Possible order-of-operations bug?
Transparent parts need to be assigned a separate material from non-transparent parts, otherwise the whole model is assigned alpha blend, which causes sorting errors in the supposedly-opaque parts.
Thus I must use a Multi/Sub-Object material, which assigns the two materials to different sets of triangles in the same model.
If the transparent material uses the first ID in the Multi/Sub-Object material, then the glass is transparent as expected.
However if the non-transparent material uses the first ID, then the glass is not transparent.
I am using one set of textures for my model, because I want both materials to re-use the same albedo+transparency PNG. The transparent material should use RGB for albedo and Alpha for transparency, while the non-transparent material should use the RGB alone only for albedo.
3ds Max 2018.4