Scene 6.2 Cloud to Cloud reg, which points are used?

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sealund
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Scene 6.2 Cloud to Cloud reg, which points are used?

Post by sealund »

I have a project where i have scanned indoors but got alot of points of the outside through the windows. After processing the Scans in SCENE 6.2 they are marked as scan point clouds. If i just open the 3d views of the Scans and use the polygontool to remove the Points of the outside that i dont want to be used in the cloud to cloud registration, is that enough or do i have to load the Scans and remove the Points? Because when running Cloud to Cloud registration they are loaded, more or less depending on the subsampling setting?

Does anyone who know which points SCENE are using in Cloud to Cloud registartion?

//Erik
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Re: Scene 6.2 Cloud to Cloud reg, which points are used?

Post by flohrd »

You can remove the points in the way you are describing as scans are updated to be in sync with the point clouds once you save the project.
The result is identical to doing it the other way around where you load the scans and delete the points. In this case the point clouds would be updated to be in sync with the scan.
So either way it will remove the points permanently and the registration will no longer use them.
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Re: Scene 6.2 Cloud to Cloud reg, which points are used?

Post by sealund »

Ok, that´s good to know!

Thanks for fast reply! :)

//Erik
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Re: Scene 6.2 Cloud to Cloud reg, which points are used?

Post by SAttaya »

Daniel,

Can you answer Erik's other ?:
Does anyone who know which points SCENE are using in Cloud to Cloud registartion?
I thought that C2C was basically find vertical and horizontal planes
and register those together.

But based on the number of points compared in the scanManager results,
I don't think that is correct.
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Re: Scene 6.2 Cloud to Cloud reg, which points are used?

Post by flohrd »

Cloud 2 Cloud actually uses all scan points and does not rely on special geometry!
It basically looks at all the scan points and minimizes the three-dimensional position error between all the points for each scan pair.
Afterwards, a bundle adjustment is applied to minimize error propagation.
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Re: Scene 6.2 Cloud to Cloud reg, which points are used?

Post by SAttaya »

Daniel, so under ScanManager > scan point tensions > Used points
the number (typically 50K-70K-100K-120K) that shows is just
the number of points used in computing the statistics that are shown,
NOT the points used to do the C2C?
==================================================================================
Afterwards, a bundle adjustment is applied to minimize error propagation.
What is the bundle adjustment applied to if the c2c is between two (2) clouds (scans)?

<
Maybe I should have asked if the c2c was between multiple "adjoining" scans.
For example:
* 5 scans
-- 1 center scan (1/1)
-- 4 other scans (1/4) at 90°, 180°, 270° & 360°/0°

Assume:
* no overlap between the 1/4 scans that are 180° opposite each other
* 50% overlap between 1/1 to each of the other 4 scans
* 50% overlap between each 1/4 and it's two adjointing (+/- 90°) scans

so at a minimum
* 1/1 scan is adjacent to other 4 scans (4 C2Cs)
* scan at 90° is adjacent to 1/1, 360° and 180°, but not 270° (2 new C2Cs)
* scan at 180° is adjacent to 1/1, 90° and 270°, but not 360° (2 new C2Cs)
* scan at 270° is adjacent to 1/1, 180° and 360°, but not 90° (2 new C2Cs)
* scan at 360° is adjacent to 1/1, 270° and 90°, but not 180° (2 new C2Cs) (closes the loop)

does 6.2.2.7 do all of those C2Cs (4+2+2+2+2)?
is there some implied assumption of 4mm of noise/ranging error?
>

PS- thanks for the quick reply to my previous :?:
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