   - The `range(M, N)` attribute of the `index_table` attribute allows you to
397///     change the mapping from the field index in the bindless index table to the
398///     bindless index. Instead of the field at index $i$ being mapped to the
399///     bindless index $i$, with the `range(M, N)` attribute the field at index
400///     $i$ in the bindless index table is mapped to the bindless index $i$ + M.
401///     The size of the index table will be set to N - M. Note that this may
402///     result in the table being too small to contain all the bindless bindings.
403/// * The purpose of bindless mode is to improve performance by reducing
404///   state changes. By grouping resources together into binding arrays, Bevy
405///   doesn't have to modify GPU state as often, decreasing API and driver
406///   overhead.
407/// * See the `shaders/shader_material_bindless` example for an example of how
408///   to use bindless mode. See the `shaders/extended_material_bindless` example
409///   for a more exotic example of bindless mode that demonstrates the
410///   `index_table` attribute.
411/// * The following diagram illustrates how bindless mode works using a subset
412///   of `StandardMaterial`:
413///
414/// ```text
415///      Shader Bindings                          Sampler Binding Array
416///     +----+-----------------------------+     +-----------+-----------+-----+
417/// +---|  0 | material_indices            |  +->| sampler 0 | sampler 1 | ... |
418/// |   +----+-----------------------------+  |  +-----------+-----------+-----+
419/// |   |  1 | bindless_samplers_filtering +--+        ^
420/// |   +----+-----------------------------+           +-------------------------------+
421/// |   | .. |            ...              |                                           |
422/// |   +----+-----------------------------+      Texture Binding Array                |
423/// |   |  5 | bindless_textures_2d        +--+  +-----------+-----------+-----+       |
424/// |   +----+-----------------------------+  +->| texture 0 | texture 1 | ... |       |
425/// |   | .. |            ...              |     +-----------+-----------+-----+       |
426/// |   +----+-----------------------------+           ^                               |
427/// |   + 10 | material_array              +--+        +---------------------------+   |
428/// |   +----+-----------------------------+  |                                    |   |
429/// |                                         |   Buffer Binding Array             |   |
430/// |                                         |  +----------+----------+-----+     |   |
431/// |                                         +->| buffer 0 | buffer 1 | ... |     |   |
432/// |    Material Bindless Indices               +----------+----------+-----+     |   |
433/// |   +----+-----------------------------+          ^                            |   |
434/// +-->|  0 | material                    +----------+                            |   |
435///     +----+-----------------------------+                                       |   |
436///     |  1 | base_color_texture          +---------------------------------------+   |
437///     +----+-----------------------------+                                           |
438///     |  2 | base_color_sampler          +-------------------------------------------+
439///     +----+-----------------------------+
440///     | .. |            ...              |
441///     +----+-----------------------------+
442/// ```
443///
444/// The previous `CoolMaterial` example illustrating "combining multiple field-level uniform attributes with the same binding index" can
445/// also be equivalently represented with a single struct-level uniform attribute:
446/// ```
447/// # use bevy_render::{render_resource::{AsBindGroup, ShaderType}};
448/// # use bevy_color::LinearRgba;
449/// #[derive(AsBindGroup)]
450/// #[uniform(0, CoolMaterialUniform)]
451/// struct CoolMaterial {
452///     color: LinearRgba,
453///     roughness: f32,
454/// }
455///
456/// #[derive(ShaderType)]
457/// struct CoolMaterialUniform {
458///     color: LinearRgba,
459///     roughness: f32,
460/// }
461///
462/// impl From<&CoolMaterial> for CoolMaterialUniform {
463///     fn from(material: &CoolMaterial) -> CoolMaterialUniform {
464///         CoolMaterialUniform {
465///             color: material.color,
466///             roughness: material.roughness,
467///         }
468///     }
469/// }
470/// ```
471///
472/// Setting `bind_group_data` looks like this:
473/// ```
474/// # use bevy_render::{render_resource::AsBindGroup};
475/// # use bevy_color::LinearRgba;
476/// #[derive(AsBindGroup)]
477/// #[bind_group_data(CoolMaterialKey)]
478/// struct CoolMaterial {
479///     #[uniform(0)]
480///     color: LinearRgba,
481///     is_shaded: bool,
482/// }
483///
484/// #[derive(Copy, Clone, Hash, Eq, PartialEq)]
485/// struct CoolMaterialKey {
486///     is_shaded: bool,
487/// }
488///
489/// impl From<&CoolMaterial> for CoolMaterialKey {
490///     fn from(material: &CoolMaterial) -> CoolMaterialKey {
491///         CoolMaterialKey {
492///             is_shaded: material.is_shaded,
493///         }
494///     }
495/// }
496/// ```
497pub trait AsBindGroup {
498    /// Data that will be stored alongside the "prepared" bind group.
