Hi experts,
there seams to be a Catia function, to split polysurfaces at tangent edges. Is there something similar in Rhino?
Addition: Here are some pictures about this Catia function called “Ableiten”:
Thanks
Michael
Hi Michael,
There is:
http://docs.mcneel.com/rhino/5/help/en-us/commands/dividealongcreases.htm
-Willem
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Hi @Willem,
thank you, but I don’t want to split a single surface at a kink.
I want to extract/(split) a polysurface area from the rest of the polysurface at e.g. tangent edges.
Cheers
Michael
I think @clement posted a python/rhinocommon script awhile back that had a function that detected tangent or curvature continuous joined seam edges (using BrepEdge.IsSmoothManifoldEdge?). Maybe that function could be adapted to split breps along those edges… May be somewhat difficult for arbitrary breps, as to split, one would always need to find one or more fully closed edge loops… --Mitch
You can use DivideAlongCreases command first to divide the polysurface, and then use ExtractSrf command to extract polysurface face.
I think he would like to have this happen automatically…
Hi @Andrew_Nowicki,
I’ve made an example. How to extract the inner part (red) from the outer (green) part not by hand? I want to extract the inner part by selecting edge 1 and its automatically found tangent neighbour edges.
extract_polysurfaces_at_tangent_edges.3dm (500.7 KB)
This is just a simple example. The customer showed me much more complex sheet metals from the car industry.
Thanks,
Michael
@Michael_Meyer In your example edge 1 is a crease, not a tangent edge. The adjacent edge 0.5 mm from edge 1 is also a crease, not a tangent edge.
DivideAlongCreases only works on surfaces; it does not work on polysurfaces.
Hi Mitch, i did not post it. But i see that such a function @Michael_Meyer asks for could potentionally be useful. Just wondering how it should propagate selecting tangent faces from a first face selection and how long ? (eg. connected to first face only or until no more tangent faces are found from the tangent faces etc.)
_
c.
@Michael_Meyer I thought you were talking about surfaces which are tangent but not curvature continuous to each other, not edges which are polycurves with segments tangent but not curvature continuous to each other. Two different situations though both can occur together.
I’m no expert at this stuff, but couldn’t you do something like
-
_SelChainwith Tangency to select the edge curves -
_Dupand_Join -
_Splitthe polysurface with the resulting curve
and then maybe package all that into a macro
Hi @Michael_Meyer - you can try this thing
ExtractTangentFaces_.rhp (39.5 KB)
I use it fairly often for exactly this but, fyi, I had a report of a crash recently as well - it has not crashed for me…
@Michael_Meyer - for what it is worth in the meantime, till Chuck does the thing right, the plug-in used on your little test file:
-Pascal
2 Likes
Hi @qythium,
yes, a script should work.
But why not to integrate more useful commands to enrich Rhino for all?
Thanks
Michael
Hi @pascal,
cool, thank you.
But nethertheless, this seams to be interesting for more users (from Catia). So perhaps a command would be an enrichment.
Cheers
Michael
I agree - it is quite handy and should probably be done right and in Rhino.
-Pascal
I think I can whip off a quick test command. If so, it will be in the 6.5 release candidate. For a start, I will take a polysurface and break it up into clumps of surfaces connected by tangent edges.
1 Like
Hi Chuck,
great, when it’s ready I will send it to my customer, that he can do some tests with his sheet metals. Perhaps he can say more about this Catia stuff and his wishes. I am just the dense messenger, don’t shoot me. 
Cheers
Michael
It would be nice also to have a command like “ExtractTrim” (or maybe ExtractEdge) for polysurfaces, I find myself often using ExtractWireframe and deleting all but a few edges.