Hello,
I want to compare two fitted planes based on their parameters (normal vector and orthogonal distance to P(0/0/0)). Therefore i checked, if i can use the given center of the planes to calculate the orthogonal distance (ax+by+cz=d), by comparing the result (d) with the distance of a manual picked Point of the plane (Point Picking). By donig that i found out that the in the point picking progress shown normal vector isn the same as the calculated normalvektor of the plane. There is a slightly difference. Is there any Reason for that ?
Thank you for your answer!
Different normal vector in the plane parameters an point picking of a plane
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timbuktu55
- Posts: 2
- Joined: Thu Nov 05, 2020 8:54 am
Re: Different normal vector in the plane parameters an point picking of a plane
Where do you read the plane center? (or is the bounding-box center?)
And by the way, we have the 'Edit > Plane > Compare' tool (since v2.11 at least) that might be of interest to you.
And by the way, we have the 'Edit > Plane > Compare' tool (since v2.11 at least) that might be of interest to you.
Daniel, CloudCompare admin
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timbuktu55
- Posts: 2
- Joined: Thu Nov 05, 2020 8:54 am
Re: Different normal vector in the plane parameters an point picking of a plane
Thank you for you Quick response!
I read the Plane center and the normal vector out of the Plane Properties (right click on the Plane in the DB Tree -> Edit) as shown in picture a attached. Is the center only the center of the Box and not a point on a plane ?
The second thing i was wondering why the shown normal Vektor in the plane Properties ist different to the shown normal vector of a random picked ponint of this Plane.
And thank you for your advice with the Compare Tool! Next to the Dip DIrections, what distance ist there calculated? Isnt the distance bewtween the Centers of two Planes meaningless to Compare Planes? So in this case the Solution would be dependent on which part of a plane surface is segmented.
Or is the shown distance calculated by other parameters?
I read the Plane center and the normal vector out of the Plane Properties (right click on the Plane in the DB Tree -> Edit) as shown in picture a attached. Is the center only the center of the Box and not a point on a plane ?
The second thing i was wondering why the shown normal Vektor in the plane Properties ist different to the shown normal vector of a random picked ponint of this Plane.
And thank you for your advice with the Compare Tool! Next to the Dip DIrections, what distance ist there calculated? Isnt the distance bewtween the Centers of two Planes meaningless to Compare Planes? So in this case the Solution would be dependent on which part of a plane surface is segmented.
Or is the shown distance calculated by other parameters?
- Attachments
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- Ponint_picking.PNG (32.21 KiB) Viewed 1588 times
Re: Different normal vector in the plane parameters an point picking of a plane
No it was just to be sure. The center in this 'Plane properties' dialog is the right one.
The normal vector displayed in the 2D label is actually the interpolated normal of the triangle that is used to represent the plane. This is why you have small differences. But you should of course prefer the plane normal (from the plane properties). We should definitely improve that (i.e. use the real plane normal when available, and not the 'generic' triangle normal).
And the distances computed by the 'Plane comparison' tool are:
- the orthogonal distance between the second plane center and the first plane (i.e. along the first plane normal)
- the orthogonal distance between the first plane center and the second plane (i.e. along the second plane normal)
In the general case they are different, this is why CC computes and displays both. There's not a unique distance between two planes (unless they are parallel).
The normal vector displayed in the 2D label is actually the interpolated normal of the triangle that is used to represent the plane. This is why you have small differences. But you should of course prefer the plane normal (from the plane properties). We should definitely improve that (i.e. use the real plane normal when available, and not the 'generic' triangle normal).
And the distances computed by the 'Plane comparison' tool are:
- the orthogonal distance between the second plane center and the first plane (i.e. along the first plane normal)
- the orthogonal distance between the first plane center and the second plane (i.e. along the second plane normal)
In the general case they are different, this is why CC computes and displays both. There's not a unique distance between two planes (unless they are parallel).
Daniel, CloudCompare admin