Hi
Due to installer size limitations, not all grid files are included with initial FME installation, but instead are contained in a separate zip file available from https://fme.safe.com/downloads/.
On Mac, please unzip the file into your Library/FME/2025.0 folder, where 2025.0 represents the version of FME you have installed.
With the extra grids installed, your reprojection should be successful.
But the conversion still doesn't work. Are there any tools that can convert ifc provided by fme to 3dtiles?
Please try using the new Industry Foundation Classes (IFC) reader available in FME 2025.0 and newer. This new reader produces a simpler geometry and attribute structure better suited for conversion into formats like Cesium.
The reprojection in your workspace may not be necessary - the Cesium writer automatically converts from the source coordinate system to the geocentric coordinate system used by 3DTiles. However, the 3DTiles created by FME have relative elevations (to the local ground elevation), so you may want to use an Offsetter to adjust the Z values of the model so that the ground level is set to 0.