[all] Add a ball on click; regenerate the field on right click

Metaballs/ViewController.swift

@@ -41,17 +41,36 @@ class ViewController: NSViewController, RendererDelegate {
         super.viewWillAppear()
         renderer.mtkView(metalView, drawableSizeWillChange: metalView.drawableSize)
         for _ in 1...10 {
-            let r = Float(20 + arc4random_uniform(50))
-            field.add(ballWithRadius: r)
+            addBallWithRandomRadius()
         }
     }
 
+    override func mouseDown(with event: NSEvent) {
+        addBallWithRandomRadius()
+    }
+
+    override func rightMouseDown(with event: NSEvent) {
+        field.clear()
+        for _ in 1...10 {
+            addBallWithRandomRadius()
+        }
+    }
+
+    // MARK: - Private
+
     private func newErrorView() -> NSView {
         let view = NSView()
         view.layer?.backgroundColor = NSColor.red.cgColor
         return view
     }
 
+    private func addBallWithRandomRadius() {
+        let base = UInt32(view.bounds.width * 0.05)
+        let variance = UInt32(base * 2)
+        let r = Float(base + arc4random_uniform(variance))
+        field.add(ballWithRadius: r)
+    }
+
     // MARK: - RendererDelegate
 
     var renderSize: CGSize {

MetaballsKit/Metaballs.swift

@@ -110,6 +110,10 @@ public class Field {
         populateBallBuffer()
     }
 
+    public func clear() {
+        balls.removeAll(keepingCapacity: true)
+    }
+
     // MARK: - Metal Configuration
 
     private var device: MTLDevice?