From 3bb25af63ab642f1adfecfd840689c7049dcfcf4 Mon Sep 17 00:00:00 2001
From: Marius Horga <marius@MBP.local>
Date: Sun, 1 Oct 2017 15:25:48 -0500
Subject: [PATCH] added particles

---
 README.md                                     |   1 +
 particles/particle.playground/Contents.swift  |   9 +++
 .../Resources/Shaders.metal                   |  30 +++++++++
 .../Sources/MetalView.swift                   |  57 ++++++++++++++++++
 .../particle.playground/contents.xcplayground |   4 ++
 .../contents.xcworkspacedata                  |   7 +++
 .../UserInterfaceState.xcuserstate            | Bin 0 -> 13567 bytes
 .../particle.playground/timeline.xctimeline   |   6 ++
 8 files changed, 114 insertions(+)
 create mode 100644 particles/particle.playground/Contents.swift
 create mode 100644 particles/particle.playground/Resources/Shaders.metal
 create mode 100644 particles/particle.playground/Sources/MetalView.swift
 create mode 100644 particles/particle.playground/contents.xcplayground
 create mode 100644 particles/particle.playground/playground.xcworkspace/contents.xcworkspacedata
 create mode 100644 particles/particle.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate
 create mode 100644 particles/particle.playground/timeline.xctimeline

diff --git a/README.md b/README.md
index 388529c..5241289 100644
--- a/README.md
+++ b/README.md
@@ -29,3 +29,4 @@ Repository to accompany the following blog posts:
 - [Introducing Metal 2](http://metalkit.org/2017/06/30/introducing-metal-2.html)
 - [Using ARKit with Metal](http://metalkit.org/2017/07/29/using-arkit-with-metal.html)
 - [Using ARKit with Metal part 2](http://metalkit.org/2017/08/31/using-arkit-with-metal-part-2.html)
+- [Working with Particles in Metal](http://metalkit.org/2017/09/30/working-with-particles-in-metal.html)
diff --git a/particles/particle.playground/Contents.swift b/particles/particle.playground/Contents.swift
new file mode 100644
index 0000000..694d377
--- /dev/null
+++ b/particles/particle.playground/Contents.swift
@@ -0,0 +1,9 @@
+
+import MetalKit
+import PlaygroundSupport
+
+let frame = NSRect(x: 0, y: 0, width: 400, height: 400)
+let delegate = MetalView()
+let view = MTKView(frame: frame, device: delegate.device)
+view.delegate = delegate
+PlaygroundPage.current.liveView = view
diff --git a/particles/particle.playground/Resources/Shaders.metal b/particles/particle.playground/Resources/Shaders.metal
new file mode 100644
index 0000000..dda48b9
--- /dev/null
+++ b/particles/particle.playground/Resources/Shaders.metal
@@ -0,0 +1,30 @@
+
+#include <metal_stdlib>
+using namespace metal;
+
+struct Particle {
+    float2 center;
+    float radius;
+};
+
+float distanceToParticle(float2 point, Particle p) {
+    return length(point - p.center) - p.radius;
+}
+
+kernel void compute(texture2d<float, access::write> output [[texture(0)]],
+                    constant float &time [[buffer(0)]],
+                    uint2 gid [[thread_position_in_grid]]) {
+    int width = output.get_width();
+    int height = output.get_height();
+    float2 uv = float2(gid) / float2(width, height);
+    float2 center = float2(0.5, time);
+    float radius = 0.05;
+    float stop = 1 - radius;
+    if (time >= stop) { center.y = stop; }
+    else center.y = time;
+    Particle p = Particle{center, radius};
+    float distance = distanceToParticle(uv, p);
+    float4 color = float4(1, 0.7, 0, 1);
+    if (distance > 0) { color = float4(0.2, 0.5, 0.7, 1); }
+    output.write(float4(color), gid);
+}
diff --git a/particles/particle.playground/Sources/MetalView.swift b/particles/particle.playground/Sources/MetalView.swift
new file mode 100644
index 0000000..dde5ba7
--- /dev/null
+++ b/particles/particle.playground/Sources/MetalView.swift
@@ -0,0 +1,57 @@
+
+import MetalKit
+
+public class MetalView: NSObject, MTKViewDelegate {
+    
+    public var device: MTLDevice! = nil
+    var queue: MTLCommandQueue! = nil
+    var cps: MTLComputePipelineState! = nil
+    var timerBuffer: MTLBuffer! = nil
+    var timer: Float = 0
+    
+    override public init() {
+        super.init()
+        device = MTLCreateSystemDefaultDevice()
+        queue = device.makeCommandQueue()
+        registerShaders()
+    }
+    
+    func registerShaders() {
+        guard let path = Bundle.main.path(forResource: "Shaders", ofType: "metal") else { return }
+        do {
+            let input = try String(contentsOfFile: path, encoding: String.Encoding.utf8)
+            let library = try device.makeLibrary(source: input, options: nil)
+            guard let kernel = library.makeFunction(name: "compute") else { return }
+            cps = try device.makeComputePipelineState(function: kernel)
+        } catch let e {
+            Swift.print("\(e)")
+        }
+        timerBuffer = device.makeBuffer(length: MemoryLayout<Float>.size, options: [])
+    }
+    
+    func update() {
+        timer += 0.01
+        let bufferPointer = timerBuffer.contents()
+        memcpy(bufferPointer, &timer, MemoryLayout<Float>.size)
+    }
+    
+    public func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {}
+    
+    public func draw(in view: MTKView) {
+        if let drawable = view.currentDrawable,
+           let commandBuffer = queue.makeCommandBuffer(),
+           let commandEncoder = commandBuffer.makeComputeCommandEncoder()
+        {
+            commandEncoder.setComputePipelineState(cps)
+            commandEncoder.setTexture(drawable.texture, index: 0)
+            commandEncoder.setBuffer(timerBuffer, offset: 0, index: 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.present(drawable)
+            commandBuffer.commit()
+        }
+    }
+}
diff --git a/particles/particle.playground/contents.xcplayground b/particles/particle.playground/contents.xcplayground
new file mode 100644
index 0000000..a93d484
--- /dev/null
+++ b/particles/particle.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>
\ No newline at end of file
diff --git a/particles/particle.playground/playground.xcworkspace/contents.xcworkspacedata b/particles/particle.playground/playground.xcworkspace/contents.xcworkspacedata
new file mode 100644
index 0000000..919434a
--- /dev/null
+++ b/particles/particle.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>
diff --git a/particles/particle.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate b/particles/particle.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate
new file mode 100644
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diff --git a/particles/particle.playground/timeline.xctimeline b/particles/particle.playground/timeline.xctimeline
new file mode 100644
index 0000000..bf468af
--- /dev/null
+++ b/particles/particle.playground/timeline.xctimeline
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>