diff --git a/Sources/IO/Geometry/IFCImporter/example/controller.html b/Sources/IO/Geometry/IFCImporter/example/controller.html
new file mode 100644
index 00000000000..d77bd53ba33
--- /dev/null
+++ b/Sources/IO/Geometry/IFCImporter/example/controller.html
@@ -0,0 +1,15 @@
+<table>
+  <tr>
+    <td colspan="2">
+      <h3 style="margin: 5px 0;">Options</h3>
+    </td>
+  </tr>
+  <tr>
+    <td>
+      Merge geometries
+    </td>
+    <td>
+      <input type="checkbox" id="mergeGeometries" name="mergeGeometries" value="1" checked>
+    </td>
+  </tr>
+</table>
diff --git a/Sources/IO/Geometry/IFCImporter/example/index.js b/Sources/IO/Geometry/IFCImporter/example/index.js
index 847ad237368..418e12418cf 100644
--- a/Sources/IO/Geometry/IFCImporter/example/index.js
+++ b/Sources/IO/Geometry/IFCImporter/example/index.js
@@ -6,18 +6,33 @@ import '@kitware/vtk.js/Rendering/Profiles/Geometry';
 import vtkFullScreenRenderWindow from '@kitware/vtk.js/Rendering/Misc/FullScreenRenderWindow';
 import vtkResourceLoader from '@kitware/vtk.js/IO/Core/ResourceLoader';
 import vtkIFCImporter from '@kitware/vtk.js/IO/Geometry/IFCImporter';
+import vtkURLExtract from '@kitware/vtk.js/Common/Core/URLExtract';
+
+import controlPanel from './controller.html';
 
 // ----------------------------------------------------------------------------
 // Example code
 // ----------------------------------------------------------------------------
 
+const userParams = vtkURLExtract.extractURLParameters();
+const url =
+  userParams.fileURL ||
+  'https://raw.githubusercontent.com/ThatOpen/engine_web-ifc/refs/heads/main/tests/ifcfiles/public/duplex.ifc';
+const fullScreenRenderer = vtkFullScreenRenderWindow.newInstance();
+fullScreenRenderer.addController(controlPanel);
+
+if (userParams.mergeGeometries === undefined) {
+  userParams.mergeGeometries = true;
+}
+const mergeGeometriesCheckbox = document.querySelector('#mergeGeometries');
+mergeGeometriesCheckbox.checked = Boolean(userParams.mergeGeometries);
+
 const importer = vtkIFCImporter.newInstance({
-  mergeGeometries: true,
+  mergeGeometries: mergeGeometriesCheckbox.checked,
 });
 
 // ----------------------------------------------------------------------------
 function update() {
-  const fullScreenRenderer = vtkFullScreenRenderWindow.newInstance();
   const renderer = fullScreenRenderer.getRenderer();
   const renderWindow = fullScreenRenderer.getRenderWindow();
 
@@ -41,9 +56,9 @@ vtkResourceLoader
     vtkIFCImporter.setIFCAPI(window.WebIFC);
 
     // Trigger data download
-    importer
-      .setUrl(
-        'https://raw.githubusercontent.com/ThatOpen/engine_web-ifc/refs/heads/main/tests/ifcfiles/public/duplex.ifc'
-      )
-      .then(update);
+    importer.setUrl(url).then(update);
   });
+
+mergeGeometriesCheckbox.addEventListener('change', (evt) => {
+  window.location = `?mergeGeometries=${evt.target.checked}`;
+});
diff --git a/Sources/IO/Geometry/IFCImporter/index.js b/Sources/IO/Geometry/IFCImporter/index.js
index b4969c198f0..4aadc02f534 100644
--- a/Sources/IO/Geometry/IFCImporter/index.js
+++ b/Sources/IO/Geometry/IFCImporter/index.js
@@ -14,6 +14,7 @@ import vtkPolyData from 'vtk.js/Sources/Common/DataModel/PolyData';
 import vtkCellArray from 'vtk.js/Sources/Common/Core/CellArray';
 import vtkAppendPolyData from 'vtk.js/Sources/Filters/General/AppendPolyData';
 import vtkMatrixBuilder from 'vtk.js/Sources/Common/Core/MatrixBuilder';
+import { mat3 } from 'gl-matrix';
 
 const { vtkErrorMacro } = macro;
 
@@ -94,11 +95,16 @@ function vtkIFCImporter(publicAPI, model) {
         .buildFromRadian()
         .setMatrix(userMatrix);
 
+      const normalMatrix = vtkMatrixBuilder
+        .buildFromRadian()
+        .multiply3x3(mat3.fromMat4(mat3.create(), userMatrix));
+
       for (let i = 0; i < vertices.length; i += 6) {
         const point = [vertices[i], vertices[i + 1], vertices[i + 2]];
         const normal = [vertices[i + 3], vertices[i + 4], vertices[i + 5]];
 
-        transformMatrix.apply(point).apply(normal);
+        transformMatrix.apply(point);
+        normalMatrix.apply(normal);
 
         pointValues[i / 2] = point[0];
         pointValues[i / 2 + 1] = point[1];
@@ -244,32 +250,32 @@ function vtkIFCImporter(publicAPI, model) {
   publicAPI.importActors = (renderer) => {
     if (model.mergeGeometries) {
       const opaqueMeshes = meshes.filter((mesh) => mesh.color.w === 1);
-      let apd = vtkAppendPolyData.newInstance();
+      const oapd = vtkAppendPolyData.newInstance();
 
       opaqueMeshes.forEach((mesh) => {
         const pd = createColoredPolyDataFromIFCMesh(mesh);
-        apd.addInputData(pd);
+        oapd.addInputData(pd);
       });
 
       let mapper = vtkMapper.newInstance();
       mapper.setColorModeToDirectScalars();
-      mapper.setInputConnection(apd.getOutputPort());
+      mapper.setInputConnection(oapd.getOutputPort());
 
       let actor = vtkActor.newInstance();
       actor.setMapper(mapper);
       renderer.addActor(actor);
 
       const transparentMeshes = meshes.filter((mesh) => mesh.color.w < 1);
-      apd = vtkAppendPolyData.newInstance();
+      const tapd = vtkAppendPolyData.newInstance();
 
       transparentMeshes.forEach((mesh) => {
         const pd = createColoredPolyDataFromIFCMesh(mesh);
-        apd.addInputData(pd);
+        tapd.addInputData(pd);
       });
 
       mapper = vtkMapper.newInstance();
       mapper.setColorModeToDirectScalars();
-      mapper.setInputConnection(apd.getOutputPort());
+      mapper.setInputConnection(tapd.getOutputPort());
 
       actor = vtkActor.newInstance();
       actor.setMapper(mapper);