Filter glass and mirror points

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smacl
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Re: Filter glass and mirror points

Post by smacl »

yankoch wrote: Mon Sep 19, 2022 10:50 am Hi,

We developed specific plugins for Scene that delete everything behind windows or mirrors.

These plugins allow you to create custom polygonal planes. You don't need to create them in every scan.
Then, we have a filter that automatically erases everything behind each polygon. This is a batch calculation, you don't need to do anything once the filter starts.

This works very well if you have points behind windows or mirrors.
We put something very similar into SCC but found it doesn't work that well for mirrors unless you also have the setup information / observer position for each point. The problem is that points in the mirror in any given room can appear as points in another room. Removing mirrored points needs to be able to distinguish points in one room, observed from another room, such that they can be removed but the valid points in that room remain. Leandre Robitaille kindly supplied a good test data set for this purpose, which included an inclined mirror, shiny tv screen and a few other semi-reflective surfaces. Before this, I'd made the false assumption that mirrors would most likely be vertical on a parallel plane to the nearest wall. Alas, not so...

Once you have the setup information and the bounds of your mirrored surface, you can use ray tracing to eliminate the reflected points more effectively. Handy enough with static scanning but something of a computational nightmare on SLAM and mobile mapped scans. I'm sure someone cleverer than myself could train an AI to search for reflective surfaces in a pano image which could be another route to investigate.
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Re: Filter glass and mirror points

Post by yankoch »

smacl wrote: Mon Sep 19, 2022 1:46 pm We put something very similar into SCC but found it doesn't work that well for mirrors unless you also have the setup information / observer position for each point. The problem is that points in the mirror in any given room can appear as points in another room. Removing mirrored points needs to be able to distinguish points in one room, observed from another room, such that they can be removed but the valid points in that room remain. Leandre Robitaille kindly supplied a good test data set for this purpose, which included an inclined mirror, shiny tv screen and a few other semi-reflective surfaces. Before this, I'd made the false assumption that mirrors would most likely be vertical on a parallel plane to the nearest wall. Alas, not so...

Once you have the setup information and the bounds of your mirrored surface, you can use ray tracing to eliminate the reflected points more effectively. Handy enough with static scanning but something of a computational nightmare on SLAM and mobile mapped scans. I'm sure someone cleverer than myself could train an AI to search for reflective surfaces in a pano image which could be another route to investigate.
The plugin still works well with mirrors because it does the calculation scan by scan. For each scan, it takes into account the polygon geometry and the location of the scanning position.
The scanning position in the next room will also use the plane, but as there is nothing to delete behind, it will be ignored.
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Re: Filter glass and mirror points

Post by nichlasholm »

yankoch wrote: Mon Sep 19, 2022 4:10 pm The plugin still works well with mirrors because it does the calculation scan by scan. For each scan, it takes into account the polygon geometry and the location of the scanning position.
The scanning position in the next room will also use the plane, but as there is nothing to delete behind, it will be ignored.
Would your plugin be apple to help in situations like mine??
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Re: Filter glass and mirror points

Post by yankoch »

nichlasholm wrote: Tue Sep 20, 2022 5:13 am Would your plugin be apple to help in situations like mine??
Hello,
Probably.
If most points are located behind windows (either reflections or points captured through the glass), it will work without problems.
You won't lose any good points.
I recently used the plugins in an environment full of windows. I only had to create the planes in some scans, and it worked for the whole project.

I'd have a question: once your scans are cleaned, what is your workflow?
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Re: Filter glass and mirror points

Post by nichlasholm »

yankoch wrote: Tue Sep 20, 2022 11:37 am I'd have a question: once your scans are cleaned, what is your workflow?
For the most part i create a digital twin in revit, why you ask?? :)
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Re: Filter glass and mirror points

Post by yankoch »

nichlasholm wrote: Tue Sep 20, 2022 12:43 pm For the most part i create a digital twin in revit, why you ask?? :)
Well, you could have used the cleaned scans to stay in Scene and generate a webshare project.
If the goal is to leave Scene and import the scans in Revit, we also have another affordable solution to clean your scans with ScanSap. Its multi-clipping feature allows cleaning massive point clouds very quickly.
Most softwares have one clipping box, others offer the ability to create several boxes, but this is not very user friendly. We can create 100 boxes in minutes to hide unwanted areas and then export the result in Recap format.

If you are ok, you can send me your project (folders including revisions + lsproj file) and I'll send you the cleaned scans back. For free of course.
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