I've been encountering this issue for a while now with my project. I have several (4 mechanical, 2 architectural and 2 structural) linked models, and when I run my simulations there are certain items that don't appear. For example, I have sprinkler lines where the elbows appear, but not the pipes. Or the ventilation units will appear, but not the ducts.
As far as I was able to see, the materials of both visible and invisible objects are listed as "not in use" in materials mapping. I'm truly at a loss as to why these are not appearing. It seems to affect only the generic Revit families. The elements are visible in the ElumTools 3D view but once we launch the render they disappear.
I have the same issue. Assigning a material in the 'object style' tab from the Revit 'Manage' menu worked for some items but not for everything
I am also having this issue specifically with stairways. Assigning/changing the material has not worked.
The issue is most likely missing materials. ElumTools ignores all surfaces without Materials, since it doesn't have a basis to estimate reflectance.
If using Object Styles, with a linked model, make sure the material is assigned to Object Styles in the linked model. Object Styles from the host model do not carry through to linked models. The material actually needs to be applied in the link, and the link reloaded.