Import Splines With Tangency

After you've created your curves from the .IBL or .IGS file, do 'Edit>Definition' and, with the Curves box checked, hit Done. You'll get the 'Edit Curves' menu manager with several menu items that could be of use, though none directly allows setting end point tangencies. However, you can select additonal spline points or trim/extend curves or even edit the data file. I don't know, for sure, but one or more of these could give you that kind of control. Adjust is also pretty powerful, if you can figure out how to use it.

David Janes

Obviously it could but it probably assumes the curve described by the points is what is intended. I would. I'm not big on guessing games or typing. If you'll describe goal and technique in at least as many words I'll try to suggest something appropriate for the situation or a more appropriate technique. Chances are imposing a continuity condition will result in unwanted curve oscillation.

One-size-fits-all answers adding to DJ's - Independent Geometry Feature, Edit / Modify CSys Offset Pts, Curve thru Pts / Whole Array.

There are other issues, as well. The first is that it's not at all clear, from the IBL samples I have and have used to construct curves, that these curves are splines and if not, then no end point conditions can be set. To be certain that they were splines, it would be better to export the point data from these curves and use that to import a point array, then create curves as described above. Is that what the Independent Geometry Feature does? Isn't that one of those things from REXX?

David Janes

They are unless the curve definition is two points. Then its a line. That's documented in Help somewhere.

The Independent Geometry feature showed up in WF2 with the addition of Scan-Tools to the FA license? It allows you to copy or move standard model mode feature geometry into the same environment used for Import Feature geometry manipulation.

Okay, well I'll have to try this with some IBL created geometry and see what use can be made of it. Any "user friendliness" built in? Import Feature editing is horrendous! And probably not what the OP is looking for.

David Janes

Personally, I find the Import Feature editing environment satisfactory. It could be more friendly but, and often as not this is the problem, if there's a substitute for working knowledge of surface definition, structure, manipulation; I haven't found it. I've patched up many megabytes of imported model geometry in it. I do most of it manually. Tedious, time consuming, effective to the extent the exported model quality allows. I don't know that there are any shortcuts. I haven't seen an auto healer that didn't suck, I'm talking over and above minimal make-it-solid quality, on anything other than plane and cylinder intersections with simple rounds. Maybe the twenty grand + marvels. Out of my league.

The OP's situation would lead to an interface that's about identical to that seen via Datum Curve / Edit Definition / Tweak, with the addition of a Constraints drop down tab.

Try it, though. My opinions are my own. And though I haven't heard enough to know, still suspect he doesn't want to add a continuity constraint to a curve thru a fit point set. The task wasn't described. For all I know he's tracing through a point set to create an airfoil section or something equally inelegant.

Probably just my lack of experience with it. Like a lot of other things, once you know it, it may seem 'easy'.

I actually have a lot of experience with surface construction and debugging, but find the 'Edit>Definition' of imported features so totally obscure, I probably dodn't try very hard. What are you supposed to do with the one 'Modify' icon you're presented with!?! ....

Maybe, but he was trying to deal with IBL imported curves and there doesn't seem to be much you can do with them, except through the MM interface that's provided with 'Edit>Definition' as I described.

I guess I'm softening in my old age because I've usually prefaced answers to questions like this with more questions, to gain definiton of the problem. So, you're right, we're guessing. I guess wrong a lot and don't like to play that game. Maybe we should make a pact to "nail" the OPs and find out exactly what they want, what their situation is, what they've tried, i.e., get a more complete story, before we go out on a limb with an "educated" guess. After all, the education was from other, 'similar' questions that may not be similar at all. And, as an aid to that definition, I have been pushing, here and with USENET, for making this a binary NG. I'm sure there'd need to be a vote; tell me you hate/love the idea.

David Janes

messagenews: snipped-for-privacy@corp.supernews.com...

Thanks for the discussion. I'm not familar with the Independent Geometry feature, and I'm not sure what you mean by Import Feature. Can you tell me where to go in the menu so I try it out?

I've imported the IBL file as datum curves. Edit Definition allows some manipulation of the curve definition, but as far as I can tell does not allow end conditions to be specified.

My workaround has been to scrap the IBL's and just read in the spline points as Datum Points Offset from CSYS. Create spline through points with appropriate tangency end conditions.

Dave

Could you use the IBL file for the point array definition? If not, where did you get the points?

