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June 24, 2017, 16:38:57 pm


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Author Topic: Deleting Polygons Less than a Specified Area  (Read 417 times)
locus
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« on: January 11, 2017, 23:33:13 pm »

I've got a photo that I am attempting to CNC into a relief image.  The photo is of a family dog that is brindle.  Because the dog is brindle with a non-uniform coat color, the standard heightmap generator plugin in CB doesn't work very well.  I've tried many things from the list below alone and in combination to simplify the image without losing details but have not had much luck.  Things attempted so far are:

  • Reduce grayscale depth of photo.  It doesn't help unless I go down to two colors (black/white).  But then the image details go down the toilet.
  • Apply some blurring filter to the photo to smooth out the abrupt shading changes
  • Apply an embossing filter to the photo
  • Apply some edge detection filters to the photo

Finally, I converted the image to a true surface in CB  with Draw -Surface ->From Bitmap.  After converting the image, I then did Edit ->Surface ->Silhouette.  The attempt was to do some edge detection on the complex surface so I could set up some machining boundaries.  But the problem I have with this method is I end up with a ton of tiny polygons.  If I could delete all the tiny polygons, I think I would have some workable boundaries to machine.  In CB, is there an automated way to delete polygons less than a certain area?
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locus
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« Reply #1 on: January 11, 2017, 23:37:25 pm »

Project file attached.  Layer 1 is the originally surface created from the photo.  The Boundary layer is simply the outline of the dog's head.  And the Poly layer is the result of the silhouette operation.  In the Poly layer, you can see all those tiny polygons i'd like to remove.  I can delete them a few at a time, but it's very tedious.

* Clover-Profile.zip (2519.51 KB - downloaded 26 times.)
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dh42
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« Reply #2 on: January 11, 2017, 23:51:32 pm »

Hello

Maybe you can do some cleaning with file cleaner ?
http://www.cambam.co.uk/forum/index.php?topic=4924.0

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David

(and I see it is missing in the plugin web site, I'll repair this oversight  Embarrassed)

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dh42
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« Reply #3 on: January 11, 2017, 23:59:51 pm »

I've a try with you file, removing open/closed polyline  from 0 to 0.2 give a correct result, then you can use this plugin to try to smooth the rest.

http://www.atelier-des-fougeres.fr/Cambam/Aide/Plugins/PolylineSmooth.html

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David
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locus
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« Reply #4 on: January 12, 2017, 00:50:51 am »

Thanks a lot -playing around with both plugins now.
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Dragonfly
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« Reply #5 on: January 12, 2017, 09:29:05 am »

As I have said many times, you can make a reasonably good lithophane from a gray scale image, 'tuned' for that purpose with the help of an image editing program.
But a true relief, or more precisely bas-relief, can't be made automatically.
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