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How to make curved edges sharp

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Message 1 of 21
graham.dunn
4801 Views, 20 Replies

How to make curved edges sharp

Hi 

 

I am looking for some assistance with a project I am working on.  I am scanning footwear lasts in order for them to be scaled then carved. 

 

However, when I scan them I am losing the hard 90 degree edges which appear to be getting rounded off. I am using the structure sense scanner on an ipad and a handheld sense scanner using the sense software. 

 

Unfortunately, in order for them to be used, I need the edges to be sharper than the original model but due to the curved nature of the last I have been struggling to find an easy way to do it. 

 

Many thanks for any assistance 


Graham

The bottom corners that need to be sharp not roundedThe bottom corners that need to be sharp not roundedside.JPGbottom view.JPG

20 REPLIES 20
Message 2 of 21
ethancolbert
in reply to: graham.dunn

Hey Graham,

 

I've got a couple suggestions that might help, but I'm no expert so take these with a grain of salt.  I can think of a couple ways to go about creating sharper edges depending on how precise you need to be. 

 

Since you mention that they will be scaled and then carved, I am under the impression that the model doesn't have to be perfect.  If this is indeed the case, you could probably get by with some sculpting; a first pass with a 'draw' brush, and a second pass with a 'pinch' brush seems like a good choice, with either a 'linear' or 'spike' falloff.  Also, if you switch to 'surface' mode instead of 'volume' mode, the 'robust smooth' brush does a good job flattening faces.

 

If you do need something a bit more precise, I would turn to a CAD program.  I am only very familiar with Solidworks, so I'm not sure how well other software handles STL files.  That said, in Solidworks you can import the STL, create a reference plane approximately under the shoes surfaces, create a sketch on the plane, project the STL outline onto the sketch, and finally extrude the sketch up to the shoes body.  Looking at your model I'm guessing you'd have to do this three times to match the shape of the shoe.  After you export the model as an STL make sure to put it back into Meshmixer to inspect the meshing, as I have often found that Solidworks leaves holes and/or incorrectly flipped normals.

 

Let me know if you want any clarification on anything here.  I realize your post is a tad old, but figured I'd put this up anyways in the off chance that it would still be of use, or that it might help someone else with similar problems in the future.

 

Cheers,

Ethan

Message 3 of 21

Does anyone know how to solve the Problem ? Having the same one as the author!

Message 4 of 21
hfcandrew
in reply to: Adrian.Winkler

A) Get a better scanner (using a $300 dollar hobby scanner gives you hobby-like results)

B) Append a plane > Move plane to the orientation you want > Select the edge you want cornered off > Set target> Attract sculpting brush

Message 5 of 21
hfcandrew
in reply to: hfcandrew

Here is a screen cast of doing it: https://autode.sk/2lcJiSP

Message 6 of 21
Adrian.Winkler
in reply to: hfcandrew

Thanks for the advice, it helped me to create a sharp edge on simple, easy geometrys. But I want to create sharp edges on a Mass shoe last, specific on a insole edge. And there a simple plane will deform the shoes individuality. You might be right that the scanquality is not good enough. Maybe there is a sweep tool like in Parametic Creo, I dont know.

 

Message 7 of 21
MagWeb
in reply to: Adrian.Winkler

Reconstructing hard edges is some holy grail in mesh processing.

You might use the target idea posted by hfcandrew using curved targets too (if you're interested please post some example file) but that's not like sweeping you can do with a BRep (CAD) representation. A mesh as you get from a scan is always some representation based on arbitrary points of the scanning measurements without any mathematical structure. Therefor even the most costly scanner will put out rounded edges (more or less) and as there's no structure you'll need a process manually pushing its vertices.

---

Have a look at  TrippyLighting's thread over at the Fusion360 forum. He describes how to use Instant Meshes to generate a quad mesh from a triangle mesh. This quad mesh can be transformed to T-splines in Fusion to end up with a BRep .... hopefully



Gunter Weber
Triangle Artisan

Message 8 of 21
Adrian.Winkler
in reply to: MagWeb

edgeedge3D-Scan model3D-Scan modelThank you Magweb for the Information 🙂 Now im more relaxed cause I really hasseled to get a result and could not understand why u just dont sweep and cut the rest of the material loose. these two photos are from my 3D Scan foot model. the blue line is the edge that needs to be sharp. 

