diff --git a/GLLara.xcodeproj/project.pbxproj b/GLLara.xcodeproj/project.pbxproj
index 7440100..955e650 100644
--- a/GLLara.xcodeproj/project.pbxproj
+++ b/GLLara.xcodeproj/project.pbxproj
@@ -22,7 +22,7 @@
 		5214471116DE22E1003E260F /* GLLara.help in Resources */ = {isa = PBXBuildFile; fileRef = 5214471016DE22E0003E260F /* GLLara.help */; };
 		52152CEF16B66951001AE54C /* GLLDDSFile.swift in Sources */ = {isa = PBXBuildFile; fileRef = 52152CEE16B66951001AE54C /* GLLDDSFile.swift */; };
 		52232EAE1EFC57D4007FE9AD /* XYAlignedSquare.obj in Resources */ = {isa = PBXBuildFile; fileRef = 52232EAD1EFC57D4007FE9AD /* XYAlignedSquare.obj */; };
-		5224C8EE15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.m in Sources */ = {isa = PBXBuildFile; fileRef = 5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.m */; };
+		5224C8EE15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.swift */; };
 		5224C8F015FABC92002A6C76 /* Accelerate.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 5224C8EF15FABC92002A6C76 /* Accelerate.framework */; };
 		5227833F1C0A6074002E43FD /* GLLNoSelectionView.xib in Resources */ = {isa = PBXBuildFile; fileRef = 522783411C0A6074002E43FD /* GLLNoSelectionView.xib */; };
 		522783421C0A6079002E43FD /* GLLPoseExportViewController.xib in Resources */ = {isa = PBXBuildFile; fileRef = 522783441C0A6079002E43FD /* GLLPoseExportViewController.xib */; };
@@ -411,8 +411,7 @@
 		5214471016DE22E0003E260F /* GLLara.help */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = GLLara.help; sourceTree = "<group>"; };
 		52152CEE16B66951001AE54C /* GLLDDSFile.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GLLDDSFile.swift; sourceTree = "<group>"; };
 		52232EAD1EFC57D4007FE9AD /* XYAlignedSquare.obj */ = {isa = PBXFileReference; lastKnownFileType = text; name = XYAlignedSquare.obj; path = Shaders/XYAlignedSquare.obj; sourceTree = "<group>"; };
-		5224C8EC15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = GLLAngleRangeValueTransformer.h; sourceTree = "<group>"; };
-		5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GLLAngleRangeValueTransformer.m; sourceTree = "<group>"; };
+		5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GLLAngleRangeValueTransformer.swift; sourceTree = "<group>"; };
 		5224C8EF15FABC92002A6C76 /* Accelerate.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Accelerate.framework; path = System/Library/Frameworks/Accelerate.framework; sourceTree = SDKROOT; };
 		522783661C0A60E6002E43FD /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/MainMenu.xib; sourceTree = "<group>"; };
 		522783671C0A60E6002E43FD /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/GLLRenderWindowController.xib; sourceTree = "<group>"; };
@@ -1443,8 +1442,7 @@
 				52D6A09515F8B0F7002A0BB4 /* GLLMeshViewController.m */,
 				522783591C0A609B002E43FD /* GLLMeshView.xib */,
 				522783561C0A6096002E43FD /* GLLLightView.xib */,
-				5224C8EC15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.h */,
-				5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.m */,
+				5224C8ED15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.swift */,
 				52C9F60B15FF1752003272E1 /* GLLItemViewController.h */,
 				52C9F60C15FF1752003272E1 /* GLLItemViewController.m */,
 				522783531C0A6091002E43FD /* GLLItemView.xib */,
@@ -1879,7 +1877,7 @@
 				52D6A09715F8B0F7002A0BB4 /* GLLMeshViewController.m in Sources */,
 				52CDFEA82874161400BC4298 /* GLLVertexAttrib.swift in Sources */,
 				52BB217D15F972AB00937450 /* GLLSceneModel.xcdatamodeld in Sources */,
-				5224C8EE15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.m in Sources */,
+				5224C8EE15FA8FB0002A6C76 /* GLLAngleRangeValueTransformer.swift in Sources */,
 				5274448228031C0C00E5A3FD /* GLLModelDrawData.swift in Sources */,
 				52BB21C815FC732A00937450 /* GLLRenderParameter.m in Sources */,
 				521102EF2899C430001BE4BC /* GLLItemBoneExtensions.swift in Sources */,
diff --git a/GLLara/GLLAngleRangeValueTransformer.h b/GLLara/GLLAngleRangeValueTransformer.h
deleted file mode 100644
index f6318dc..0000000
--- a/GLLara/GLLAngleRangeValueTransformer.h
+++ /dev/null
@@ -1,17 +0,0 @@
-//
-//  GLLAngleRangeValueTransformer.h
-//  GLLara
-//
-//  Created by Torsten Kammer on 07.09.12.
