Extend Surface w/History - Surfaces Break

In this example, the child surfaces break when the parent is modified using the extend surface tool.

They are fine when transforming the main surface using move, scale, move control points)

Version 7 SR22 (7.22.22255.5001, 2022-09-12)

ext srf breaking.3dm (214.5 KB)

Hi Sach - yep, I see that, thanks - it looks like edge indices are rearranged on extending, my guess is that is fixable.

Edge indices before and after extending -

History depends on edge indices to know where to put things.

RH-70644 ExtendSrf: changes edge indices


Thanks Pascal. I think I’ve noticed this on and off between Rhino versions…

HI @pascal
srf corrupts.3dm (221.5 KB)

I/m noticing this behaviour with split/merge edge and match when there is history on surfaces.

E.g. in the the attached, the magenta srf was created with blend srf w/history on. When I split the edge highlighted in yellow, the srf goes crazy…


srf corrupts.3dm (221.5 KB)

Yeah, that is because it matches to an indexed edge, by closest points - when you split the edge, the added edge is indexed to be the short one on the left, by the look of it, and the entire matched edge is sucked over to the closest point on that edge - which in this case is that corner.
I’ll add this to the pile, but I think it is on there in various forms - I do not know how fixable that is - I lobbied for breaking history in these cases in preference to making something stupid, I may try to revive that campaign.
RH-62959 MatchSrf: Matched surface will be distorted after trimming


Pls count my vote. I can’t count the times I had to undo, and HistoryPurge on items that behaved that way.

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Thanks Pascal.