diff --git a/source/engine/export/exporterbim.js b/source/engine/export/exporterbim.js
index 80e6ffa..e95be2f 100644
--- a/source/engine/export/exporterbim.js
+++ b/source/engine/export/exporterbim.js
@@ -1,6 +1,5 @@
 import { FileFormat } from '../io/fileutils.js';
 import { ColorComponentFromFloat } from '../model/color.js';
-import { ConvertMeshToMeshBuffer } from '../model/meshbuffer.js';
 import { PropertyToString } from '../model/property.js';
 import { ExportedFile, ExporterBase } from './exporterbase.js';
 
@@ -39,42 +38,77 @@ export class ExporterBim extends ExporterBase
 
         let meshId = 0;
         exporterModel.EnumerateTransformedMeshes ((mesh) => {
-            let meshBuffer = ConvertMeshToMeshBuffer (mesh);
-            for (let primitiveIndex = 0; primitiveIndex < meshBuffer.PrimitiveCount (); primitiveIndex++) {
-                let primitive = meshBuffer.GetPrimitive (primitiveIndex);
-                let material = exporterModel.GetMaterial (primitive.material);
-                let bimMesh = {
-                    mesh_id : meshId,
-                    coordinates : primitive.vertices,
-                    indices : primitive.indices
+            let bimMesh = {
+                mesh_id : meshId,
+                coordinates : [],
+                indices : []
+            };
+
+            mesh.EnumerateVertices ((vertex) => {
+                bimMesh.coordinates.push (vertex.x, vertex.y, vertex.z);
+            });
+            mesh.EnumerateTriangleVertexIndices ((v0, v1, v2) => {
+                bimMesh.indices.push (v0, v1, v2);
+            });
+
+            let bimElement = {
+                mesh_id : meshId,
+                type : 'Other',
+                color : {
+                    r : 200,
+                    g : 200,
+                    b : 200,
+                    a : 255
+                },
+                vector : {
+                    x : 0.0,
+                    y : 0.0,
+                    z : 0.0
+                },
+                rotation : {
+                    qx: 0.0,
+                    qy: 0.0,
+                    qz: 0.0,
+                    qw: 1.0
+                },
+                guid : GenerateGuid ()
+            };
+
+            let defaultColor = null;
+            let hasOnlyOneColor = true;
+            let faceColors = [];
+            for (let i = 0; i < mesh.TriangleCount (); i++) {
+                let triangle = mesh.GetTriangle (i);
+                let material = exporterModel.GetMaterial (triangle.mat);
+                let faceColor = {
+                    r : material.color.r,
+                    g : material.color.g,
+                    b : material.color.b,
+                    a : ColorComponentFromFloat (material.opacity),
                 };
-                let bimElement = {
-                    mesh_id : meshId,
-                    type : 'Other',
-                    color : {
-                        r : material.color.r,
-                        g : material.color.g,
-                        b : material.color.b,
-                        a : ColorComponentFromFloat (material.opacity)
-                    },
-                    vector : {
-                        x : 0.0,
-                        y : 0.0,
-                        z : 0.0
-                    },
-                    rotation : {
-                        qx: 0.0,
-                        qy: 0.0,
-                        qz: 0.0,
-                        qw: 1.0
-                    },
-                    guid : GenerateGuid ()
-                };
-                this.ExportProperties (mesh, bimElement);
-                bimContent.meshes.push (bimMesh);
-                bimContent.elements.push (bimElement);
-                meshId += 1;
+                faceColors.push (faceColor.r, faceColor.g, faceColor.b, faceColor.a);
+                if (hasOnlyOneColor) {
+                    if (defaultColor === null) {
+                        defaultColor = faceColor;
+                    } else {
+                        if (defaultColor.r !== faceColor.r || defaultColor.g !== faceColor.g || defaultColor.b !== faceColor.b || defaultColor.a !== faceColor.a) {
+                            hasOnlyOneColor = false;
+                            defaultColor = null;
+                        }
+                    }
+                }
             }
+
+            if (hasOnlyOneColor) {
+                bimElement.color = defaultColor;
+            } else {
+                bimElement.face_colors = faceColors;
+            }
+
+            this.ExportProperties (mesh, bimElement);
+            bimContent.meshes.push (bimMesh);
+            bimContent.elements.push (bimElement);
+            meshId += 1;
         });
 
         let bimFile = new ExportedFile ('model.bim');
diff --git a/source/engine/import/importerbim.js b/source/engine/import/importerbim.js
index 4055d3f..fd16756 100644
--- a/source/engine/import/importerbim.js
+++ b/source/engine/import/importerbim.js
@@ -71,32 +71,29 @@ export class ImporterBim extends ImporterBase
 