-//  Copyright (c) 2012 Torsten Kammer. All rights reserved.
-//
-
-#import <Foundation/Foundation.h>
-
-/*
- * Exactly what it says on the tin.
- * The idea is that rotations are stored from 0…2pi here, but for sliders, you really want -pi…+pi instead. This transformer solves that issue.
- */
-@interface GLLAngleRangeValueTransformer : NSValueTransformer
-
-@end
diff --git a/GLLara/GLLAngleRangeValueTransformer.m b/GLLara/GLLAngleRangeValueTransformer.m
deleted file mode 100644
index 51a96d0..0000000
--- a/GLLara/GLLAngleRangeValueTransformer.m
+++ /dev/null
@@ -1,39 +0,0 @@
-//
-//  GLLAngleRangeValueTransformer.m
-//  GLLara
-//
-//  Created by Torsten Kammer on 07.09.12.
-//  Copyright (c) 2012 Torsten Kammer. All rights reserved.
-//
-
-#import "GLLAngleRangeValueTransformer.h"
-
-@implementation GLLAngleRangeValueTransformer
-
-+ (BOOL)allowsReverseTransformation
-{
-    return YES;
-}
-
-+ (Class)transformedValueClass
-{
-    return [NSNumber class];
-}
-
-- (id)reverseTransformedValue:(id)value
-{
-    if ([value doubleValue] < 0.0)
-        return @([value doubleValue] + M_PI*2);
-    else
-        return value;
-}
-
-- (id)transformedValue:(id)value
-{
-    if ([value doubleValue] > M_PI)
-        return @([value doubleValue] - M_PI*2);
-    else
-        return value;
-}
-
-@end
diff --git a/GLLara/GLLAngleRangeValueTransformer.swift b/GLLara/GLLAngleRangeValueTransformer.swift
new file mode 100644
index 0000000..517faa3
--- /dev/null
+++ b/GLLara/GLLAngleRangeValueTransformer.swift
@@ -0,0 +1,38 @@
+//
+//  GLLAngleRangeValueTransformer.m
+//  GLLara
+//
+//  Created by Torsten Kammer on 07.09.12.
+//  Copyright (c) 2012 Torsten Kammer. All rights reserved.
+//
+import Foundation
+
+/*
+ * Exactly what it says on the tin.
+ * The idea is that rotations are stored from 0…2pi here, but for sliders, you really want -pi…+pi instead. This transformer solves that issue.
+ */
+@objc class GLLAngleRangeValueTransformer: ValueTransformer {
+    @objc override class func allowsReverseTransformation() -> Bool {
+        return true
+    }
+    @objc override class func transformedValueClass() -> AnyClass {
+        return NSNumber.self
+    }
+    
+    override func transformedValue(_ value: Any?) -> Any? {
+        let double = (value as! NSNumber).doubleValue
+        if double > Double.pi {
+            return double - Double.pi * 2
+        } else {
+            return double
+        }
+    }
+    
+    override func reverseTransformedValue(_ value: Any?) -> Any? {
+        let double = (value as! NSNumber).doubleValue
+        if double < 0.0 {
+            return double + Double.pi * 2
+        } else {
+            return double
+        }    }
+}
diff --git a/GLLara/GLLDocument.m b/GLLara/GLLDocument.m
index 1b6b23a..7297436 100644
--- a/GLLara/GLLDocument.m
+++ b/GLLara/GLLDocument.m
@@ -10,7 +10,6 @@
 
 #import <UniformTypeIdentifiers/UniformTypeIdentifiers.h>
 
-#import "GLLAngleRangeValueTransformer.h"
 #import "GLLCamera.h"
 #import "GLLDocumentWindowController.h"
 #import "GLLItem.h"