struggling with loft command

Replies to This Discussion

Permalink Reply by Hannes Löschke on April 3, 2013 at 1:46pm

GH more or les routes the curves trough to Rhinos loft command. Apart from some checks and the seam adjustment, if you specify it, the GH component shouldn't take much longer than Rhino.

Could you post the curves that give you the problem?

Permalink Reply by KrispyKrem on April 3, 2013 at 4:07pm

the results are also very different from rhino ... i dont know why, i have recently installed rhino5 ... everything else runs fine ...

Attachments:

• share.3dm, 144 KB
• share.gh, 3 KB

Permalink Reply by KrispyKrem on April 3, 2013 at 4:16pm

and when i loft the bottom and the top one , it becomes a brep, and not a surface, so I cannot use the result after ...

Permalink Reply by Hannes Löschke on April 3, 2013 at 5:10pm

Several things:

a) Read about and understand Tolerances

It's not the loft but meshing it for display, that takes forever. You have a ~10m high structure, that is modeled in Milimeters with three digit precision. If you want to mesh that with appropriate visual precision.. well, do the math. If you model something several meters large, stick to meters and use a 0.001 tolerance if you need mm details. Rhino viewport loft doesn't need to mesh right away, that's why it's faster.

b) never model far from origin. Display quality and speed deteriorates with distance to {0,0,0}

c) your curves don't flow in the same direction. Check with "_Dir" in Rhino and adjust as neccessary. Rhino command loft will adjust that. GH's curve alignment in loft can be "tricky"... ;)

d) move the seams of all curves so they match up. Again, the Rhino command does that for you, Gh's loft doesn't.

If seams and curve direction match, you'll get the same result as in Rhino.

On a side note: when lofting between two curves where at least one has kinks (your top one), Loft will decide to split the result at the corners and form the loft from several subcurves. You'll get several subsurfaces that are joined into a BRep. With more smooth curves, the loft will try to solve without splitting at the cost of extra UV isocurves and longer calculation.

Permalink Reply by KrispyKrem on April 3, 2013 at 5:18pm

thx, didnt know about those aspects ..