added chapter 18

README.md

@@ -19,3 +19,4 @@ Repository to accompany the following blog posts:
 - [Using MetalKit part 15](http://mhorga.org/2016/06/23/using-metalkit-part-15.html)
 - [Using MetalKit part 16](http://mhorga.org/2016/07/06/using-metalkit-part-16.html)
 - [Using MetalKit part 17](http://mhorga.org/2016/09/24/using-metalkit-part-17.html)
+- [Using MetalKit part 18](http://mhorga.org/2016/09/30/using-metalkit-part-2-3-2.html)

chapter18.playground/Contents.swift

@@ -0,0 +1,45 @@
+
+
+let shader =    
+"#include <metal_stdlib>\n" +
+    "using namespace metal;" +
+    "kernel void k(texture2d<float,access::write> o[[texture(0)]]," +
+    "              uint2 gid[[thread_position_in_grid]]) {" +
+    "   int width = o.get_width();" +
+    "   int height = o.get_height();" +
+    "   float2 uv = float2(gid) / float2(width, height);" +
+    "   float3 color = mix(float3(1.0, 0.6, 0.1), float3(0.5, 0.8, 1.0), sqrt(1 - uv.y));" +
+    "   float2 q = uv - float2(0.67, 0.25);" +
+    "   float r = 0.2 + 0.1 * cos(atan2(q.x, q.y) * 9.0 + 20.0 * q.x);" +
+    "   color *= smoothstep(r, r + 0.01, length(q));" +
+    "   r = 0.03 + 0.002 * cos(120.0 * q.y) + exp(-50.0 * (1.0 - uv.y));" +
+    "   color *= 1.0 - (1.0 - smoothstep(r, r + 0.002, abs(q.x - 0.25 * sin(2.0 * q.y)))) * smoothstep(0.0, 0.1, q.y);" +
+    "   o.write(float4(color, 1.0), gid);" +
+"}"
+
+//"#include <metal_stdlib>\n" +
+//    "using namespace metal;" +
+//    "kernel void k(texture2d<float,access::write> o[[texture(0)]]," +
+//    "              uint2 gid[[thread_position_in_grid]]) {" +
+//    "   int width = o.get_width();" +
+//    "   int height = o.get_height();" +
+//    "   float2 uv = float2(gid) / float2(width, height);" +
+//    "   float2 q = uv - float2(0.5);" +
+//    "   float a = atan2(q.y, q.x) + 0.25;" +
+//    "   float s = 0.5 + 0.5 * sin(3.0 * a);" +
+//    "   float t = 0.15 + 0.5 * pow(s, 0.3) + 0.1 * pow(0.5 + 0.5 * cos(6.0 * a), 0.5);" +
+//    "   float h = sqrt(dot(q, q)) / t;" +
+//    "   float f = 0.0;" +
+//    "   if(h < 0.4) f = 1.0;" +
+//    "   float3 color = mix(float3(0.9), float3(0.5 * h, 0.5 + 0.5 * h, 0.0), f);" +
+//    "   o.write(float4(color, 1.0), gid);" +
+//"}"
+
+import MetalKit
+import PlaygroundSupport
+
+let frame = CGRect(x: 0, y: 0, width: 300, height: 300)
+let view = MTKView(frame: frame)
+let delegate = MetalView(mtkView: view, shader: shader)
+view.delegate = delegate
+PlaygroundPage.current.liveView = view

chapter18.playground/Sources/MetalView.swift

@@ -0,0 +1,40 @@
+
+import MetalKit
+
+public class MetalView: NSObject, MTKViewDelegate {
+    weak var view: MTKView!
+    let commandQueue: MTLCommandQueue
+    let device: MTLDevice
+    let cps: MTLComputePipelineState
+
+    public init?(mtkView: MTKView, shader: String) {
+        view = mtkView
+        view.clearColor = MTLClearColorMake(0.5, 0.5, 0.5, 1)
+        view.colorPixelFormat = .bgra8Unorm
+        device = MTLCreateSystemDefaultDevice()!
+        commandQueue = device.makeCommandQueue()
+        let library = try! device.makeLibrary(source: shader, options: nil)
+        let function = library.makeFunction(name:"k")!
+        cps = try! device.makeComputePipelineState(function: function)
+
+        super.init()
+        view.delegate = self
+        view.device = device
+    }
+
+    public func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {}
+
+    public func draw(in view: MTKView) {
+        let drawable = view.currentDrawable!
+        let commandBuffer = commandQueue.makeCommandBuffer()
+        let commandEncoder = commandBuffer.makeComputeCommandEncoder()
+        commandEncoder.setComputePipelineState(cps)
+        commandEncoder.setTexture(drawable.texture, at: 0)
+        let groups = MTLSize(width: Int(view.frame.width)/4, height: Int(view.frame.height)/4, depth: 1)
+        let threads = MTLSize(width: 8, height: 8,depth: 1)
+        commandEncoder.dispatchThreadgroups(groups,threadsPerThreadgroup: threads)
+        commandEncoder.endEncoding()
+        commandBuffer.present(drawable)
+        commandBuffer.commit()
+    }
+}

chapter18.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos' executeOnSourceChanges='false'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

chapter18.playground/timeline.xctimeline

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>