From d3190dd7e7e9b3591d089aec996e68be1f9ea695 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Tue, 9 Oct 2018 11:57:35 -0700
Subject: [PATCH] Add color rotation matrix to Parameters

---
 MetaballsKit/Math.swift      | 10 ++++++++++
 MetaballsKit/Metaballs.swift |  5 ++---
 MetaballsKit/Shaders.metal   |  1 +
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/MetaballsKit/Math.swift b/MetaballsKit/Math.swift
index ca2e809..0386bea 100644
--- a/MetaballsKit/Math.swift
+++ b/MetaballsKit/Math.swift
@@ -13,6 +13,7 @@ import simd
 public typealias Float2 = packed_float2
 public typealias Float3 = float3
 public typealias Float4 = float4
+public typealias Matrix2x2 = float2x2
 public typealias Matrix3x3 = float3x3
 public typealias Matrix4x4 = float4x4
 
@@ -42,6 +43,15 @@ extension Float4 {
     }
 }
 
+extension Matrix2x2 {
+    static func rotation(theta: Float) -> Matrix2x2 {
+        return self.init(rows: [
+            Float2(cos(theta), -sin(theta)),
+            Float2(sin(theta),  cos(theta)),
+        ])
+    }
+}
+
 extension Matrix4x4 {
     /// Create a 4x4 orthographic projection matrix with the provided 6-tuple.
     /// @see https://en.wikipedia.org/wiki/Orthographic_projection
diff --git a/MetaballsKit/Metaballs.swift b/MetaballsKit/Metaballs.swift
index b3ee598..a46e2a2 100644
--- a/MetaballsKit/Metaballs.swift
+++ b/MetaballsKit/Metaballs.swift
@@ -49,6 +49,8 @@ public struct Parameters {
     public var color2 = Float4()
     public var color3 = Float4()
 
+    public var colorRotation = Matrix2x2(1.0)
+
     public var colorStyle: ColorStyle {
         get {
             return ColorStyle(rawValue: _colorStyle)!
@@ -234,9 +236,6 @@ public class Field {
                 var r = ball.radius
                 ptr = write(value: &r, to: ptr)
                 ptr = ptr.advanced(by: 4)   // Skip 4 bytes to maintain alignment.
-//                if idx == 0 {
-//                    print("Populated ball \(idx): x:\(ball.position.x), y:\(ball.position.y), r:\(r)")
-//                }
                 idx += 1
             }
         }
diff --git a/MetaballsKit/Shaders.metal b/MetaballsKit/Shaders.metal
index 8c09b8b..28b5c47 100644
--- a/MetaballsKit/Shaders.metal
+++ b/MetaballsKit/Shaders.metal
@@ -44,6 +44,7 @@ typedef struct {
     float target;
     float feather;
     float4 colors[4];
+    float2x2 colorRotation;
 } Parameters;
 
 typedef float3 Ball;