Allow a slider to set the colorRotation in radians

MetaballsKit/Math.swift

@@ -43,13 +43,21 @@ extension Float4 {
     }
 }
 
-extension Matrix2x2 {
+extension Matrix3x3 {
-    static func rotation(theta: Float) -> Matrix2x2 {
+    static func rotation(angle theta: Float) -> Matrix3x3 {
         return self.init(rows: [
-            Float2(cos(theta), -sin(theta)),
+            Float3(cos(theta), -sin(theta), 0.0),
-            Float2(sin(theta),  cos(theta)),
+            Float3(sin(theta),  cos(theta), 0.0),
+            Float3(0, 0, 1),
         ])
     }
+
+    static func translation(dx: Float, dy: Float) -> Matrix3x3 {
+        var mat = self.init(1.0)
+        mat.columns.2.x = dx
+        mat.columns.2.y = dy
+        return mat
+    }
 }
 
 extension Matrix4x4 {

MetaballsKit/Metaballs.swift

@@ -49,7 +49,7 @@ public struct Parameters {
     public var color2 = Float4()
     public var color3 = Float4()
 
-    public var colorRotation = Matrix2x2(1.0)
+    public var colorTransform = Matrix3x3(1.0)
 
     public var colorStyle: ColorStyle {
         get {
@@ -303,6 +303,19 @@ public class Field {
             didChange = true
         }
 
+        if let rotation = userInfo["colorRotation"] as? Float {
+            // Create a transform matrix to handle it
+            let dx = Float(size.x) / 2.0
+            let dy = Float(size.y) / 2.0
+            let translate = Matrix3x3.translation(dx: dx, dy: dy)
+            let rotate = Matrix3x3.rotation(angle: rotation)
+            let invTranslate = Matrix3x3.translation(dx: -dx, dy: -dy)
+            parameters.colorTransform = invTranslate * rotate * translate
+            // Save the value to defaults
+            defaults.colorRotation = rotation
+            didChange = true
+        }
+
         if didChange {
             populateParametersBuffer()
         }

MetaballsKit/Preferences.swift

@@ -92,6 +92,21 @@ extension UserDefaults {
         }
     }
 
+    public var colorRotation: Float {
+        get {
+            if let obj = object(forKey: "colorRotation") as? NSNumber {
+                return obj.floatValue
+            } else {
+                let defaultValue: Float = 0.0
+                set(defaultValue, forKey: "colorRotation")
+                return defaultValue
+            }
+        }
+        set {
+            set(newValue, forKey: "colorRotation")
+        }
+    }
+
     func float4(forKey key: String) -> Float4? {
         guard let values = array(forKey: key) as? [Float], values.count >= 4 else {
             return nil

MetaballsKit/PreferencesViewController.swift

@@ -14,6 +14,10 @@ private struct StyleItem {
     let name: String
     let tag: Int
     let colorNames: [String]
+
+    var allowsRotation: Bool {
+        return colorNames.count > 1
+    }
 }
 
 public class PreferencesViewController: NSViewController {
@@ -43,6 +47,14 @@ public class PreferencesViewController: NSViewController {
     private var colorStackView = NSStackView()
     private var colorViews = [ColorView]()
 
+    private lazy var colorRotationSlider: RotationSliderView = {
+        let rotationSlider = RotationSliderView(label: NSLocalizedString("Color θ", comment: "name of color rotation slider"))
+        rotationSlider.slider.target = self
+        rotationSlider.slider.action = #selector(PreferencesViewController.sliderDidUpdate(sender:))
+        rotationSlider.slider.floatValue = self.defaults.colorRotation
+        return rotationSlider
+    }()
+
     private lazy var targetSlider: SliderView = {
         let targetSlider = SliderView(label: NSLocalizedString("Target", comment: "name of the target slider"))
         if #available(OSX 10.12.2, *) {
@@ -135,6 +147,7 @@ public class PreferencesViewController: NSViewController {
             colorStackView.addArrangedSubview(colorView)
             colorViews.append(colorView)
         }
+        colorStackView.addArrangedSubview(colorRotationSlider)
 
         colorStackView.addArrangedSubview(targetSlider)
         colorStackView.addArrangedSubview(featherSlider)
@@ -217,6 +230,9 @@ public class PreferencesViewController: NSViewController {
                 colorView.isHidden = true
             }
         }
+
+        // Hide the color rotation slider if there's only one color
+        colorRotationSlider.isHidden = styleItem.colorNames.count == 1
     }
 
     func postColorNotification() {
@@ -229,6 +245,7 @@ public class PreferencesViewController: NSViewController {
         }
         info["target"] = targetSlider.slider.floatValue
         info["feather"] = featherSlider.slider.floatValue
+        info["colorRotation"] = colorRotationSlider.slider.floatValue
         NotificationCenter.default.post(name: PreferencesDidChange_Color, object: nil, userInfo: info)
     }
 }
@@ -304,3 +321,18 @@ class SliderView: ParameterView {
         fatalError("init(coder:) has not been implemented")
     }
 }
+
+class RotationSliderView: SliderView {
+    override init(label: String) {
+        super.init(label: label)
+
+        let slider = control as! NSSlider
+        slider.minValue = -Double.pi
+        slider.maxValue = Double.pi
+        slider.numberOfTickMarks = 5
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}

MetaballsKit/Shaders.metal

@@ -44,7 +44,7 @@ typedef struct {
     float target;
     float feather;
     float4 colors[4];
-    float2x2 colorRotation;
+    float3x3 colorTransform;
 } Parameters;
 
 typedef float3 Ball;