David Janes

This is probably more than you want to know but here's the entire scope of the project:

1) Started with an existing model with a complex surface built using Style Tool. 2) Saved style curves used to construct the surface as an IGES. 3) In a new model: create datum curves from file, using IGES. 4) Edit Definition (Redefine), Edit File brings up the control points for the IGES curves in IBL format. 5) I then manipulated points in the IBL file (using Excel and some VBA macros) to modify the surface. Several iterations were processed and analyzed using FEA to meet a target mass and stiffness for the feature. 6) This is where I tried to read in the modified IBL files but could not figure out how to set the tangency end conditions. The original IGES file had tangent splines, and when imported in step 4, the spines are tangent. However, if you read the un-manipulated IBL generated in Step 4 the curves are no longer tangent.

7) My work around was just to strip the IBL formatting from the IBL file to create a "point file". Then use the Datum Point offset CSYS feature, copy paste the point data from the point file. Then define curves, through points with specified tangency end constraints.

Here, for some reason, possibly related to NG culture, we don't get enough ramblers, those who tell us way MORE than we need to know. We, despite the astronomical augmentation in capacity and speed, still pretend we're some tightnit, close (and enclosed) little community of scientists working on classified DoD projects, but needing a secure and cheaper-than-Ma-Bell method of communicating conversational information quickly. So, short posts, approximating telegraphic messages (with 'stops' in them) and short cut communication with abbreviations, acronyms and anything else to make it more like the telephonic in immediacy and speed. My way of saying no need to apologize for what I asked for or for giving us the needed level of detail that will help us dig into your problem. In fact, our usual complaint is that we get too many questions on the order of "can i make a solid protrusion in pro/e" to which we must inevitably answer "yes", since the broadest, most vague questions receive the broadest, most contentless answers. OTOH, the more pointed the question, the more precise (and to the point) the answer.

Huh, why? From the start, where are you going with this, what are you trying to accomplish? This is entirely missing in your presentation. Many of the problems we encounter in this forum is misconceptions of how to get where people want to go, and so they try to take bizarre, circuitous routes and wind up at dead ends in the maze.

Again, why? For manipulation of curves/surfaces, you had one of the best tools in the world ~ the Style feature. Don't see where you're going with this but it seems like an extraordinarily roundabout way of getting there. Maybe what is missing is a simple statement of "I am trying to get from HERE to THERE" with enough detail of what 'here' and 'there' are to to form a picture of the transition, the path, the process. So far, this seems extraordinarily convoluted and unlike anything we've used or seen demo'd before. Thus, I suspect you're "off the reservation" and lost, beating the bush, hoping to find a familiar landmark. I can't provide you with one, don't know where you are or where you're going. Spare no words on these relevant subjects.

David Janes

Au contraire. That's exactly what's necessary to formulate relevant suggestions.

The problem you are seeing is due to fact that ... > Edit File brings up the control points > for the IGES curves in IBL format. ... is a misconception. What you be looking at is the knot vector / list or "fit" points; an incomplete curve definition. Thus the loss of tangent direction.

I ~might~ do just as you are ... format pt list, crv thru pts. I doubt, seriously, I'd worry with tangent direction. The curve is good for reference only. If you have Scan-Tools look into Scan Crv creation. I ~believe~ it would be precisely what you want for Deviation Analysis references while you manipulate your existing ISDX Style feature curves to match. Alternatively, you could just use the point set for deviation references but that's not as nifty a deal if I understand correctly.

If, for some reason, I actually wanted to reconstruct surfaces using the import curves explicitly I believe I'd create the curves without constraints, look at a curvature graph, apply constraints, look at curve graph again.

Is this a class project? How "complex" are the surfaces you're working with? A little more info ~might~ lead to some additional refinements or alternatives, especially with regard to curve creation / manipulation, if you want to investigate them.

Not a class project. Not terribly complex surfaces just a surface blended from sections. The component is a turbine airfoil.

I'm not familar at all with Scan Tools - perhaps it's not in our license.

I guess the bottom line is that you can't apply tangent conditions to curves imported from an IBL?

If this is the case I'm satisfied with the curve through point method. Any method that requires manually redefining the curves is not an option in this case because I'm iterating through several designs to reach an optimum solution. With the point through curve method I just read in new points and the curves update including the tangency and curvature constraints at the ends. In the end it took 2 days to run 15 models. Now that we've found a rough solution we will go back and manually generate style curves to ensure smooth curvature in the sections.

Thank you for all the help.

Help / Technical Support Info (for future reference).

I think that's a good assumption.

Sounds like a winner to me. Hope it goes well.