     ImportElement (bimElement)
     {
-        let materialIndex = null;
-        if (bimElement.color) {
-            let colorKey =
-                IntegerToHexString (bimElement.color.r) +
-                IntegerToHexString (bimElement.color.g) +
-                IntegerToHexString (bimElement.color.b) +
-                IntegerToHexString (bimElement.color.a);
-            if (this.colorToMaterialIndex.has (colorKey)) {
-                materialIndex = this.colorToMaterialIndex.get (colorKey);
-            } else {
-                let material = new PhongMaterial ();
-                material.name = colorKey;
-                material.color = new Color (bimElement.color.r, bimElement.color.g, bimElement.color.b);
-                if (bimElement.color.a < 255) {
-                    material.opacity = bimElement.color.a / 255.0;
-                    UpdateMaterialTransparency (material);
-                }
-                materialIndex = this.model.AddMaterial (material);
-                this.colorToMaterialIndex.set (colorKey, materialIndex);
-            }
-        }
+        let defaultMaterialIndex = this.GetMaterialIndexForColor (
+            bimElement.color.r,
+            bimElement.color.g,
+            bimElement.color.b,
+            bimElement.color.a
+        );
 
         let rootNode = this.model.GetRootNode ();
 
         let bimMesh = this.meshIdToMesh.get (bimElement.mesh_id);
-        let mesh = this.ImportMesh (bimMesh, materialIndex);
+        let mesh = this.ImportMesh (bimMesh, (triangleIndex) => {
+            if (bimElement.face_colors) {
+                let faceMaterialIndex = this.GetMaterialIndexForColor (
+                    bimElement.face_colors[triangleIndex * 4 + 0],
+                    bimElement.face_colors[triangleIndex * 4 + 1],
+                    bimElement.face_colors[triangleIndex * 4 + 2],
+                    bimElement.face_colors[triangleIndex * 4 + 3]
+                );
+                return faceMaterialIndex;
+            } else {
+                return defaultMaterialIndex;
+            }
+        });
         let meshIndex = this.model.AddMesh (mesh);
 
         let elementNode = new Node ();
@@ -128,7 +125,7 @@ export class ImporterBim extends ImporterBase
         return mesh;
     }
 
-    ImportMesh (bimMesh, materialIndex)
+    ImportMesh (bimMesh, getMaterialIndex)
     {
         let mesh = new Mesh ();
 
@@ -146,9 +143,7 @@ export class ImporterBim extends ImporterBase
                 bimMesh.indices[i + 1],
                 bimMesh.indices[i + 2]
             );
-            if (materialIndex !== null) {
-                triangle.SetMaterial (materialIndex);
-            }
+            triangle.SetMaterial (getMaterialIndex (i / 3));
             mesh.AddTriangle (triangle);
         }
 
@@ -183,4 +178,23 @@ 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/main.js b/source/engine/main.js
index c197c81..4edf9cb 100644
--- a/source/engine/main.js
+++ b/source/engine/main.js
@@ -1,4 +1,4 @@
-import { IsDefined, ValueOrDefault, CopyObjectAttributes } from './core/core.js';
+import { IsDefined, ValueOrDefault, CopyObjectAttributes, IsObjectEmpty } from './core/core.js';
 import { TaskRunner, RunTaskAsync, RunTasks, RunTasksBatch, WaitWhile } from './core/taskrunner.js';
 import { Exporter } from './export/exporter.js';
 import { Exporter3dm } from './export/exporter3dm.js';
@@ -74,6 +74,7 @@ export {
     IsDefined,
     ValueOrDefault,
     CopyObjectAttributes,
+    IsObjectEmpty,
     TaskRunner,
     RunTaskAsync,
     RunTasks,