Command to detect upper and lower mould surface

Hi ,

I have a closed solid ( moulded part ) , I am driven by need to detect upper and lower surface given a certain orientation axle.

is there a rhino command to select in one click upper and lower ?

the only command which is returning some kind of result on this respect is “DraftAngleAnalysis” but it is only a visual command and it analyze the angle not the 2 skins.

the other somehow useful command is “silhouette” crv but this command is not just returning the sorrounding crv ( theretical mould parting line ) but also inner curves even if i apply it to a closed solid , thus generating a tangles mass of crv that need a timeconsuming cleanup.

The obvious idea was to used this crv to split the solid thus creating the 2 skins.

does anyone have some suggestions on how to solve efficently this task ? without fixing all curves manually or even worse by selecting surfaces manually

many thanks in advancee

Hello - the DraftAngleAnalysis control (in V7 Beta) has tools to create the curves. There may be more then you need - extras to clean up - but it should make the right ones.


Thanks a lot Pascal ,

this is actually very handy for the task i am trying to accomplish.

I tried to apply it to a random subd shape and the result is useful

the partition curve can be generated within a few clicks


but i still have a problem : the generate curves are not usable for direct splitting of the SUBD .

in order to split by using this curve i need first to to :
1 “pull” the curve to the subd surface by using pull command
2 clean the resulted pulled curves from some of "trash curves " generated by command “pull”
3 only after this i can use the joined / cleaned partition curve to split the subd.

this i already a great and very appreciated improvements but i wonder why partition curves generate by “draftangleanalysis” cannot be directly used to split subd.
Isn’t there a why for you to implement the "pull curve " directly inside the “draftangleanalysis” command ?

many thanks, cheers.

Hello - I would run ToNurbs on a copy of the SubD, get the curves from and split the surface object, and leave the SubD out of it - does that work any better?

BTW, use RibbonOffset to create the parting surfaces.


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HI Pascal and thanks for your suggestion

I tried to convert the subd to nurbs before posting , the splitting problem detected on subd where affecting also derivated Nurbs

I solved the problem by “pulling” the crv in to the nurb polisrf; according to my tests when the curve works on nurbs it’ll work also with subd and viceversa.

Is it maybe connecting with general tolerance , i don’t know. I just think that having the draftanglenanlysis command able to return a ueable crv would smooth out the workflow and add a certain value to this new useful feature. having the need to pull crv to surface and clean the curve before actually being able to use it for following operations is a bit frustrating