GDL TUBE and cross-section status codes

[matjashka]

Hi All,

I'm struggling with application of si status codes in the TUBE object, trying to hide lateral edges or surfaces.
The TUBE status consists of two parts: the main directive in first line is j1 to j8 (1+2+16+32+64+128) and affects the whole tube in a very generic manner: there are 2 for each base and 2 for lateral edges.

Then the manual says that the cross-section polyline can be controlled by si status codes for individual edge and surface visibility and the "a_codes" which introduce curves, holes, etc.

In my limited experience, ONLY the a_codes work in a given TUBE, the si codes don't seem to affect anything at all. I've tried various combinations. What am I doing wrong? If TUBE does not support si codes in the extruded shape, why is that part of the spec?
(I'm still using version 16).

Thanks!