Way to create outline (silhouette) of STL ?

john_trotto910

I know that for the most part you have to just use the Use command and try to get references from the STL and redraw it.
But, is there a way for a simple flat STL, (for example a flat plate with some holes in it) to auto generate an outline (silhouette) of it, or one of its faces?

Caden_Armstrong

I have a custom feature that does it for 3d objects
Silhouette custom feature

But for a 2d object, could you use an offset surface? Offset surface if you select some faces will make a new sheet body of the collective faces.

Derek_Van_Allen_BD

@Caden_Armstrong I learned the other day from @lana that opCreateOutlines supports cylinder and extrude face types as well, and from another exploration of bullying the sheet metal kernel that if something supports the extrude surface type it secretly also supports some spline surfaces if you check for the U or V curves being simple enough to do an extraction of the more complex curve, extrude, and replace face on the spline face to turn it into an extrude face.

I don't know if you'll ever need to do a silhouette on a spline face since it'll come out like a funhouse mirror effect but I dunno maybe there's a use case for someone out there.

Caden_Armstrong

https://forum.onshape.com/discussion/comment/125520#Comment_125520

I've been back and forth on allowing the other surface types, I have found that it isn't the most stable function. As is, opCreateOutline is marked as "internal use", and can have some crazy regen times. I feel like 99% of use cases are going to be planar anyways.

S1mon

https://forum.onshape.com/discussion/comment/125518#Comment_125518

Is there anything different/better about Silohoutte vs Project Body? Scanning the code, it seems like Project Body handles more cases (e.g. allowing faces).

https://cad.onshape.com/documents/201b33ee5450cefbca3b34b8/v/9028ee782ed5ec471178bca1/e/03f0c71d4856a8408c7766a0

Caden_Armstrong

https://forum.onshape.com/discussion/comment/125626#Comment_125626

I knew there was going to be an existing feature, I just couldn't find it.
Add this to the list of examples of how hard it is to find featurescripts.

I am planning to make an update to mine for approximated outlines. The base level function opCreateOutline can have some crazy regen time, and cause throw unexpected errors (it is marked for internal use only). Some use cases would prefer stability over accuracy.
But yes currently project body is more featured than the silhouette feature I threw together in 5 minutes.

S1mon

https://forum.onshape.com/discussion/comment/125628#Comment_125628

Yep. It's impossible to find anything.

A few use cases for these features that come to mind:

• Projected area to calculate approximate tonnage for injection molding. Definitely don't need super accuracy/precision for this since it's driving a small/medium/large sort of decision for machine choice. Ideally this could be done automatically along with volume to autopopulate standard drawing notes. For that, you definitely want something that calculates quickly.
• Frontal area for drag force calculations. I doubt these need to be perfect since the drag coefficient is an approximation of a theoretical property anyway.
• Packaging. Mostly likely any outline will get simplified in some way anyway.

john_trotto910

https://forum.onshape.com/discussion/comment/125518#Comment_125518

That looks like what I was after, however it will not let me select the STL file as the "part".

Same kinda issue with Offset Surfaces, it wont let me select just some surfaces of the STL, it picks the entire STL, and makes a sphere haha.