40 releases (3 stable)
23.0.1 | Nov 25, 2024 |
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22.0.0 | Jul 18, 2024 |
0.21.1 | Jun 26, 2024 |
0.19.3 |
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0.0.1 | Jul 15, 2021 |
#273 in Graphics APIs
300,584 downloads per month
Used in 1,687 crates
(7 directly)
5MB
105K
SLoC
wgpu_hal
: a cross-platform unsafe graphics abstraction
This crate defines a set of traits abstracting over modern graphics APIs, with implementations ("backends") for Vulkan, Metal, Direct3D, and GL.
wgpu_hal
is a spiritual successor to
gfx-hal, but with reduced scope, and
oriented towards WebGPU implementation goals. It has no overhead for
validation or tracking, and the API translation overhead is kept to the bare
minimum by the design of WebGPU. This API can be used for resource-demanding
applications and engines.
The wgpu_hal
crate's main design choices:
-
Our traits are meant to be portable: proper use should get equivalent results regardless of the backend.
-
Our traits' contracts are unsafe: implementations perform minimal validation, if any, and incorrect use will often cause undefined behavior. This allows us to minimize the overhead we impose over the underlying graphics system. If you need safety, the
wgpu-core
crate provides a safe API for drivingwgpu_hal
, implementing all necessary validation, resource state tracking, and so on. (Note thatwgpu-core
is designed for use via FFI; thewgpu
crate provides more idiomatic Rust bindings forwgpu-core
.) Or, you can do your own validation. -
In the same vein, returned errors only cover cases the user can't anticipate, like running out of memory or losing the device. Any errors that the user could reasonably anticipate are their responsibility to avoid. For example,
wgpu_hal
returns no error for mapping a buffer that's not mappable: as the buffer creator, the user should already know if they can map it. -
We use static dispatch. The traits are not generally object-safe. You must select a specific backend type like
vulkan::Api
ormetal::Api
, and then use that according to the main traits, or call backend-specific methods. -
We use idiomatic Rust parameter passing, taking objects by reference, returning them by value, and so on, unlike
wgpu-core
, which refers to objects by ID. -
We map buffer contents persistently. This means that the buffer can remain mapped on the CPU while the GPU reads or writes to it. You must explicitly indicate when data might need to be transferred between CPU and GPU, if
wgpu_hal
indicates that the mapping is not coherent (that is, automatically synchronized between the two devices). -
You must record explicit barriers between different usages of a resource. For example, if a buffer is written to by a compute shader, and then used as and index buffer to a draw call, you must use
CommandEncoder::transition_buffers
between those two operations. -
Pipeline layouts are explicitly specified when setting bind group. Incompatible layouts disturb groups bound at higher indices.
-
The API accepts collections as iterators, to avoid forcing the user to store data in particular containers. The implementation doesn't guarantee that any of the iterators are drained, unless stated otherwise by the function documentation. For this reason, we recommend that iterators don't do any mutating work.
Unfortunately, wgpu_hal
's safety requirements are not fully documented.
Ideally, all trait methods would have doc comments setting out the
requirements users must meet to ensure correct and portable behavior. If you
are aware of a specific requirement that a backend imposes that is not
ensured by the traits' documented rules, please file an issue. Or, if you are
a capable technical writer, please file a pull request!
Primary backends
The wgpu_hal
crate has full-featured backends implemented on the following
platform graphics APIs:
-
Vulkan, available on Linux, Android, and Windows, using the
ash
crate's Vulkan bindings. It's also available on macOS, if you install MoltenVK. -
Metal on macOS, using the
metal
crate's bindings. -
Direct3D 12 on Windows, using the
d3d12
crate's bindings.
Secondary backends
The wgpu_hal
crate has a partial implementation based on the following
platform graphics API:
- The GL backend is available anywhere OpenGL, OpenGL ES, or WebGL are
available. See the
gles
module documentation for details.
You can see what capabilities an adapter is missing by checking the
DownlevelCapabilities
in ExposedAdapter::capabilities
, available
from Instance::enumerate_adapters
.
The API is generally designed to fit the primary backends better than the secondary backends, so the latter may impose more overhead.
Debugging
Most of the information on the wiki Debugging wgpu Applications
page still applies to this API, with the exception of API tracing/replay
functionality, which is only available in wgpu-core
.
Dependencies
~3–47MB
~749K SLoC