From 94c7ad4f584c7cadff57514b22a46ac7419d4b15 Mon Sep 17 00:00:00 2001
From: Robert Rouhani <robert.rouhani@gmail.com>
Date: Sat, 26 Jan 2013 12:57:19 -0500
Subject: [PATCH] Implemented Matrix3(d) constructor that takes upper-left 3x3
 of a Matrix4(d) as discussed in the following issue:
 https://github.com/andykorth/opentk/issues/4

---
 Source/OpenTK/Math/Matrix3.cs  | 11 +++++++++++
 Source/OpenTK/Math/Matrix3d.cs | 13 ++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Source/OpenTK/Math/Matrix3.cs b/Source/OpenTK/Math/Matrix3.cs
index efd0a895..74b34608 100644
--- a/Source/OpenTK/Math/Matrix3.cs
+++ b/Source/OpenTK/Math/Matrix3.cs
@@ -99,6 +99,17 @@ namespace OpenTK
             Row1 = new Vector3(m10, m11, m12);
             Row2 = new Vector3(m20, m21, m22);
         }
+
+        /// <summary>
+        /// Constructs a new instnace.
+        /// </summary>
+        /// <param name="matrix">A Matrix4 to take the upper-left 3x3 from.</param>
+        public Matrix3(Matrix4 matrix)
+        {
+            Row0 = matrix.Row0.Xyz;
+            Row1 = matrix.Row1.Xyz;
+            Row2 = matrix.Row2.Xyz;
+        }
         
         #endregion
         
diff --git a/Source/OpenTK/Math/Matrix3d.cs b/Source/OpenTK/Math/Matrix3d.cs
index 788462cf..d5657ba5 100644
--- a/Source/OpenTK/Math/Matrix3d.cs
+++ b/Source/OpenTK/Math/Matrix3d.cs
@@ -94,7 +94,18 @@ namespace OpenTK
             Row1 = new Vector3d(m10, m11, m12);
             Row2 = new Vector3d(m20, m21, m22);
         }
-        
+
+        /// <summary>
+        /// Constructs a new instance.
+        /// </summary>
+        /// <param name="matrix">A Matrix4d to take the upper-left 3x3 from.</param>
+        public Matrix3d(Matrix4d matrix)
+        {
+            Row0 = matrix.Row0.Xyz;
+            Row1 = matrix.Row1.Xyz;
+            Row2 = matrix.Row2.Xyz;
+        }
+
         #endregion
         
         #region Public Members