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From: Michael Gibson
Hi Alex, it's not actually AOK in Rhino, it only appears that way at first glance.
Rhino has a bug in its handling of 2 rail sweeps with sharp points in the rails. Basically it does not attempt to do anything at all to reposition the profile curve at the kink spot. This makes for a kind of bias in the generated surfaces, only the surface along the first piece from the profile is generated as it should be, all the other pieces afterwards will be incorrect.
In your case the bias is not too pronounced so it looks ok. I've attached an example file where you can more clearly see the problem in Rhino's 2 rail sweep mechanism.
It's not actually failing in MoI, it's generating a correct result. A 2 rail sweep along non-coplanar path curves is not guaranteed to generate surfaces that touch each other. In one rail sweep that also happens but surfaces are extended and trimmed against each other to make the mitered corners. At some point in the future I would like to also do a similar kind of extend + trim mitering for 2 rail sweep and blend as well, it's kind of more difficult case though which is why it doesn't do it currently.
Probably the quickest way to make something like this is to close off the ends and use the Construct > Network command in MoI, like in the 2nd attached file. That won't work in Rhino because Rhino's NetworkSrf command also has buggy handling of curves with sharp corners in it. It's different than the sweep problem though, in Rhino's NetworkSrf it ignores the corners and tries to process it through its fitter as if it was a smooth curve, that results in strange lumpy shaping at what is supposed to be a sharp corner point.
- Michael
Attachments:
2 rail sweep_2.3dm
alex_network.3dm
From: AlexPolo
Hi Michael,
thanks for speedy reply and insight into problem great tip with NETWORK surf didnt know a network surf made from polylines created a quad based mesh really handy.
Best regards
Alex.
From: Phiro
Perhaps the easiest way is to unsharp the lines by adding points near the sharp zone and delete the sharp point before using sweep function ?
Or use a reconstruct script which make softed curve ?
Attachments:
2 rail sweep-1.3dm
2 rail sweep_2-1.3dm
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