Module vulkano::descriptor

Collection of data and resources accessed by the shaders.

In order to read the content of a buffer or an image from a shader, that buffer or image must be put in a descriptor. Each descriptor contains one or several buffers or images alongside with the way that it can be accessed.

Descriptors are grouped in what is called descriptor sets. In Vulkan you don't bind individual descriptors one by one, but you bind descriptor sets one by one. Therefore you are encouraged to put descriptors that are often used together in the same set.

In addition to descriptors, you also have the possibility to feed raw data to your shaders. Each variable that you pass to a shader is called a push constant.

The layout of all the descriptors and the push constants used by a pipeline is grouped in a pipeline layout.

Pipeline initialization

When you build a pipeline object (a GraphicsPipeline or a ComputePipeline), you have to pass a pointer to a struct that implements the PipelineLayout trait. This object will describe to the Vulkan implementation the types and layouts of the descriptors and push constants that are going to be accessed by the shaders of the pipeline.

The PipelineLayout trait is unsafe. You are encouraged not to implemented it yourself, but instead use one of the already-existing implementations that are available to you:

• The shader analyser (from the vulkano-shaders crate) will generate an object named Layout for each shader module.
• You can merge multiple implementations of PipelineLayout into one with the merge_pipelines! macro.
• You can create a pipeline layout whose content is only known at runtime with the Foo object. This is the most costly solution, as vulkano will need to perform runtime checks.

Descriptor sets

When you draw, you have to pass two parameters (two parameters that are relevant here): the list of descriptor sets to use, and the push constants. Vulkano will check that what you passed is compatible with the pipeline layout that you used when creating the pipeline.

Descriptor sets have to be created in advance from a descriptor pool. You can use the same descriptor set multiple time with multiple draw commands, and keep alive descriptor sets between frames. Creating a descriptor set is quite cheap, so it won't kill your performances to create new sets at each frame.

TODO: talk about perfs of changing sets

Reexports

pub use self::descriptor_set::DescriptorSet;

Modules

descriptor
descriptor_set
pipeline_layout	Describes the layout of descriptors and push constants used by a pipeline.

Traits

PipelineLayout

Trait for objects that describe the layout of the descriptors and push constants of a pipeline.