Closed Loft
Closed Loft
(OP)
Hi, I am trying to make a closed multisections surface in GSD, that is, with starting and final section being the same and thus having closed guides, and it seems not possible.
Any idea?
Thanks for any help.
Roberto
Any idea?
Thanks for any help.
Roberto





RE: Closed Loft
Can you do an Tools=>Image=>Capture and post here?
If the start and end sections are identical, and co-incidental, it may be a simple surface of revolution solution...and not need guide curves.
RE: Closed Loft
Thanks for your reply Kapitan, I already tried that, what I need is a closed loft, not a revolution, because I have more sections than the one that is initial and final,and my guides are not necessarily circular
I dismissed doing it in two steps because I need G2 in all the surface, and I don“t know how to get that in GSD.
Follow the link to see a screenshot of something similar done in rhinoceros using loft with closed loft option selected
http://paramarch.homedns.org/data/closedloft.jpg
greetings!
RE: Closed Loft
Forever Young
RE: Closed Loft
RE: Closed Loft
This closed surface appears to have no planes of symmetry, it wiil be as good as any section and guide curves, and maybe a spine, that are used. There is requirement for any connections to have G2 continuity - I've usually taken this to mean Curvature Continuty, the following is from the Help Documentation:
This would be a simple task, if only Tangency Continuity (G1) was required, it's a bit more complicated than that to hold a G2 condition. I'm sure it can be done in GSD, maybe using Tangency then Curvature.
Perhaps the way to approach it would be to make the first half using three sections - each with tangency extrusions; then make the second half using start and end sections of the first half - and it's Tangency & Curvature, not the extrusions. Not forgetting the middle section - probably free of any tangency.
It may well be best to not use any guides, but a spine instead. Sometimes too many inputs don't give the best result, if guides are used then it could be important where they intersect the section curves.
An interesting problem Roberto, what are you starting with - just 4 sections? how were the guides constructed?
This shape reminds me of some mathematical surfaces that are defined by a parametric equation, an interesting exercise using VBA macros in Excel, and creating a Loft from an external file...
RE: Closed Loft
As kapitan says, it seems difficult to add G2 to both half lofts, I have tried the aux. extrusions and tangency_then_curvature and seems not to work:
Maybe I could build both surfaces in GSD in a proper way and then impose G2 or even G3 within Freestyle Workbench.
As an option, I moved to imagine&shape and got to something similar deforming a thorus, is not the perfect solution, but since I am checking CATIA/digitalproject capabilities in architecture, it fits me and gives me another point of view to model this dome:
Hope I can get to a good point with this and dont have to go back to rhino.
RE: Closed Loft
I hope that you get a good result for what looking for.
Sparck
RE: Closed Loft
Of course, this diminishing difference approach could go on and on, but if this part is to end up being manufactured, then the reality of machining a mould, or whatever, with a ball-nose cutter and then hand finishing means that one has to think - just how far do you go with all this....
Ideally, the model would be a single surface, but if that is not possible then the next best thing is two halves. Breaking the thing down to four parts is opening up opportunities for (maybe even) more errors.
RE: Closed Loft