Hi,
I experienced a very similar problem and found a solution that might help.
When creating transparent panels (like doors or windows), FlexSim only renders the transparency correctly if the transparent geometry is separated in the shape tree — that is, if it is not part of the same mesh or object hierarchy as the components behind it.
⚠️ Key point: This separation must be done in the 3D design software, not inside FlexSim.
In my case, I had one part of a cabinet (a transparent door) that was added later in CATIA. When I exported the entire model as a single STEP or FBX, the transparency did not render correctly in FlexSim — the whole cabinet looked invisible.
But when I exported the transparent door separately as an IGS file, and then reintegrated it into the same CAD assembly, FlexSim interpreted it as a separate shape node in the tree, and transparency worked perfectly — I could see the internal parts behind the glass.
So, even if you're working with one model, ensure that the transparent parts are logically separated (separate export structure), so that FlexSim's renderer processes them in the correct order.
n this image, both panels are transparent and the interior of the cabinet is clearly visible.
This is because both panels are defined independently from the main object in the 3D model hierarchy.
In the second example, the vertical panel appears transparent because its node was manually reordered in FlexSim.
However, it does not show transparency toward the interior of the cabinet, since it is still structurally part of the same shape as the rest of the object.
The difference can be seen in the blue vertical panel.
I hope this sheds light on your issue!
