Module vulkano::descriptor_set [−][src]
Expand description
Bindings between shaders and the resources they access.
Overview
In order to access a buffer or an image from a shader, that buffer or image must be put in a descriptor. Each descriptor contains one buffer or one image alongside with the way that it can be accessed. A descriptor can also be an array, in which case it contains multiple buffers or images that all have the same layout.
Descriptors are grouped in what is called descriptor sets. In Vulkan you don’t bind individual descriptors one by one, but you create then bind descriptor sets one by one. As binding a descriptor set has (small but non-null) a cost, you are encouraged to put descriptors that are often used together in the same set so that you can keep the same set binding through multiple draws.
Example
Note: This section describes the simple way to bind resources. There are more optimized ways.
There are two steps to give access to a resource in a shader: creating the descriptor set, and passing the descriptor sets when drawing.
Creating a descriptor set
TODO: write example for: PersistentDescriptorSet::start(layout.clone()).add_buffer(data_buffer.clone())
Passing the descriptor set when drawing
TODO: write
When drawing
When you call a function that adds a draw command to a command buffer, one of the parameters corresponds to the list of descriptor sets to use. Vulkano will check that what you passed is compatible with the layout of the pipeline.
TODO: talk about perfs of changing sets
Descriptor sets creation and management
There are three concepts in Vulkan related to descriptor sets:
- A
DescriptorSetLayout
is a Vulkan object that describes to the Vulkan implementation the layout of a future descriptor set. When you allocate a descriptor set, you have to pass an instance of this object. This is represented with theDescriptorSetLayout
type in vulkano. - A
DescriptorPool
is a Vulkan object that holds the memory of descriptor sets and that can be used to allocate and free individual descriptor sets. This is represented with theUnsafeDescriptorPool
type in vulkano. - A
DescriptorSet
contains the bindings to resources and is allocated from a pool. This is represented with theUnsafeDescriptorSet
type in vulkano.
In addition to this, vulkano defines the following:
- The
DescriptorPool
trait can be implemented on types from which you can allocate and free descriptor sets. However it is different from Vulkan descriptor pools in the sense that an implementation of theDescriptorPool
trait can manage multiple Vulkan descriptor pools. - The
StdDescriptorPool
type is a default implementation of theDescriptorPool
trait. - The
DescriptorSet
trait is implemented on types that wrap around Vulkan descriptor sets in a safe way. A Vulkan descriptor set is inherently unsafe, so we need safe wrappers around them. - The
SimpleDescriptorSet
type is a default implementation of theDescriptorSet
trait. - The
DescriptorSetsCollection
trait is implemented on collections of types that implementDescriptorSet
. It is what you pass to the draw functions.
Re-exports
pub use self::fixed_size_pool::FixedSizeDescriptorSetsPool;
pub use self::persistent::PersistentDescriptorSet;
pub use self::persistent::PersistentDescriptorSetBuildError;
pub use self::persistent::PersistentDescriptorSetError;
Modules
Pool of descriptor sets of a specific capacity that are automatically reclaimed.
Describes the layout of all descriptors within a descriptor set.
A simple, immutable descriptor set that is expected to be long-lived.
A pool from which descriptor sets can be allocated.
Low-level descriptor set.
Structs
Traits
Trait for objects that contain a collection of resources that will be accessible by shaders.
A collection of descriptor set objects.