Autodesk Viewer doesn’t natively load IFC files as a “decorative-only” mesh without processing the data. To achieve what you want, you’ll need to first convert the IFC into a supported lightweight 3D format (like SVF or OBJ) using the Model Derivative API or another converter. Once converted, you can load it in the viewer using viewer.loadExtension('Autodesk.Viewing.SceneBuilder') and add it as a custom geometry layer or overlay scene. By setting it to a separate overlay scene and disabling selection on those fragments (via isSelectable: false in the geometry definition), you can make it purely visual with no interaction — similar to an image overlay, but in 3D space.