Keeping only internal points of a cylindrical shape

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Mike H
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Keeping only internal points of a cylindrical shape

Post by Mike H » Wed Jul 04, 2018 1:22 pm

I have a scan of a screen that has voids that allow scan points to pass through as noise data. Is there an easy way to clean away the noise outside of the cylinder and keep only the inside points?

We have the tank module to 3dReshaper which works great on solid tanks but I cannot find a good way to clean away noise to only leave the inside face.ImageImage

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Re: Keeping only internal points of a cylindrical shape

Post by gilles_3Dreshaper » Wed Jul 04, 2018 1:47 pm

Hi Mike,

in order to split the points inside a cylinder from those outside the cylinder, just follow the following steps:
  • create the cylinder
  • select the point cloud and the cylinder
  • launch the command Cloud / Separate with object
  • select the option "Separate the inside and the inside"
  • choose which points you want to keep (inside, or outside, or both)
Gilles
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http://www.3dreshaper.com

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Mike H
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Re: Keeping only internal points of a cylindrical shape

Post by Mike H » Wed Jul 04, 2018 2:03 pm

Gilles,

I have no way of creating an accurate best fit cylinder since the cloud still has noise data, it's hard to explain. Using the attached photo of the object I scanned, I'm looking to show the deformation of just the inside face of the cylindrical object(washer screen). I'm getting noise data that is extending outside the object that is giving me trouble creating a best fit cylinder and an accurate mesh.

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Re: Keeping only internal points of a cylindrical shape

Post by gilles_3Dreshaper » Wed Jul 04, 2018 2:20 pm

ok!
then, maybe you can try:
  • create a cylinder by clicking a few points in the inside of the screen (using construct / Cylinder / Draw)
  • use this cylinder to keep only the points close to the cylinder using cloud / Separate with object (using "separate using a tolerance" option)
  • finally, use the same cylinder to keep only the points which local normals are similar to the local normal of the cylinder using cloud / Separate with object (using "separate using object orientation", use cloud estimated normal)
the final step will work if you have enough points locally in the parts you want to keep
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Re: Keeping only internal points of a cylindrical shape

Post by Phill » Sat Jul 07, 2018 12:50 pm

Mike

Gillies seem to have a pretty good workflow there. An alternative might be

1. Rough in the cylinder so you've got some numbers for unfurl
2. Use unfurl to make the cylinder into a flat plane
3. Import flat cylinder back into cyclone
4. Use region grow -> smooth surface
5. Use insert copy of objects point to separate out the cylinders points
6. Export and Refurl
7. Make your magic in reshaper

Alternatively you might be able to use las tools to make a ground surface once you have unfurled the data, which would sample the low points (requires a bit of mucking around with coordinate systems of course)

These are the options I'd be looking at if it was my job.

See link to unfurl/refurl post
viewtopic.php?f=23&t=4154&start=30

Lastools
https://rapidlasso.com/lastools/lasground/

Cheers

Phill

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Mike H
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Re: Keeping only internal points of a cylindrical shape

Post by Mike H » Sat Jul 07, 2018 2:12 pm

Phill wrote:Mike

Gillies seem to have a pretty good workflow there. An alternative might be

1. Rough in the cylinder so you've got some numbers for unfurl
2. Use unfurl to make the cylinder into a flat plane
3. Import flat cylinder back into cyclone
4. Use region grow -> smooth surface
5. Use insert copy of objects point to separate out the cylinders points
6. Export and Refurl
7. Make your magic in reshaper

Alternatively you might be able to use las tools to make a ground surface once you have unfurled the data, which would sample the low points (requires a bit of mucking around with coordinate systems of course)

These are the options I'd be looking at if it was my job.

See link to unfurl/refurl post
viewtopic.php?f=23&t=4154&start=30

Lastools
https://rapidlasso.com/lastools/lasground/

Cheers

Phill
Thanks Phil. I was thinking of smooth surface but it didn't work on a cylinder. I will use the unroll in CloudCompare, smooth surface in Cyclone and export surface pts to 3dreshaper.

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