added chapter 15

README.md

@@ -15,4 +15,5 @@ Repository to accompany the following blog posts:
 - [Using MetalKit part 11](http://mhorga.org/2016/05/10/using-metalkit-part-11.html)
 - [Using MetalKit part 12](http://mhorga.org/2016/05/18/using-metalkit-part-12.html)
 - [Using MetalKit part 13](http://mhorga.org/2016/05/25/using-metalkit-part-13.html)
-- [Using MetalKit part 14](http://mhorga.org/2016/06/01/using-metalkit-part-14.html)
+- [Using MetalKit part 14](http://mhorga.org/2016/06/01/using-metalkit-part-14.html)
+- [Using MetalKit part 15](http://mhorga.org/2016/06/23/using-metalkit-part-15.html)

ch15/chapter15.playground/Contents.swift

@@ -0,0 +1,8 @@
+
+import Cocoa
+import XCPlayground
+
+let device = MTLCreateSystemDefaultDevice()!
+let frame = NSRect(x:0, y:0, width:400, height:400)
+let view = MetalView(frame: frame, device: device)
+XCPlaygroundPage.currentPage.liveView = view

ch15/chapter15.playground/Resources/Shaders.metal

@@ -0,0 +1,30 @@
+
+#include <metal_stdlib>
+
+using namespace metal;
+
+kernel void compute(texture2d<float, access::write> output [[texture(0)]],
+                    texture2d<float, access::sample> input [[texture(1)]],
+                    constant float &timer [[buffer(0)]],
+                    uint2 gid [[thread_position_in_grid]])
+{
+  int width = input.get_width();
+  int height = input.get_height();
+  float2 uv = float2(gid) / float2(width, height);
+  uv = uv * 2.0 - 1.0;
+  uv = uv * 2;
+  float radius = 1;
+  float distance = length(uv) - radius;
+  constexpr sampler textureSampler(coord::normalized,
+                                   address::repeat,
+                                   min_filter::linear,
+                                   mag_filter::linear,
+                                   mip_filter::linear );
+  float3 norm = float3(uv, sqrt(1.0 - dot(uv, uv)));
+  float pi = 3.14;
+  float s = atan2( norm.z, norm.x ) / (2 * pi);
+  float t = asin( norm.y ) / (2 * pi);
+  t += 0.5;
+  float4 color = input.sample(textureSampler, float2(s + timer * 0.1, t));
+  output.write(distance < 0 ? color : float4(0), gid);
+}

ch15/chapter15.playground/Sources/MetalView.swift

@@ -0,0 +1,66 @@
+
+import MetalKit
+
+public class MetalView: MTKView, NSWindowDelegate {
+    
+    var queue: MTLCommandQueue! = nil
+    var cps: MTLComputePipelineState! = nil
+    var timer: Float = 0
+    var timerBuffer: MTLBuffer!
+    var texture: MTLTexture!
+  
+    required public init(coder: NSCoder) {
+        super.init(coder: coder)
+    }
+    
+    override public init(frame frameRect: CGRect, device: MTLDevice?) {
+        super.init(frame: frameRect, device: device)
+        registerShaders()
+        setUpTexture()
+    }
+  
+    func setUpTexture() {
+        let path = NSBundle.mainBundle().pathForResource("texture", ofType: "jpg")
+        let textureLoader = MTKTextureLoader(device: device!)
+        texture = try! textureLoader.newTextureWithContentsOfURL(NSURL(fileURLWithPath: path!), options: nil)
+    }
+  
+    override public func drawRect(dirtyRect: NSRect) {
+        if let drawable = currentDrawable {
+            let commandBuffer = queue.commandBuffer()
+            let commandEncoder = commandBuffer.computeCommandEncoder()
+            commandEncoder.setComputePipelineState(cps)
+            commandEncoder.setTexture(drawable.texture, atIndex: 0)
+            commandEncoder.setTexture(texture, atIndex: 1)
+            commandEncoder.setBuffer(timerBuffer, offset: 0, atIndex: 0)
+            update()
+            let threadGroupCount = MTLSizeMake(8, 8, 1)
+            let threadGroups = MTLSizeMake(drawable.texture.width / threadGroupCount.width, drawable.texture.height / threadGroupCount.height, 1)
+            commandEncoder.dispatchThreadgroups(threadGroups, threadsPerThreadgroup: threadGroupCount)
+            commandEncoder.endEncoding()
+            commandBuffer.presentDrawable(drawable)
+            commandBuffer.commit()
+        }
+        
+    }
+    
+    func update() {
+        timer += 0.01
+        let bufferPointer = timerBuffer.contents()
+        memcpy(bufferPointer, &timer, sizeof(Float))
+    }
+    
+    func registerShaders() {
+        queue = device!.newCommandQueue()
+        let path = NSBundle.mainBundle().pathForResource("Shaders", ofType: "metal")
+        do {
+            let input = try String(contentsOfFile: path!, encoding: NSUTF8StringEncoding)
+            let library = try device!.newLibraryWithSource(input, options: nil)
+            let kernel = library.newFunctionWithName("compute")!
+            cps = try device!.newComputePipelineStateWithFunction(kernel)
+        } catch let e {
+            Swift.print("\(e)")
+        }
+        timerBuffer = device!.newBufferWithLength(sizeof(Float), options: [])
+    }
+}

ch15/chapter15.playground/contents.xcplayground

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

ch15/chapter15.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:">
+   </FileRef>
+</Workspace>

ch15/chapter15.playground/timeline.xctimeline

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