For some reason selecting, re-extruding (using extrude surface) a poly-surface does not create a lightweight extrusion result.
I can copy the edges of the face and that itself can be made into a lightweight extrusion.
BTW, I was curious has anyone made a utility to globally replace all eligible surfaces to lightweight extrusions? It would seem doable to check for poly-surfaces with 2 parallel similar faces, and recreate the extrusion.
Can you send the model or just the srfs in question to email@example.com please? I’ve also heard some talk about a converter for eligible srfs and polysrfs to extrusions. I’m not sure if it’s possible yet but do know it’s on the radar.
As far as writing a global replacer, it would seem possible to at least do replace axial geometry. That way tolerances should not be such an issue.
Have more than 3 surfaces?
-Are there 2 surfaces that are both flat?
–Irrespective of depth, any 2 surfaces identical?
—Do they overlap axially?
—What’s their depth, distance apart?
—Choose a surface.
—Extrude to depth.
—Copy atributes, yada, yada…
For safety, a copy of result could converted into a poly-surface and then compared to the original poly-surface to make sure that they are actually identical, before the scrap is removed.
I feel that testing might make an iterative/exhaustive test possible. In other words, as long as the converted result is the same as the original, then it’s good–right?
Thanks for the extra info. Would you want to see two extrusion objects on top of each other or one single longer extrusion object? If it’s the latter, you can do this now by turning on the ctrl pts for the EO (extrusion object) and moving the top point up using the Gumball or the Move command. I found a shading bug with this however that I just filed that requires RefreshShade to be run if you are in a shaded mode when doing this. Hopefully that can get tuned up soon.
Another command that might be useful to you is MergeAllFaces if you don’t already know it. Although you will create a polysrf with the method you described (or by using sub-object modeling techniques with the Gumball) you can simplify co-planar faces as a clean up step in many cases with this command.
I think all of this has to do with the input geometry for extrusions needs to be planar, perpendicular to the extrusion direction. Try and create a non-planar curve and extrude it, or a “tilted” curve, that will create a (poly)surface instead of an extrusion.
I suspect that for ExtrudeSrf there should/could be a check if the input surface can be a valid planar and perpendicular profile.