Modelling: spline on surface

[bmembme]

Hello,


I have been trying to create splineon afree-form surface (bone geometry) to create some extruded features over it. The surface of theboneis composedof a set of small patches (the solid geometry has been developped from a stl file using scanto3D plugin).


I tried using 'Spline on Surface' tool from the 'Sketch' menu but didn't get the desired spline. When selecting the second pointfor creatingthe spline, most of the time I get a message saying " placing a point on this surface will end previous spline creation and a new one will be started".


Could anyone pleaseput some light on this. Why do this message comes and how do Iget rid ofthis?Is there any alternate way to create extruded features onsuch surfaces? Any help and suggestionsis highly appreciated.


Thanks for your time.


With regards


bpal

 

[jimshaw]

bpal,


STL geometry is always a challenge to work with. First, make sure you import it as either a solid/surface budy, and not a graphics body, but it sounds like you may have already done this. I assume then that your model tree shows hundreds of individual surface bodies?


If so, then SWis treating each triangle as a separate surface, and thus "spline on surface" will not work for this. You could try to knit the surfaces together to solve this. Try small sections at first.


Other methods include: intersection curves, extruding surfaces, projection curves, split lines, etc. Are you familiar with these functions? Can you share a picture to give us a better idea of the geometry? Or even better, the stl file itself?


Jim Shaw
http://www.linkedin.com/in/shawengineering

 

[bmembme]

Dear Jim,



I have opened the stl file as solid/surface body; not as a graphics.


After converting the stl mesh geometry into 3D, I have got the following surface geometry (as attached in figure 1). In the model tree, I see only a single solid (named Imported1) that has multiple small pathces.
I tried to knit the surfaces (small pathces) together. It worked fine for small sections; however, I was not successful to knit all patches. Even I got the same erorr message while I tried to create spline on the knit-surfaces. So I guess, knitting the surfaces may not be a solution to this problem.


Though I am not very familiar with the functions you suggested, I 'll have look into those methods. For your better understanding, I tried to attach the stl file of the bone itself, but not able to upload due tolarger file size than that allowed.



View attachment 5913

2011-02-14_065618_Fig1.zip


Fig. 1 A and B: Tibia geomtery with small patches


Looking forward to your further suggestions about it.


Thank you very much!


With kind regards


B Pal

 

[jimshaw]

Bpal,


You have a single solid body, which is great. Knitting surfaces will not be needed.


I have offered a number of options to the spline-on-surface: intersection curves, extruding surfaces, projection curves, split lines, etc. Are you familiar with these functions?


In order to help further, we'd need to know what geometry you are looking to create. Can you share a sketch or something that describes your end goal? If you want to share the stl file privately, PM me...


Jim Shaw
http://www.linkedin.com/in/shawengineering

 

[bmembme]

Dear Jim,


Sorry about my late response to the post.


I would like to model some plates over the bone surface. Please see the attached pictures to have an idea how the geometry looks like.Its something about fracture fixation plates in orthopaedics. The plateshave curvature both in the radial and in the longitudinal direction of the bone. I have also attached the stl file of the femur bone for your convenience.Hope this helps you to understand what I am looking for.


In the mean time, I 'll explore the options you have suggested. 2011-02-18_130231_bone-plates.zip


Thanks a lot for your help and further comments.


With kind regards


BPal

 

[Canuck]

Hey BPal,

Could you model the bone plate. I am also looking for ways to model plates with dual curvature. I am working with Proximal Tibia Bone plates.

Thank you
Hina