diff --git a/source/engine/import/importerbim.js b/source/engine/import/importerbim.js
index fd16756..caa8156 100644
--- a/source/engine/import/importerbim.js
+++ b/source/engine/import/importerbim.js
@@ -3,15 +3,13 @@ import { Coord3D } from '../geometry/coord3d.js';
 import { Direction } from '../geometry/geometry.js';
 import { ArrayBufferToUtf8String } from '../io/bufferutils.js';
 import { Node, NodeType } from '../model/node.js';
-import { PhongMaterial } from '../model/material.js';
-import { Color, IntegerToHexString } from '../model/color.js';
 import { Mesh } from '../model/mesh.js';
 import { Triangle } from '../model/triangle.js';
 import { ImporterBase } from './importerbase.js';
 import { Quaternion } from '../geometry/quaternion.js';
 import { Matrix } from '../geometry/matrix.js';
 import { Transformation } from '../geometry/transformation.js';
-import { UpdateMaterialTransparency } from './importerutils.js';
+import { ColorToMaterialConverter } from './importerutils.js';
 import { Property, PropertyGroup, PropertyType } from '../model/property.js';
 
 export class ImporterBim extends ImporterBase
@@ -34,13 +32,13 @@ export class ImporterBim extends ImporterBase
     ClearContent ()
     {
         this.meshIdToMesh = null;
-        this.colorToMaterialIndex = null;
+        this.colorToMaterial = null;
     }
 
     ResetContent ()
     {
         this.meshIdToMesh = new Map ();
-        this.colorToMaterialIndex = new Map ();
+        this.colorToMaterial = new ColorToMaterialConverter (this.model);
     }
 
     ImportContent (fileContent, onFinish)
@@ -71,7 +69,7 @@ export class ImporterBim extends ImporterBase
 
