Windows points filtering

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geodezja3d_pl
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Windows points filtering

Post by geodezja3d_pl »

Hi,

I have a continous problem with cleaning points near the windows. I consider my project point clouds very dirty and the cleaning via clipping boxes does not solve the problem entirely. I scan with M70 and 3x quality.

It's quite easy to remove points which went through the window glass (outside the building outline) but it's almost impossible to remove those reflected (which are inside).

I tried the Dark Scan Points Filter in Scene 2018 with Threshold set to 400 but it seems to have completly no effect on point cloud.

Any suggestions with Scene filters parameters?

Regards,
Kuba
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Simon Judd
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Re: Windows points filtering

Post by Simon Judd »

Kuba

The best way I find, to filter reflection from windows and mirrors etc is to make a selection in the area of the window/mirror

and then to run the distance filter setting both ranges to zero.

Right click in the selection/ scan points/filter/distance filter

Simon
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Re: Windows points filtering

Post by neeravbm »

TagLabs has recently released a feature to clear noisy points near windows. See https://youtu.be/Ifw8Qat65Fw. Here's the thread for reference: viewtopic.php?f=89&t=14305.
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Re: Windows points filtering

Post by scankukai »

Hello,
neeravbm wrote: Mon Feb 25, 2019 3:23 pm TagLabs has recently released a feature to clear noisy points near windows. See https://youtu.be/Ifw8Qat65Fw. Here's the thread for reference: viewtopic.php?f=89&t=14305.
Well, our plane filter is very efficient to remove all the points that are in front or after a plane. But in this case, the dark points are on the window from what I see. It is much more difficult. Try to set the dark point filter at a higher value, let's say 700. It is still a low value, especially with the new models of Focus.

But thanks for sharing Neerav!
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Re: Windows points filtering

Post by Bengineer »

We've encountered similar problems, especially with the interior reflected points. The points originating from the windows will often stretch out hundreds of feet, and overlap with other points. I've found a nifty way to clean the points, but it needs to be done prior to creating the Project Point Cloud.

Identify the scans with that contain the window artifacts. Load and open each individual scan in 3D view. This will open a window with the viewpoint centered at the scanner, containing only the data from that scan. From here, you can rotate your view (don't translate) and select all of the points lying in the window regions with the polygon select, then delete.

It works better for projects with fewer scans because you have to operate on each scan individually. Because you are operating from the radial center, and only on a single scan, you can delete all of the points in the window region without affecting good points.

(Technically you could operate on cluster level, as long as the scans in the cluster are on the same side of the window plane in question, in which case use "Locate Scan" to center the viewpoint on each scanner.)

We've used this to good effect when scanning both the interior and exterior of vehicles. The window artifacts overlap with good points so we can't just use clipping boxes to clean it.

This is what it looked like before. The reflection artifacts are both inside and outside. We also had doors in the open position we wanted to remove.
BeforeCleaning.jpg
Here's an example selection from the view center of a scanner.
FromCenter.jpg
Here's the same selection from another viewpoint.
OtherView.jpg
Here it is after cleanup using the method above.
AfterCleaning.jpg
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Re: Windows points filtering

Post by geodezja3d_pl »

Thanks everybody.
I figured out that cloudcompare also can do the job.
It's scalar field and intensity value filtering.
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Re: Windows points filtering

Post by DavidL »

I'm sure you can get good results using filters, but I prefer the manual approach which is to simply go through every scan individually prior to PPC creation. Open the planar view of the scan, select around the window/mirror, view this selection in 3D and then delete the noise. Using a space mouse helps for accuracy.
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Re: Windows points filtering

Post by Simon Judd »

Hi All

All of the methods above will remove the points in question.

However the reason i like the distance filter approach is that it does not affect the grey scale image If you are pushing data out to Websharecloud.

the attached image shows 3 approaches.

the pane to the top left had a simple selection in the planar/quickview and scan points were deleted.

the panel to the right had points deleted from the individual 3d view - not not all points were included in the the selection and therefore some of the grey image remains.

The bottom 2 panel have had a selection made in planar/quickview (similar to the top left panel) but instead of deleting the scan points the distance filter was run setting the range to keep all points between distances of zero and zero. This approach removes the points but leaves the grey image intact for better presentation in Websharecloud.
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Re: Windows points filtering

Post by Simon Judd »

Sorry forgot to mention. This filter cannot be run on a 3d selection.

Request to Faro has been made on this one.

Simon
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Re: Windows points filtering

Post by Bengineer »

Hi Simon,

You made a good point about retaining the quality of the planar images for WebShare, and I think the original question has been answered sufficiently, but I would like to share these additional details. This pertains to Scene's behavior when deleting points under different circumstances. Here are a couple of scenarios I have tested.

If planar (or quickview) color is loaded, and a selection is deleted, the corresponding section of the color photo will also be deleted, but not in the greyscale photo.

If planar (or quickview) greyscale is loaded, and a selection is deleted, the corresponding section of the greyscale photo will also be deleted, but not in the color photo.

If a filter is applied to a selection in either planar view (or quickview), the data is deleted, but both photos remain unchanged.

If the points are deleted from the 3D view --while the scan is loaded-- the corresponding section of the color photo (if loaded in color), or greyscale photo (if loaded in greyscale), will also be deleted.

But if the points are deleted from the 3D view --while the scan is not loaded-- the data is deleted, but both photos remain unchanged.

The last point is useful if you want to keep the integrity of the photos, but also need to see the scan in 3D to identify the points that need deletion. It behaves the same way as a filter (insofar as it doesn't affect the photos), but in the 3D view.

Sorry for the exhaustive list, but it has been valuable to to know how Scene behaves under various circumstances.

-Ben
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