STL Import

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eric5935

Newbie

posts: 11

Registered: 2013-11-7

Message 1 of 4

 STL Import
16-05-2014 02:59 . am | View his/her posts only
After importing an STL file (let's use a T-Rex for this example from https://www.thingiverse.com/thing:73484/#files), I can tessellate the model, but I can't figure out how to get the curve tools to trace the outside of the shell (step #3) so I can convert it into a shape.

Any pointers?


You can follow this basic procedure to section scan data (from CMMs), point cloud data and imported STL data.
  • 1. Import the scan data (from CMMs), point cloud data, STL data or activate a part that contains point cloud data created by ZW3D.


  • 2. Use the [url="]Tessellate and Stitch a Set of Points or STL Data
    [/url] command to tessellate the STL or point data into connected triangles.


  • 3. Define a region on the tessellated data using a set of curves. This is done by using any of the existing 3D curve tools such as the [url="]Curve through Points[/url]
    command and "tracing" along the tessellated data.


  • 4. Use the [url="]Collect Nodes from Tessellated Data[/url] command to collect the point data that is "enclosed" by the boundary curves you created in step 3 above.


  • 5. Use the [url="]Fit Face[/url] command to fit a surface through the points collected in step 4 using the curves from step 3 as the boundaries.




Thanks,
Eric

Rank: 2

davej

Assistant Engineer

posts: 72

Registered: 2013-1-16

Message 2 of 4

16-05-2014 04:40 . am | View his/her posts only
Reply 1# eric5935

Eric,

Hope I'm wrong but I think the complexity of the t-rex model is beyond the practical use of the point cloud tools in ZW3D. Coming up with a smooth water tight surface model could be complex beyond description. It was when I tried to do a similar project. I strongly wish that someone can prove me wrong on this. There are surface creation automation tools there but in my opinion they tend more towards kinda flat slab type shapes (like the faces in the demos and videos) versus needing to shrink wrap surfaces 360 degrees around a swoopy complex shape.


The above being said I did translate your stl file in and had no problems attaching to vertices and/or points (after execution of the group command) to create curves such as Through Point Curves or Point Cloud Curves. I'm assuming from your comments that your goal is to use curves as boundaries for a bunch of patches that later could be sewn together. Free Form commands such as Curve Mesh, FEM Patch or N-sided patch. ??

You mentioned tessellation so I'm assuming you have the version of ZW3D that includes the Point Cloud tab with the dozen on so special point cloud commands. Make sure that you almost all the time work in wire frame view mode so that you can always see the vertices or points. And make sure that your snapping is turned on.

Won't be easy but you should be able to attach to and create curves.

There can be many variations as to what everyone needs as the end result but I ended up using the data that was there as a template/reference/guideline to create a feature based solid model with history versus a collection of surfaces that though accurate are mostly impossible to change.

Rank: 1

eric5935

Newbie

posts: 11

Registered: 2013-11-7

Message 3 of 4

16-05-2014 12:07 . pm | View his/her posts only
Thanks for the reply Dave.
>Coming up with a smooth water tight surface model could be complex beyond description.
Sounds like this may be an area for future development. 3D scanning of a an object, tweaking the design, and then printing on a 3D printer is becoming more common as the price of 3D printers drops.


>There can be many variations as to what everyone needs as the end result but I ended up
>using the data that was there as a template/reference/guideline to create a feature based
>solid model with history versus a collection of surfaces that though accurate are mostly
>impossible to change.
I agree that is the best way to go for typical mechanical parts, but in my case, I would like to either scan in existing parts or load in an STL file, make some changes to it, and then fabricate a prototype. So far, it looks like using external tools to do this is the best way, although it's entirely possible that I'm missing a step to do the translation in ZW3D.


By the way Dave, you have a very nice selection of videos on Youtube - keep up the great work!


Thanks,
Eric

Rank: 2

davej

Assistant Engineer

posts: 72

Registered: 2013-1-16

Message 4 of 4

17-05-2014 01:16 . am | View his/her posts only
Reply 3# eric5935

Eric,

There are many "use case" scenarios for anything that has the term 3D printing in it. Unfortunately for complex CAD programs the cheap and quick and dirty mentality associated with 3D printing doesn't fit very well.


While the complex shrink wrapping of surfaces (this is a mathematical nightmare) over point clouds needs to be left for the specialized applications (i.e., Geomagic and others) depending on your use case there are nice point cloud tools in ZW3D.


The magic and hard to define term you used was "tweaking".


If your use case allows the tweaking of selected areas the combination of the curve tools, the surface tools, along with the grouping functionality can allow nice tweaking. So in this use case we are tweaking selected areas of the point cloud data and sending it back out as a *.stl for 3D printing. As long as you have some design leeway and are not fighting tight tolerances quite a lot can be accomplished.


This selective tweaking without needing to turn everything into surfaces or solids in my opinion is what the point cloud tools on ZW3D do a good job at and are meant for.


Thanks for your comment about the YouTube videos. Note that I've not created all those videos. I've categorized and put existing videos in playlists to allow easy access.
See also