     ImportElement (bimElement)
     {
-        let defaultMaterialIndex = this.GetMaterialIndexForColor (
+        let defaultMaterialIndex = this.colorToMaterial.GetMaterialIndex (
             bimElement.color.r,
             bimElement.color.g,
             bimElement.color.b,
@@ -83,7 +81,7 @@ export class ImporterBim extends ImporterBase
         let bimMesh = this.meshIdToMesh.get (bimElement.mesh_id);
         let mesh = this.ImportMesh (bimMesh, (triangleIndex) => {
             if (bimElement.face_colors) {
-                let faceMaterialIndex = this.GetMaterialIndexForColor (
+                let faceMaterialIndex = this.colorToMaterial.GetMaterialIndex (
                     bimElement.face_colors[triangleIndex * 4 + 0],
                     bimElement.face_colors[triangleIndex * 4 + 1],
                     bimElement.face_colors[triangleIndex * 4 + 2],
@@ -178,23 +176,4 @@ export class ImporterBim extends ImporterBase
         }
         target.AddPropertyGroup (propertyGroup);
     }
-
-    GetMaterialIndexForColor (r, g, b, a)
-    {
-        let colorKey = IntegerToHexString (r) + IntegerToHexString (g) + IntegerToHexString (b) + IntegerToHexString (a);
-        if (this.colorToMaterialIndex.has (colorKey)) {
-            return this.colorToMaterialIndex.get (colorKey);
-        } else {
-            let material = new PhongMaterial ();
-            material.name = colorKey;
-            material.color = new Color (r, g, b);
-            if (a < 255) {
-                material.opacity = a / 255.0;
-                UpdateMaterialTransparency (material);
-            }
-            let materialIndex = this.model.AddMaterial (material);
-            this.colorToMaterialIndex.set (colorKey, materialIndex);
-            return materialIndex;
-        }
-    }
 }
diff --git a/source/engine/import/importerstp.js b/source/engine/import/importerstp.js
index d199abd..e8f55fb 100644
--- a/source/engine/import/importerstp.js
+++ b/source/engine/import/importerstp.js
@@ -1,8 +1,7 @@
 import { Direction } from '../geometry/geometry.js';
 import { GetExternalLibPath } from '../io/externallibs.js';
 import { Node } from '../model/node.js';
-import { ColorFromFloatComponents, ColorToHexString } from '../model/color.js';
-import { PhongMaterial } from '../model/material.js';
+import { ColorFromFloatComponents } from '../model/color.js';
 import { ConvertThreeGeometryToMesh } from '../threejs/threeutils.js';
 import { ImporterBase } from './importerbase.js';
 import { ColorToMaterialConverter } from './importerutils.js';
@@ -63,12 +62,7 @@ export class ImporterStp extends ImporterBase
         if (!stepContent.success) {
             return;
         }
-        let colorToMaterial = new ColorToMaterialConverter ((color) => {
-            let material = new PhongMaterial ();
-            material.name = ColorToHexString (color).toUpperCase ();
-            material.color = color;
-            return this.model.AddMaterial (material);
-        });
+        let colorToMaterial = new ColorToMaterialConverter (this.model);
         let rootNode = this.model.GetRootNode ();
         this.ImportNode (stepContent, stepContent.root, rootNode, colorToMaterial);
         onFinish ();
@@ -95,7 +89,7 @@ export class ImporterStp extends ImporterBase
         let materialIndex = null;
         if (occtMesh.color) {
             let color = ColorFromFloatComponents (occtMesh.color[0], occtMesh.color[1], occtMesh.color[2]);
-            materialIndex = colorToMaterial.GetMaterialIndex (color);
+            materialIndex = colorToMaterial.GetMaterialIndex (color.r, color.g, color.b, null);
         }
         let mesh = ConvertThreeGeometryToMesh (occtMesh, materialIndex);
         if (occtMesh.name) {
@@ -104,7 +98,7 @@ export class ImporterStp extends ImporterBase
         if (occtMesh.face_colors) {
             for (let faceColorGroup of occtMesh.face_colors) {
                 let faceColor = ColorFromFloatComponents (faceColorGroup.color[0], faceColorGroup.color[1], faceColorGroup.color[2]);
-                let faceMaterialIndex = colorToMaterial.GetMaterialIndex (faceColor);
+                let faceMaterialIndex = colorToMaterial.GetMaterialIndex (faceColor.r, faceColor.g, faceColor.b, null);
                 for (let i = faceColorGroup.first; i <= faceColorGroup.last; i++) {
                     let triangle = mesh.GetTriangle (i);
                     triangle.SetMaterial (faceMaterialIndex);
diff --git a/source/engine/import/importerutils.js b/source/engine/import/importerutils.js
index 8a81c12..3ce56df 100644
--- a/source/engine/import/importerutils.js
+++ b/source/engine/import/importerutils.js
@@ -1,5 +1,6 @@
 import { IsLower } from '../geometry/geometry.js';
-import { ColorToHexString } from '../model/color.js';
+import { PhongMaterial } from '../model/material.js';
+import { Color, IntegerToHexString } from '../model/color.js';
 
 export function NameFromLine (line, startIndex, commentChar)
 {
@@ -66,21 +67,36 @@ export function UpdateMaterialTransparency (material)
 
 export class ColorToMaterialConverter
 {
-	constructor (createMaterialFunc)
+	constructor (model)
 	{
-		this.createMaterialFunc = createMaterialFunc;
+		this.model = model;
 		this.colorToMaterialIndex = new Map ();
 	}
 
-	GetMaterialIndex (color)
+	GetMaterialIndex (r, g, b, a)
 	{
-		let colorKey = ColorToHexString (color);
+		let colorKey =
+			IntegerToHexString (r) +
+			IntegerToHexString (g) +
+			IntegerToHexString (b);
+		let hasAlpha = (a !== undefined && a !== null);
+		if (hasAlpha) {
+			colorKey += IntegerToHexString (a);
+		}
+
 		if (this.colorToMaterialIndex.has (colorKey)) {
 			return this.colorToMaterialIndex.get (colorKey);
 		} else {
-			let materialIndex = this.createMaterialFunc (color);
-			this.colorToMaterialIndex.set (colorKey, materialIndex);
-			return materialIndex;
+            let material = new PhongMaterial ();
+            material.name = colorKey.toUpperCase ();
+            material.color = new Color (r, g, b);
+            if (hasAlpha && a < 255) {
+                material.opacity = a / 255.0;
+                UpdateMaterialTransparency (material);
+            }
+            let materialIndex = this.model.AddMaterial (material);
+            this.colorToMaterialIndex.set (colorKey, materialIndex);
+            return materialIndex;
 		}
 	}
 }