[SceneKit] Make SCNMatrix4 column-major in .NET. Fixes #4652.

dotnet/BreakingChanges.md

@@ -74,3 +74,14 @@ These APIs are used to determine whether we're executing in the simulator or
 on a device. Neither apply to a Mac Catalyst app, so they've been removed.
 
 Any code that these APIs will have to be ported to not use these APIs.
+
+## The SceneKit.SCNMatrix4 matrix is transposed in memory.
+
+The managed SCNMatrix4 struct used to be a row-major matrix, while the native
+SCNMatrix4 struct is a column-major matrix. This difference in the memory
+representation meant that matrices would often have to be transposed when
+interacting with the platform.
+
+In .NET, we've changed the managed SCNMatrix4 to be a column-major matrix, to
+match the native version. This means that any transposing that's currently
+done when accessing Apple APIs has to be undone.

src/SceneKit/SCNMatrix4.cs

@@ -26,6 +26,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 
  */
 
+#if !NET
+
 using System;
 using System.Runtime.InteropServices;
 using Foundation;
@@ -170,6 +172,12 @@ public pfloat Determinant
         public SCNVector4 Column0
         {
             get { return new SCNVector4(Row0.X, Row1.X, Row2.X, Row3.X); }
+            set {
+                M11 = value.X;
+                M21 = value.Y;
+                M31 = value.Z;
+                M41 = value.W;
+            }
         }
 
         /// <summary>
@@ -178,6 +186,12 @@ public SCNVector4 Column0
         public SCNVector4 Column1
         {
             get { return new SCNVector4(Row0.Y, Row1.Y, Row2.Y, Row3.Y); }
+            set {
+                M12 = value.X;
+                M22 = value.Y;
+                M32 = value.Z;
+                M42 = value.W;
+            }
         }
 
         /// <summary>
@@ -186,6 +200,12 @@ public SCNVector4 Column1
         public SCNVector4 Column2
         {
             get { return new SCNVector4(Row0.Z, Row1.Z, Row2.Z, Row3.Z); }
+            set {
+                M13 = value.X;
+                M23 = value.Y;
+                M33 = value.Z;
+                M43 = value.W;
+            }
         }
 
         /// <summary>
@@ -194,6 +214,12 @@ public SCNVector4 Column2
         public SCNVector4 Column3
         {
             get { return new SCNVector4(Row0.W, Row1.W, Row2.W, Row3.W); }
+            set {
+                M14 = value.X;
+                M24 = value.Y;
+                M34 = value.Z;
+                M44 = value.W;
+            }
         }
 
         /// <summary>
@@ -307,6 +333,29 @@ public void Transpose()
         #endregion
 
         #region Static
+
+        #region CreateFromColumns
+
+        public static SCNMatrix4 CreateFromColumns (SCNVector4 column0, SCNVector4 column1, SCNVector4 column2, SCNVector4 column3)
+        {
+            var result = new SCNMatrix4 ();
+            result.Column0 = column0;
+            result.Column1 = column1;
+            result.Column2 = column2;
+            result.Column3 = column3;
+            return result;
+        }
+
+        public static void CreateFromColumns (SCNVector4 column0, SCNVector4 column1, SCNVector4 column2, SCNVector4 column3, out SCNMatrix4 result)
+        {
+            result = new SCNMatrix4 ();
+            result.Column0 = column0;
+            result.Column1 = column1;
+            result.Column2 = column2;
+            result.Column3 = column3;
+        }
+
+        #endregion
 
         #region CreateFromAxisAngle
 
@@ -1176,3 +1225,6 @@ public static implicit operator CoreAnimation.CATransform3D (SCNMatrix4 source)
 #endif
     }
 }
+
+#endif // !NET
+