I have a collada file containing the model for a house (without the sides). When I convert it to glTF most of the solar panels and the back half of the roof is not shown in cesium.
The collada model:

the glTF model (converted from collada):

I have uploaded the collada file to this url so you can download it: https://www.dropbox.com/s/z13blnq3w7libbz/model.zip?dl=0
The resulting glTF file can be found via this url: https://www.dropbox.com/s/0hopzzhb5l9204w/model_gltf.zip?dl=0
Hi,
You might need to put the original jpg/gif textures that the model makes reference to into a relative directory for your application to make use of:
I converted a bunch of sketch-up models from their initial skp files (eg bongo.skp) to dae (plus a directory full of textures called bongo if the skp->dae conversion make it…) and then zipped the dae file eg bongo.dae (and the relevant directory of textures - bongo - in this case) so that I could zip the lot for the conversion process. I then made sure that the original directory of textures were available to the app in the same place where I stored the bongo.gltf file.
Hope you don’t do Bongo over this 