499    type Data: Send + Sync;
500
501    type Param: SystemParam + 'static;
502
503    /// The number of slots per bind group, if bindless mode is enabled.
504    ///
505    /// If this bind group doesn't use bindless, then this will be `None`.
506    ///
507    /// Note that the *actual* slot count may be different from this value, due
508    /// to platform limitations. For example, if bindless resources aren't
509    /// supported on this platform, the actual slot count will be 1.
510    fn bindless_slot_count() -> Option<BindlessSlabResourceLimit> {
511        None
512    }
513
514    /// True if the hardware *actually* supports bindless textures for this
515    /// type, taking the device and driver capabilities into account.
516    ///
517    /// If this type doesn't use bindless textures, then the return value from
518    /// this function is meaningless.
519    fn bindless_supported(_: &RenderDevice) -> bool {
520        true
521    }
522
523    /// label
524    fn label() -> Option<&'static str> {
525        None
526    }
527
528    /// Creates a bind group for `self` matching the layout defined in [`AsBindGroup::bind_group_layout`].
529    fn as_bind_group(
530        &self,
531        layout: &BindGroupLayout,
532        render_device: &RenderDevice,
533        param: &mut SystemParamItem<'_, '_, Self::Param>,
534    ) -> Result<PreparedBindGroup<Self::Data>, AsBindGroupError> {
535        let UnpreparedBindGroup { bindings, data } =
536            Self::unprepared_bind_group(self, layout, render_device, param, false)?;
537
538        let entries = bindings
539            .iter()
540            .map(|(index, binding)| BindGroupEntry {
541                binding: *index,
542                resource: binding.get_binding(),
543            })
544            .collect::<Vec<_>>();
545
546        let bind_group = render_device.create_bind_group(Self::label(), layout, &entries);
547
548        Ok(PreparedBindGroup {
549            bindings,
550            bind_group,
551            data,
552        })
553    }
554
555    /// Returns a vec of (binding index, `OwnedBindingResource`).
556    ///
557    /// In cases where `OwnedBindingResource` is not available (as for bindless
558    /// texture arrays currently), an implementor may return
559    /// `AsBindGroupError::CreateBindGroupDirectly` from this function and
560    /// instead define `as_bind_group` directly. This may prevent certain
561    /// features, such as bindless mode, from working correctly.
562    ///
563    /// Set `force_no_bindless` to true to require that bindless textures *not*
564    /// be used. `ExtendedMaterial` uses this in order to ensure that the base
565    /// material doesn't use bindless mode if the extension doesn't.
566    fn unprepared_bind_group(
567        &self,
568        layout: &BindGroupLayout,
569        render_device: &RenderDevice,
570        param: &mut SystemParamItem<'_, '_, Self::Param>,
571        force_no_bindless: bool,
572    ) -> Result<UnpreparedBindGroup<Self::Data>, AsBindGroupError>;
573
574    /// Creates the bind group layout matching all bind groups returned by
575    /// [`AsBindGroup::as_bind_group`]
576    fn bind_group_layout(render_device: &RenderDevice) -> BindGroupLayout
577    where
578        Self: Sized,
579    {
580        render_device.create_bind_group_layout(
581            Self::label(),
582            &Self::bind_group_layout_entries(render_device, false),
583        )
584    }
585
586    /// Returns a vec of bind group layout entries.
587    ///
588    /// Set `force_no_bindless` to true to require that bindless textures *not*
589    /// be used. `ExtendedMaterial` uses this in order to ensure that the base
590    /// material doesn't use bindless mode if the extension doesn't.
591    fn bind_group_layout_entries(
592        render_device: &RenderDevice,
593        force_no_bindless: bool,
594    ) -> Vec<BindGroupLayoutEntry>
595    where
596        Self: Sized;
597
598    fn bindless_descriptor() -> Option<BindlessDescriptor> {
599        None
600    }
601}
602
603/// An error that occurs during [`AsBindGroup::as_bind_group`] calls.
604#[derive(Debug, Error)]
605pub enum AsBindGroupError {
606    /// The bind group could not be generated. Try again next frame.
607    #[error("The bind group could not be generated")]
608    RetryNextUpdate,
609    #[error("Create the bind group via `as_bind_group()` instead")]
610    CreateBindGroupDirectly,
611    #[error("At binding index {0}, the provided image sampler `{1}` does not match the required sampler type(s) `{2}`.")]
