Create Surface using Splines/Through Points? 3

[s89t3]

I am presently importing a 3D point cloud (about 170 3D points) into Unigraphics for the purpose of creating surface. I am able to create the surface using the "point cloud option". However I am unable to create the surface using the "through points option" because it says not enough rows for column degree. I would also like to create the surface using "splines" for i know how the points are connected in space. I am unable to do this because I cannot select the points I want.When I try, it appears that I have selected them but when I rotate the viewport it appears that the points were not selected at all.

Three questions are:

1)How do I create the surface using through points(and how do i make sure I am selecting the points that I want)?

2)How do I create the surface using splines?

3)Once a surface is created, is there a way to smooth the surface in UG?

Thanks in Advance

 

[cowski]

How many rows of points do you have? The error message "not enough rows for column degree" makes me think that you are either specifying too high of a degree or you only have 2 or 3 rows of points. As an example, a degree 5 spline requires a minimum of 6 defining poles (points).

I have never dealt with a point cloud, so I am not in a good position to answer your questions directly so I'll just give a few pieces of unsolicited advice

1) assuming your shape is more complicated than an extrude or revolve, you will want to look at free form operations (such as swept, through curve mesh, through curves, etc) which one you choose will depend on the complexity of your desired result and what you are going to use it for (if you need to match up to another surface, through curve mesh may be a good choice). If you have shape studio you will want to look at that as it gives even more options.

2) you will want to use the minimum required number of strings to define a surface - too many and you will get oscillations and other undesired artifacts.

3) I don't know about a smooth surface option in UG, but there is a smooth spline function. I don't have much experience with it, but I know there are a few pages devoted to it in the help files.

4) If you build the final result out of multiple surfaces, or if the surface you make needs to be curvature continuous with an existing surface you will need degree 5 splines (minimum).

5) Garbage In - Garbage Out

 

[Xwheelguy]

The tools you need to rebuild and smooth surfaces are included with Shape Studio (X-Form, Refit Face, Pole Smoothing, Match Edge).

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

 

[mjcole]

If you Do not have the Shape Studio license, the best option is as Cowski said the Through Curve mesh which gives you options for controling tangency at the ends of the surface. I have done some surfaces using this method and it worked fine, however I did set it up by putting the points on separate layers or in nemed groups so I could show or hide them to prevent incorectly picking points I did not want. You may also use copy to layer to keep the original cloud on the same layer.

I'm not sure if Surface through point cloud remains parametric with the Basic UG licenses but I'm not sure it's been some time since I've looked into it.

A good tip for creating the splines is to make sure you zoom in really close and check each one. Another tip would be to create your splines with the same minnimum number of points because you can edit the points and delete any extras at the end of the spline easily during feature creation or afterwards.

Michael

 

[Xwheelguy]

In case it hasn't been stressed enough, pay close attention to your splines. You want your splines to all be similar in terms of degree and segments for each surface, and preferably all surfaces. If you spend the time developing high quality splines, you will spend less time trying to smooth out surfaces. Just like cowski posted, Garbage In, Garbage Out (meaning if your splines are garbage, then your surfaces probably will be as well).

Also, use your Analysis tools to determine the quality of the curves and surfaces as you create them. If you have to, call GTAC and have them teach you how to use Curve Analysis Curvature Comb, Face Analysis (aka FA) Radius, FA Slope and FA Reflections over the phone. You won't regret it.

I feel one of the best tools UGS has added to NX is the Studio Spline. It can be made to be associative and you can assign up to G2 (Curvature) continuity at the ends. Play around with it and don't be too afraid to double click on the handles and see what neat little things can be done. Studio Spline is great for matching up to ends of sketch curves too. I can't stand the spline functionality in sketcher because it only allows for G1 (Tangent) continuity, so in place of sketching splines, I use Associative Studio Splines to meet up at the end points of sketch curves. If the sketch changes, then so does my spline.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com