wonky lofts in 2001+

Dude,

2001+ by this point is pretty antiquated. The best thing you could do to help your customer would be to use a later version of SW. Lofts have improved a lot in the past 5 years.

With complex shapes, it's very difficult to get help from a word description. A picture really might help.

matt

hmm... how can i post a picture here? i don't have a web space to upload them to.

thanks for answering so quickly tho. i don't know if i can get them to invest in the new version.

Yes, I noticed the same type of misbehavior. SW still has a long way to go with its lofts.

There was noticeable improvement in SW 2003 & SW 2004. Still problems, though. I had one simple loft change spontaneously every time the part regenerated. This was in SW 2005.

Try the loft without the guide curves, especially if you have plenty of sections to define the shape. Adding guide curves causes all the problems that you described in your opening description.

It sounds like you mixed up line segments with spline points. The spline is a single segment, and if it isn't it likely ought to be. The line ought to be a single segment.

Clamp out wiggles by breaking up into seperate lofts, using start and end tangency.

Boy, you are using old software. Good luck Ed

ss> Hello,

if i take out the guide curves, the surface is all over the place! i thought i defined my profiles pretty well, and have them even more of them closer together in the area of greater curvature, to try to help it out a bit, but no.

my line was originally a single segment, but after reading about loft problems when the different profiles had a different number of points, i tried adding points to see if it would help. it didn't.

i did end up breaking them up into separate lofts, but it's not letting me do anything about the tangency. that's when i get slight errors or seams when i knit the results together.

so is 2006 the recommended package? is it stable? i know wildfire 1.0 was quickly superceded by 2.0.... but then, that was a big change from

2001

thank you all.

As Matt said, lofts have gotten quite a bit better since 2001+, but tangencies are still sometimes an issue.

This is often not a good idea, because of tangency problems. I will often build half a part and then mirror it, but if I run into problems at the center line, then I go back to making the full part. It's a lot more trouble, but you are more likely to get the shape you want.

This is pretty bizarre behavior. It is not unusual to have the loft not go through the profiles. SW has a hard time figuring out how to follow the guide curve and the profiles, so it elects to deviate from the profiles.

It's hard to remember what 2001+ was capable of. 2004 lets you have tangency relations at the start and end of lofts, tangencies to the side surfaces of a loft, tangencies at the edges of fill surfaces. I think 2006 gives C2 options for tangencies. Make sure you look at all of the options available. You may be missing some possibilities.

Where you put your profiles and how you define them and the guide curves is critical to getting the best output. Download Ed Eaton's tutorials from the DiMonte Group website:

Work your way up from Curvy Stuff 101, through 102, 201 and 301, then Curvy Stuff V Parts 1 and 2, with possibly a side route at some point through Surfacing for Blockheads. You will learn a lot that will be very helpful although the later tutorials may rely on features that you don't have available in 2001+.

ProE is generally conceded to be better at surfacing than SW. That was especially true back in 2001.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

As Ed implied, guide curves are a kind of sometimes necessary evil. If your shape is an easy one for SW to do, you probably won't need any guide curves at all. Guide curves take precedence over the profiles in any conflict between them. The fact that your surface doesn't seem to follow your idea of the expected shape without the guide curves may indicate that the placement of your profiles is not very good.

Putting in more profiles seems like a good idea, but it usually is a very bad idea. Getting the right location for the profile planes is usually the right way to fix problems.

Having the same number of segments in your profiles will help make nicer transitions between the profiles, but won't do anything for your tangency problems.

I don't have 2001+ installed any more, but it seems to me that lofts always allowed you to set start and end tangencies.

The surfacing tools generally get better every release. 2006 is a pretty big improvement over 2004 (we skipped 2005). 2004 was a big improvement over

2001+. 2006 is fairly stable, at least as far as modeling goes. We have problems with graphics (sketches that disappear) and crashing. (But we have crashes in 2004 as well.) People have had problems with drawings and pdf output and others that I have forgotten about, but it's not an utterly hopeless release.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

I hear 07 has some good things in it for surfacing....

If you would like, I could host either an image of the part or the file itself. I'm sure the advice would be much more constructive if you and we were talking about the same things. As a warning, unless anyone here still has SW01+ installed (where's TOP?), you won't be able to read any SW native file anyone in a later version creates, other than a parasolid. Email me.

matt(at)dezignstuff(dot)com.

ss> hmm... how can i post a picture here? i don't have a web space to > upload them to.

All I see are four blanks with a little red x in each. The problem might be on my end, as I have had problems with some other web sites. I've allowed popups.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

woops.

learning a new html editor...

there, that should be better

thanks for the pointer to the tutorials! they were helpful. i moved my profiles to occur at the points of my spline, and that helped the surface a bit, but it's still not perfect. i'm trying breaking it up into smaller chunks, and i'll keep you guys posted on my progress. thanks for your suggestions in the meantime tho!

Thanks for the pictures, Matt.

One thing I didn't say earlier is that you don't need to add straight segments in your profiles to get them to meet tangent at the center. You can add straight construction lines at the ends of your profiles and add relations to make them tangent to the profiles and perpendicular to your center plane.

Listen to Ed's advice. (Something we all should do.) It looks like the top 3 or 4 profiles would make one fairly easy part, the bottom 5 or 6 another, and the center is going to be a struggle no matter how you do it. I suspect you will need to break the center up into a number of easier pieces. Make the big flattish pieces that are perpendicular to your center line, then the rounded piece that ties in easily to the ends, then use lofts or fills to join the big flattish bits to the others. One of Ed's tutorials shows how to build a bottle and that one would be especially good to follow carefully.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"