terrain/Terrain2/Algorithms.swift

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//
// Algorithms.swift
// Terrain2
//
// Created by Eryn Wells on 11/4/18.
// Copyright © 2018 Eryn Wells. All rights reserved.
//
import Foundation
import Metal
enum KernelError: Error {
case badFunction
case textureCreationFailed
}
protocol Algorithm {
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var name: String { get }
var outTexture: MTLTexture { get }
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func updateUniforms()
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func encode(in encoder: MTLComputeCommandEncoder)
}
class Kernel {
static let textureSize = MTLSize(width: 512, height: 512, depth: 1)
class func buildTexture(device: MTLDevice, size: MTLSize) -> MTLTexture? {
let desc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .r32Float, width: size.width, height: size.height, mipmapped: false)
desc.usage = [.shaderRead, .shaderWrite]
let tex = device.makeTexture(descriptor: desc)
return tex
}
let pipeline: MTLComputePipelineState
let textures: [MTLTexture]
let uniformBuffer: MTLBuffer?
var outTexture: MTLTexture {
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return textures[textureIndexes.out]
}
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private(set) var textureIndexes: (`in`: Int, out: Int) = (in: 0, out: 1)
init(device: MTLDevice, library: MTLLibrary, functionName: String, uniformBuffer: MTLBuffer? = nil) throws {
guard let computeFunction = library.makeFunction(name: functionName) else {
throw KernelError.badFunction
}
self.pipeline = try device.makeComputePipelineState(function: computeFunction)
// Create our input and output textures
var textures = [MTLTexture]()
for i in 0..<2 {
guard let tex = Kernel.buildTexture(device: device, size: Kernel.textureSize) else {
print("Couldn't create heights texture i=\(i)")
throw KernelError.textureCreationFailed
}
textures.append(tex)
}
self.textures = textures
self.uniformBuffer = uniformBuffer
}
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func encode(in encoder: MTLComputeCommandEncoder) {
encoder.setComputePipelineState(pipeline)
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encoder.setTexture(textures[textureIndexes.in], index: textureIndexes.in)
encoder.setTexture(textures[textureIndexes.out], index: textureIndexes.out)
encoder.setBuffer(uniformBuffer, offset: 0, index: 0)
encoder.dispatchThreads(Kernel.textureSize, threadsPerThreadgroup: MTLSize(width: 8, height: 8, depth: 1))
}
}
/// "Compute" zero for every value of the height map.
class ZeroAlgorithm: Kernel, Algorithm {
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let name = "Zero"
init?(device: MTLDevice, library: MTLLibrary) {
do {
try super.init(device: device, library: library, functionName: "zeroKernel")
} catch let e {
print("Couldn't create compute kernel. Error: \(e)")
return nil
}
}
// MARK: Algorithm
func updateUniforms() { }
}
/// Randomly generate heights that are independent of all others.
class RandomAlgorithm: Kernel, Algorithm {
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let name = "Random"
private var uniforms: UnsafeMutablePointer<RandomAlgorithmUniforms>
init?(device: MTLDevice, library: MTLLibrary) {
let bufferSize = (MemoryLayout<RandomAlgorithmUniforms>.stride & ~0xFF) + 0x100;
guard let buffer = device.makeBuffer(length: bufferSize, options: [.storageModeShared]) else {
print("Couldn't create uniform buffer")
return nil
}
uniforms = UnsafeMutableRawPointer(buffer.contents()).bindMemory(to: RandomAlgorithmUniforms.self, capacity:1)
do {
try super.init(device: device, library: library, functionName: "randomKernel", uniformBuffer: buffer)
} catch let e {
print("Couldn't create compute kernel. Error: \(e)")
return nil
}
updateUniforms()
}
func updateUniforms() {
RandomAlgorithmUniforms_refreshRandoms(uniforms)
}
}
/// Implementation of the Diamond-Squares algorithm.
/// - https://en.wikipedia.org/wiki/Diamond-square_algorithm
//class DiamondSquareAlgorithm: Algorithm {
// static let name = "Diamond-Square"
//}
/// Implementation of the Circles algorithm.
//class CirclesAlgorithm: Algorithm {
// static let name = "Circles"
//}