Hello,
I am having touble working with this piece. For some reason the whole side resists all attempst to inset a vertice anywhere:
vertice insert bug.3dm (61.4 KB)
I have tried various ways to recreate the side but for some reason it misbehaves. I am working in R7. Tried it in R8 but that budgs out even more. Thought it might be interesting to have a look and if you find out how did I break it, please feel free to to let me know. I would happily avoid this in the future. 
Thanks
Hi @kral ,
Thanks for the report I’ve filed this as https://mcneel.myjetbrains.com/youtrack/issue/RH-79733.
In the meantime, I found you can fix it by ExtractControlPolygon > ToSubD. I’m not sure how the model got in this state but I’ve asked the developers to see if RepairSubD could be made to fix it.
@kral There is a broken symmetry applied to your SubD, and that is making a lot of SubD commands fail. Run RemoveSymmetry on your SubD, then try again to edit it.
Do you have any more information on how you got the SubD to that state? What steps did you take after you used Reflect on the SubD?
Your example file will allow us to make a couple of things more robust in SubD commands like InsertPoint and RepairSubD, as @BrianJ pointed out. So thank you, for reporting that bug!
Hello,
I believe joining faces with _join and _stitch beaks the symmetry. Didn´t know that I wasn´t supposed to do that, haha. Extruding edge seems to work even when stitching it afterwards.
Hope that helps.
Thanks for that @kral. Do you happen to have a 3dm file of the SubD with the symmetry, before it was made invalid by Join or Stitch?
_Stitch or _Join should not make any objects with invalid symmetries, they should either return an object with a valid symmetry applied (and show both parent and children motifs) or remove the symmetry and return only the parent motif.
In a couple of tests here I could not reproduce a situation where stitching or joining SubD faces would lead to invalid objects or symmetries.
A post was split to a new topic: SubD Bridge: Could work when the ends of the edge sets are touching?
Hello,
symmetry_before.3dm (73.0 KB)
symmetry_after.3dm (73.6 KB)
In R7 both Join and Stitch break the symmetry when joining 2 different objects but the symmetry “gray” doesn´t disappear. In R8 it breaks the same but at least the symmetry “gray” goes away. Joining the objects with Bridge seems to work for me keeping the symmetry and spawning the reflection of the other object to the other side. Funny thing.
Hi @kral, thanks a lot for these files.
In Rhino 7, was able to reproduce the bug that creates a SubD with a Symmetry (i.e. RemoveSymmetry will say Symmetry was removed from 1 SubD), which is broken (i.e. moving a parent vertex does not change the associated child vertex). However that bug does not seem to be present in Rhino 8 so I will not be fixing it in the previous version.
Just for completion, when I say “broken symmetry” I really mean a SubD object that is tagged with a Symmetry, which does not get applied in practice or propagates changes from parent motif to child motif. When the symmetry “gray” goes away (and RemoveSymmetry says One selected SubD had no symmetry set), then the symmetry has already been cleanly removed and is not “broken”.
The “broken symmetry” situation is really bad because it breaks other commands, and is hard to detect and recover from. The “removed symmetry” situation however does not make such bad objects and is sometimes the only good solution for a command’s result.
Stil, banging on your files helped me file a couple of small bugs:
RH-79772 Bridge to symmetrical SubD: Symmetry is removed
RH-79773 Stitch to / from Symmetrical SubD: Symmetry is removed / not previewed
RH-79774 Join disjoint symmetrical SubDs: duplicates objects
RH-79775 Join SubD: SubDSymmetry=Discard is not respected
RH-79776 Join SubD: SubDSymmetry=Keep should try to keep the only available symmetry