I will have a shot at your thread recommondation.

Message 9 of 21
hfcandrew
in reply to: Adrian.Winkler

Ya @MagWeb's is a good solution. For another MM solution I just thought of can you send me the .stl you have of the foot? I'll do a screen cast of it.

 

I'm a Pedorthist and work with foot orthotics so this is pretty applicable and useful for me.

Message 10 of 21
hfcandrew
in reply to: hfcandrew

Here is how to do it on a sphere: https://autode.sk/2mS32M3

Message 11 of 21
MagWeb
in reply to: hfcandrew

@hfcandrew 

This information might be useful for your attempt:

If you are in perspective view (orthographic view disabled in View menu) SelectVisible depends on how close the camera is to the object.

Here's some example (source file and .csv for my ToolManagerV3 script attached)

 

 



Gunter Weber
Triangle Artisan

Message 12 of 21
hfcandrew
in reply to: MagWeb

Amazing! Ya that could work too instead of contracting rings, although contracting rings is probably a bit more predictable/reproducible, but their are always many ways to go about solving the same problem in MM.

Message 13 of 21
MagWeb
in reply to: hfcandrew

Sorry @Adrian.Winkler  if this turns a to be a bit advanced. 

@hfcandrew : 

Yep, maybe expanding/contracting selections is a bit more intuitive. But: We know MM's focal length in perspective mode. This allows to set the cam's position/distance (via API) to where its eye rays hit an intended angular falloff of a surface . 

 



Gunter Weber
Triangle Artisan

Message 14 of 21
hfcandrew
in reply to: MagWeb

I think the contracting rings after the first 'Select Visible' is more consistent because if I'm using different models with different shapes, sizes, curvature and positions, then the surface falloff point will be different every time, whereas contracting 5 rings after a known starting point would give a more consistent result. But I'll test it out, see what I like better.

Message 15 of 21
MagWeb
in reply to: MagWeb

This is a possible workflow to "sharpen" edges to the outside.

 

It is based on a clean face group of what you consider as the sole.

Now it uses EDIT/MakePattern plus Booleans to construct geodesic distances.

The first go of MakePattern (in FaceGroupBorders-mode) constructs the center line of the region to be deformed later on.

The resulting pattern tube is welded with the source object using BooleanUnion and its face group is smoothed completely.

On the second go of MakePattern the diameter is slightly smaller than in its first go. This leaves a gap between both tubes. Running BooleanUnion on both tubes constructs two groups to be smoothed again. 

Now selecting the "gap -group" between and transforming it via SoftTransform sharpens the edge.

 

 



Gunter Weber
Triangle Artisan

Message 16 of 21
hfcandrew
in reply to: MagWeb

You never cease to amaze me, had to one up be with your MM wizardry!

 

I've never even really used that tool, that looks like it would be a pretty consistent method too. Thanks!

Message 17 of 21
Adrian.Winkler
in reply to: hfcandrew

Thank you both of you for your inspiration ! definitley some mastermind acting right there !

Message 18 of 21
MagWeb
in reply to: Adrian.Winkler

Here's another option assuming an existing group:

 

On a duplicate Smooth(in Membrane mode) one group.

That done discard the other group so only a membrane remains.

Extrude the membrane to both sides and create a facegroup at the lower side.

Do BooleanUnion and smooth out the transitions...

 



Gunter Weber
Triangle Artisan

Message 19 of 21
hfcandrew
in reply to: MagWeb

I propose a 'sharp edge corning' challenge for you:

 

Start with a primitive cylinder, then round the perimeter edge of one face using the robust smooth sculpt tool (kinda mimicking what happens to sharp edges in a scanned object) then use one of the above mentioned methods to restore it to its original shape.

Message 20 of 21
MagWeb
in reply to: hfcandrew

On a cylinder? Can't see a reason why the both methods above should not work (maybe Booleans might cause some problems due to near coplanar issues - such issues can be easily avoided).

But I think using these workflows is an overkill as the target shape is planar. So the only thing you'd need to do is to Extrude a selection of the base+rounded edge+ExpandRing using EndType Flat.



Gunter Weber
Triangle Artisan

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