612    InvalidSamplerType(u32, String, String),
613}
614
615/// A prepared bind group returned as a result of [`AsBindGroup::as_bind_group`].
616pub struct PreparedBindGroup<T> {
617    pub bindings: BindingResources,
618    pub bind_group: BindGroup,
619    pub data: T,
620}
621
622/// a map containing `OwnedBindingResource`s, keyed by the target binding index
623pub struct UnpreparedBindGroup<T> {
624    pub bindings: BindingResources,
625    pub data: T,
626}
627
628/// A pair of binding index and binding resource, used as part of
629/// [`PreparedBindGroup`] and [`UnpreparedBindGroup`].
630#[derive(Deref, DerefMut)]
631pub struct BindingResources(pub Vec<(u32, OwnedBindingResource)>);
632
633/// An owned binding resource of any type (ex: a [`Buffer`], [`TextureView`], etc).
634/// This is used by types like [`PreparedBindGroup`] to hold a single list of all
635/// render resources used by bindings.
636#[derive(Debug)]
637pub enum OwnedBindingResource {
638    Buffer(Buffer),
639    TextureView(TextureViewDimension, TextureView),
640    Sampler(SamplerBindingType, Sampler),
641    Data(OwnedData),
642}
643
644/// Data that will be copied into a GPU buffer.
645///
646/// This corresponds to the `#[data]` attribute in `AsBindGroup`.
647#[derive(Debug, Deref, DerefMut)]
648pub struct OwnedData(pub Vec<u8>);
649
650impl OwnedBindingResource {
651    /// Creates a [`BindingResource`] reference to this
652    /// [`OwnedBindingResource`].
653    ///
654    /// Note that this operation panics if passed a
655    /// [`OwnedBindingResource::Data`], because [`OwnedData`] doesn't itself
656    /// correspond to any binding and instead requires the
657    /// `MaterialBindGroupAllocator` to pack it into a buffer.
658    pub fn get_binding(&self) -> BindingResource {
659        match self {
660            OwnedBindingResource::Buffer(buffer) => buffer.as_entire_binding(),
661            OwnedBindingResource::TextureView(_, view) => BindingResource::TextureView(view),
662            OwnedBindingResource::Sampler(_, sampler) => BindingResource::Sampler(sampler),
663            OwnedBindingResource::Data(_) => panic!("`OwnedData` has no binding resource"),
664        }
665    }
666}
667
668/// Converts a value to a [`ShaderType`] for use in a bind group.
669///
670/// This is automatically implemented for references that implement [`Into`].
671/// Generally normal [`Into`] / [`From`] impls should be preferred, but
672/// sometimes additional runtime metadata is required.
673/// This exists largely to make some [`AsBindGroup`] use cases easier.
674pub trait AsBindGroupShaderType<T: ShaderType> {
675    /// Return the `T` [`ShaderType`] for `self`. When used in [`AsBindGroup`]
676    /// derives, it is safe to assume that all images in `self` exist.
677    fn as_bind_group_shader_type(&self, images: &RenderAssets<GpuImage>) -> T;
678}
679
680impl<T, U: ShaderType> AsBindGroupShaderType<U> for T
681where
682    for<'a> &'a T: Into<U>,
683{
684    #[inline]
685    fn as_bind_group_shader_type(&self, _images: &RenderAssets<GpuImage>) -> U {
686        self.into()
687    }
688}
689
690#[cfg(test)]
691mod test {
692    use super::*;
693    use bevy_asset::Handle;
694    use bevy_image::Image;
695
696    #[test]
697    fn texture_visibility() {
698        #[derive(AsBindGroup)]
699        pub struct TextureVisibilityTest {
700            #[texture(0, visibility(all))]
701            pub all: Handle<Image>,
702            #[texture(1, visibility(none))]
703            pub none: Handle<Image>,
704            #[texture(2, visibility(fragment))]
705            pub fragment: Handle<Image>,
706            #[texture(3, visibility(vertex))]
707            pub vertex: Handle<Image>,
708            #[texture(4, visibility(compute))]
709            pub compute: Handle<Image>,
710            #[texture(5, visibility(vertex, fragment))]
711            pub vertex_fragment: Handle<Image>,
712            #[texture(6, visibility(vertex, compute))]
713            pub vertex_compute: Handle<Image>,
714            #[texture(7, visibility(fragment, compute))]
715            pub fragment_compute: Handle<Image>,
716            #[texture(8, visibility(vertex, fragment, compute))]
717            pub vertex_fragment_compute: Handle<Image>,
718        }
719    }
720}