Strange lofting problem between 3 curves.

# 1 08-01-2006 , 01:14 PM

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Join Date: Oct 2005

Posts: 37

Hi,

I'm doing a loft between the three curves in the first picture; they are all perfectly straight in z, but have curvature in y. The outer two curves are identical copies, and the center one is similar but with no hump in the middle. (They are the outer and center profiles of a skateboard.)
When I loft between them I get a strange bulging outwards which spills beyond the confines of the curves (See second picture.)

I've tried all the loft options settings to no avail. The problem is reduced if I ensure that all the curves have the same number of CVs, but it's still there a little.

In the end I found a workaround by doing two seperate lofts (curve1 -> curve2, then curve2 -> curve3).

But I'd really like to understand why it's failing between 3 curves???
I find that I use lofting a lot, so if someone could give a technical explanation of when it's likely to fail like this, I might be able to avoid some pitfalls.

Thanks

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# 2 08-01-2006 , 01:15 PM

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(Sorry, pics the wrong way around!)

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# 3 08-01-2006 , 02:27 PM

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Join Date: Apr 2005

Location: Fairfield, CT

Posts: 2,436

First of all, your curves need to have the same number of CV's. If they dont then use the rebuild curve tool.

Next, make sure all of your curves go in the same direction. If they dont then use the reverse curve direction tool.

Uhh... Cant think of anything else.

hope this helps
cYa LaTeR,
MaTt

Live the life you love, love the life you live

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# 4 08-01-2006 , 03:11 PM

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I'm wondering if it's not a "closed" loft surface.
Can't figure it out with this view.

If it's the case, well, prefer closed curves to get full control OR uncheck "closed" loft surfaces option, plus the advises from Matt, you shouldn't have this type of problem.
Then simple face extrudes on the nurbsTransformedToPoly mesh.

Can't think about smthg else either.

Regards, Py.

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# 5 08-01-2006 , 05:21 PM

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Posts: 37

Thanks. I followed all the suggestions (direction, number of CVs, not closed) but the problem still persisted to a lesser extent. But from your advice, I figured it *should* work, so I tried one more thing, rebuilding the curves with Uniform and NumSpans, and it worked OK. (Before, CVs were in quite different positions, but with them more equally spaced, it worked)

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Strange lofting problem between 3 curves.

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