This was an issue I raised a long time ago, and I thought it had been fixed in vbRhinoscript, but I see not (or the fix has been backed out again):
ObjectsByType(8) (surfaces) does not get single-surface extrusion objects
ObjectsByType(16) (polysurfaces) does not get multi-surface extrusion objects
Type 1073741824 extrusion can be added to the list to force this, but it should not be necessary, IMO
Python rhinoscriptsyntax only:
Type 1073741824 extrusion is not included in the Python rhinoscriptsyntax Help for ObjectsByType
rs.IsExtrusion() method does not exist.
Things like rs.IsObjectSolid() fail for extrusion objects -
looks like they simply did not get added in object.py in this case, there may be others as well…
The problem is that Extrusions are not being considered as BReps. This means they are not “transparent”.