diff --git a/source/engine/geometry/matrix.js b/source/engine/geometry/matrix.js
index a3cde5c..3f374c1 100644
--- a/source/engine/geometry/matrix.js
+++ b/source/engine/geometry/matrix.js
@@ -1,5 +1,6 @@
 import { Quaternion } from './quaternion.js';
 import { Coord3D, VectorLength3D } from './coord3d.js';
+import { Coord4D } from './coord4d.js';
 import { IsEqual, IsNegative } from './geometry.js';
 import { QuaternionFromAxisAngle } from './quaternion.js';
 
@@ -314,12 +315,32 @@ export class Matrix
         return new Matrix (result);
     }
 
+    Transpose ()
+    {
+        let result = [
+            this.matrix[0], this.matrix[4], this.matrix[8], this.matrix[12],
+            this.matrix[1], this.matrix[5], this.matrix[9], this.matrix[13],
+            this.matrix[2], this.matrix[6], this.matrix[10], this.matrix[14],
+            this.matrix[3], this.matrix[7], this.matrix[11], this.matrix[15]
+        ];
+        return new Matrix (result);
+    }
+
+    InvertTranspose ()
+    {
+        let result = this.Invert ();
+        if (result === null) {
+            return null;
+        }
+        return result.Transpose ();
+    }
+
     MultiplyVector (vector)
     {
-        let a00 = vector[0];
-        let a01 = vector[1];
-        let a02 = vector[2];
-        let a03 = vector[3];
+        let a00 = vector.x;
+        let a01 = vector.y;
+        let a02 = vector.z;
+        let a03 = vector.w;
 
         let b00 = this.matrix[0];
         let b01 = this.matrix[1];
@@ -338,12 +359,12 @@ export class Matrix
         let b32 = this.matrix[14];
         let b33 = this.matrix[15];
 
-        let result = [
+        let result = new Coord4D (
             a00 * b00 + a01 * b10 + a02 * b20 + a03 * b30,
             a00 * b01 + a01 * b11 + a02 * b21 + a03 * b31,
             a00 * b02 + a01 * b12 + a02 * b22 + a03 * b32,
             a00 * b03 + a01 * b13 + a02 * b23 + a03 * b33
-        ];
+        );
         return result;
     }
 
diff --git a/source/engine/geometry/transformation.js b/source/engine/geometry/transformation.js
index e2cc94f..86f80e7 100644
--- a/source/engine/geometry/transformation.js
+++ b/source/engine/geometry/transformation.js
@@ -1,4 +1,5 @@
 import { Coord3D } from './coord3d.js';
+import { Coord4D } from './coord4d.js';
 import { Matrix, MatrixIsEqual } from './matrix.js';
 
 export class Transformation
@@ -43,8 +44,9 @@ export class Transformation
 
     TransformCoord3D (coord)
     {
-        let resultVector = this.matrix.MultiplyVector ([coord.x, coord.y, coord.z, 1.0]);
-        let result = new Coord3D (resultVector[0], resultVector[1], resultVector[2]);
+        let coord4D = new Coord4D (coord.x, coord.y, coord.z, 1.0);
+        let resultCoord4D = this.matrix.MultiplyVector (coord4D);
+        let result = new Coord3D (resultCoord4D.x, resultCoord4D.y, resultCoord4D.z);
         return result;
     }
 
diff --git a/source/engine/model/meshutils.js b/source/engine/model/meshutils.js
index 42e880b..372f630 100644
--- a/source/engine/model/meshutils.js
+++ b/source/engine/model/meshutils.js
@@ -1,5 +1,4 @@
-import { Coord3D, CrossVector3D, SubCoord3D } from '../geometry/coord3d.js';
-import { Matrix } from '../geometry/matrix.js';
+import { CrossVector3D, SubCoord3D } from '../geometry/coord3d.js';
 import { Transformation } from '../geometry/transformation.js';
 
 export const MeshType =
@@ -40,15 +39,16 @@ export function TransformMesh (mesh, transformation)
     }
 
     if (mesh.NormalCount () > 0) {
-        let trs = transformation.GetMatrix ().DecomposeTRS ();
-        let normalMatrix = new Matrix ().ComposeTRS (new Coord3D (0.0, 0.0, 0.0), trs.rotation, new Coord3D (1.0, 1.0, 1.0));
-        let normalTransformation = new Transformation (normalMatrix);
-        for (let i = 0; i < mesh.NormalCount (); i++) {
-            let normal = mesh.GetNormal (i);
-            let transformed = normalTransformation.TransformCoord3D (normal);
-            normal.x = transformed.x;
-            normal.y = transformed.y;
-            normal.z = transformed.z;
+        let normalMatrix = transformation.GetMatrix ().InvertTranspose ();
+        if (normalMatrix !== null) {
+            let normalTransformation = new Transformation (normalMatrix);
+            for (let i = 0; i < mesh.NormalCount (); i++) {
+                let normal = mesh.GetNormal (i);
+                let transformed = normalTransformation.TransformCoord3D (normal);
+                normal.x = transformed.x;
+                normal.y = transformed.y;
+                normal.z = transformed.z;
+            }
         }
     }
 }