Alloy is a tiny set of utils and extensions over Apple's Metal framework dedicated to make your Swift GPU code much cleaner and let you prototype your pipelines faster.
While this library doesn't introduce any new paradigms or concepts that significantly change the way you approach your Metal implementations, it has some optional-to-use things that you can incorporate in your apps if you find them as useful as library author did :)
- Nano-tiny layer over vanilla Metal API
- No external dependencies
- Cross-platform support
- Very Swifty
Combine the power of CoreGraphics and Metal by sharing resource memory
First of all, this framework provides a set of utils, that hides the majority of redudant explicity in your Metal code, while not limiting a flexibility a bit. You can easily mix Alloy and vanilla Metal code.
The only new concept that Alloy introduces is MTLContext. Internally this is meant to store objects that are usually being shared and injected across your app.
In particular, this is:
- device:
MTLDevice - commandQueue:
MTLCommandQueue - standardLibrary:
MTLLibrary?
Internally, it also manages a MTKTextureLoader and a cache of MTLLibraries, but this logic should be considered private. As of now, MTLContext is not threadsafe.
MTLContext usually being injected as a dependency to any object that interacts with Metal devices.
It can do a bunch of things for you, few examples:
let texture = context.texture(from: cgImage,
usage: [.shaderRead, .shaderWrite])See how you can group encodings with Swift closures.
self.context.scheduleAndWait { buffer in
buffer.compute { encoder in
// compute command encoding logic
}
buffer.blit { encoder in
// blit command encoding logic
}
}let lib = context.shaderLibrary(for: Foo.self)
let computePipelineState = try? lib.computePipelineState(function: "brightness")let buffer = context.buffer(for: InstanceUniforms.self,
count: 99,
options: .storageModeShared)let encoder = JSONEncoder()
let data = try encoder.encode(texture.codable())
let decoder = JSONDecoder()
let decodableTexture = try decoder.decode(MTLTextureCodableBox.self, from: data)
let decodedTexture = try decodableTexture.texture(device: self.context.device)- Create multi-sample render target pairs
- Create textures
- Create depth buffers
- Create depth/stencil states
- etc
Other types that are introduces my Alloy are
MTLOffscreenRenderer: this is a class that lets you create simple off-screen renderers to draw something into arbitaryMTLTexturesComputeCommand: this is an experimental class that does a reflection over Metal kernels and lets you assign arguments by name instead of index. This is a subject for improvements.BlendingMode: this type contains the enumeration of eight Alloy's built-in blending modes. You can easily setup one of them just by callingsetup(blending:)function.let renderPipelineDescriptor = MTLRenderPipelineDescriptor() renderPipelineDescriptor.colorAttachments[0].setup(blending: .alpha)
MTLContext is usually being injected in the class, as you usually do with MTLDevice, you should cache the context and all heavy-weighted objects so you can reuse them lates, i.e.:
import Alloy
public class BrightnessEncoder {
public let context: MTLContext
fileprivate let pipelineState: MTLComputePipelineState
/**
* This variable controls the brightness factor. Should be in range of -1.0...1.0
*/
public var intensity: Float = 1.0
public init(context: MTLContext) {
self.context = context
guard let lib = context.shaderLibrary(for: BrightnessEncoder.self),
let state = try? lib.computePipelineState(function: "brightness")
else { fatalError("Error during shader loading") }
self.pipelineState = state
}
public func encode(input: MTLTexture,
in commandBuffer: MTLCommandBuffer) {
commandBuffer.compute { encoder in
encoder.set(textures: [input])
encoder.set(self.intensity, at: 0)
encoder.dispatch2d(state: self.pipelineState,
covering: input.size)
}
}
}Note how simple it is to kick off a kernel with Alloy, no more tedious thredgroup size calculations, multiple encoder initialization with balancing .endEncoding() calls.
Then somewhere else you just do
context.scheduleAndWait { buffer in
self.brightnessEncoder.intensity = sender.floatValue
self.brightnessEncoder.encode(input: texture,
in: buffer)
// For Mac applications
if case .managed = texture.storageMode {
buffer.blit { encoder in
encoder.synchronize(resource: texture)
}
}
}With this approach you can easily stack and build your GPU pipeline layers, group blit, compute and render command encodings with Swift closures, while maintaing full flexibility of Metal API.
CocoaPods is a dependency manager for Cocoa projects. For usage and installation instructions, visit their website. To integrate Alloy into your Xcode project using CocoaPods, specify it in your Podfile:
# Optionally add version, i.e. '~> 0.9.0'
pod 'Alloy'MIT