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..35a4e6d3e8c 100644
--- a/Sources/IO/Geometry/IFCImporter/example/index.js
+++ b/Sources/IO/Geometry/IFCImporter/example/index.js
@@ -6,18 +6,30 @@ 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 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();
 
@@ -40,10 +52,20 @@ vtkResourceLoader
     // Pass WebIFC api to vtkIFCImporter
     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);
+    if (userParams.fileURL) {
+      // Trigger data download
+      importer.setUrl(userParams.fileURL).then(update);
+    } else {
+      importer
+        .setUrl(
+          'https://raw.githubusercontent.com/ThatOpen/engine_web-ifc/refs/heads/main/tests/ifcfiles/public/duplex.ifc'
+        )
+        .then(update);
+    }
   });
+
+document.querySelectorAll("input[name='mergeGeometries']").forEach((input) => {
+  input.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..3413753e824 100644
--- a/Sources/IO/Geometry/IFCImporter/index.js
+++ b/Sources/IO/Geometry/IFCImporter/index.js
@@ -11,6 +11,7 @@ import vtkActor from 'vtk.js/Sources/Rendering/Core/Actor';
 import vtkMapper from 'vtk.js/Sources/Rendering/Core/Mapper';
 import vtkDataArray from 'vtk.js/Sources/Common/Core/DataArray';
 import vtkPolyData from 'vtk.js/Sources/Common/DataModel/PolyData';
+import vtkPolyDataNormals from 'vtk.js/Sources/Filters/Core/PolyDataNormals';
 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';
@@ -244,32 +245,40 @@ 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);
       });
 
+      const opdn = vtkPolyDataNormals.newInstance();
+      opdn.setInputConnection(oapd.getOutputPort());
+      opdn.setComputePointNormals(true);
+
       let mapper = vtkMapper.newInstance();
       mapper.setColorModeToDirectScalars();
-      mapper.setInputConnection(apd.getOutputPort());
+      mapper.setInputConnection(opdn.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);
       });
 
+      const tpdn = vtkPolyDataNormals.newInstance();
+      tpdn.setInputConnection(tapd.getOutputPort());
+      tpdn.setComputePointNormals(true);
+
       mapper = vtkMapper.newInstance();
       mapper.setColorModeToDirectScalars();
-      mapper.setInputConnection(apd.getOutputPort());
+      mapper.setInputConnection(tpdn.getOutputPort());
 
       actor = vtkActor.newInstance();
       actor.setMapper(mapper);