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How to compare two point clouds?

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How to compare two point clouds?

Christian Mueller
Hello everybody,

I have general question about 3D point cloud perception, since I am not
really familiar in processing point clouds. I would like to measure the
similarity of two point clouds ... a kind of fitness score between a
reference point cloud and another point cloud.

Currently I am checking the literature, however I couldn't find a
"basic" algorithm. The only common way I found, is the alignment of both
points clouds by their center of mass. Afterwards one of the point cloud
is rotated till a best fit is achieved with the other point could.

Is there maybe some other approach or technique?

Thanks for any comment.

Christian




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Re: How to compare two point clouds?

Axelrod, Benjamin
I think ICP (Iterative Closest Point) is typically used to compare two
point clouds if they are not too dissimilar.  


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Christian Mueller
Sent: Friday, February 18, 2011 6:02 AM
To: [hidden email]
Subject: [ros-users] How to compare two point clouds?

Hello everybody,

I have general question about 3D point cloud perception, since I am not
really familiar in processing point clouds. I would like to measure the
similarity of two point clouds ... a kind of fitness score between a
reference point cloud and another point cloud.

Currently I am checking the literature, however I couldn't find a
"basic" algorithm. The only common way I found, is the alignment of both

points clouds by their center of mass. Afterwards one of the point cloud

is rotated till a best fit is achieved with the other point could.

Is there maybe some other approach or technique?

Thanks for any comment.

Christian




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Re: How to compare two point clouds?

Raymond Sheh
In reply to this post by Christian Mueller
Hi Christan,

I guess it really depends what the purpose of your comparison is. What
are you trying to do?

ICP and other related alignment techniques are useful if you're trying
to fit data to a model (eg. a new scan into an existing map, a possible
object into a scene, etc.) and generally also provides transform
information but if you're trying to do other things with your comparison
perhaps a different (and possibly simpler) technique may be more suited.

- Raymond

On 18/02/2011 7:02 PM, Christian Mueller wrote:

> Hello everybody,
>
> I have general question about 3D point cloud perception, since I am not
> really familiar in processing point clouds. I would like to measure the
> similarity of two point clouds ... a kind of fitness score between a
> reference point cloud and another point cloud.
>
> Currently I am checking the literature, however I couldn't find a
> "basic" algorithm. The only common way I found, is the alignment of both
> points clouds by their center of mass. Afterwards one of the point cloud
> is rotated till a best fit is achieved with the other point could.
>
> Is there maybe some other approach or technique?
>
> Thanks for any comment.
>
> Christian
>
>
>
>
> _______________________________________________
> ros-users mailing list
> [hidden email]
> https://code.ros.org/mailman/listinfo/ros-users

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Re: How to compare two point clouds?

Christian Mueller
On 02/18/2011 03:11 PM, Raymond Sheh wrote:

> Hi Christan,
>
> I guess it really depends what the purpose of your comparison is. What
> are you trying to do?
>
> ICP and other related alignment techniques are useful if you're trying
> to fit data to a model (eg. a new scan into an existing map, a possible
> object into a scene, etc.) and generally also provides transform
> information but if you're trying to do other things with your comparison
> perhaps a different (and possibly simpler) technique may be more suited.
>
> - Raymond
>
> On 18/02/2011 7:02 PM, Christian Mueller wrote:
>> Hello everybody,
>>
>> I have general question about 3D point cloud perception, since I am not
>> really familiar in processing point clouds. I would like to measure the
>> similarity of two point clouds ... a kind of fitness score between a
>> reference point cloud and another point cloud.
>>
>> Currently I am checking the literature, however I couldn't find a
>> "basic" algorithm. The only common way I found, is the alignment of both
>> points clouds by their center of mass. Afterwards one of the point cloud
>> is rotated till a best fit is achieved with the other point could.
>>
>> Is there maybe some other approach or technique?
>>
>> Thanks for any comment.
>>
>> Christian
>>
>>
>>
>>
>> _______________________________________________
>> ros-users mailing list
>> [hidden email]
>> https://code.ros.org/mailman/listinfo/ros-users
> _______________________________________________
> ros-users mailing list
> [hidden email]
> https://code.ros.org/mailman/listinfo/ros-users
>
Hi all,

thanks for the replies.
I am working at an object categorization project based on 3D information.
I would like to classify objects through their shape properties ( from
the object point cloud).
First I thought, I can try to fit some primitive shapes like cylinders,
spheres, cones, etc.
However most of the objects are not symmetric and more complex.
Hence I would like to create a kind of codebook of point-cloud-parts
from the entire point cloud of the object.
Later on, these point-cloud-parts could be compared with a query
point-cloud of an object in order to find a similarity.
However, to do so a reliable point-cloud similarity measure is required.
As far as I know, ICP might be not that good for this purpose, since a
good initial guess is required for a reliable alignment. Also the points
clouds which are supposed to be compared have to be  similar.

Christian
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Re: How to compare two point clouds?

Raymond Sheh
<snip>

> Hi all,
>
> thanks for the replies.
> I am working at an object categorization project based on 3D information.
> I would like to classify objects through their shape properties ( from
> the object point cloud).
> First I thought, I can try to fit some primitive shapes like cylinders,
> spheres, cones, etc.
> However most of the objects are not symmetric and more complex.
> Hence I would like to create a kind of codebook of point-cloud-parts
> from the entire point cloud of the object.
> Later on, these point-cloud-parts could be compared with a query
> point-cloud of an object in order to find a similarity.
> However, to do so a reliable point-cloud similarity measure is required.
> As far as I know, ICP might be not that good for this purpose, since a
> good initial guess is required for a reliable alignment. Also the points
> clouds which are supposed to be compared have to be  similar.
>
> Christian
> _______________________________________________
> ros-users mailing list
> [hidden email]
> https://code.ros.org/mailman/listinfo/ros-users

Perhaps have a look at techniques that find and compare the numbers and
characteristics of various descriptors (rather than the actual positions
of individual points). I've been out of this space for a little while so
I'm not sure what keywords are current ...
"spin images" spring to mind but of course there are many different
techniques out there.

- Raymond
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Re: How to compare two point clouds?

Christian Mueller
On 02/18/2011 03:39 PM, Raymond Sheh wrote:

> <snip>
>> Hi all,
>>
>> thanks for the replies.
>> I am working at an object categorization project based on 3D information.
>> I would like to classify objects through their shape properties ( from
>> the object point cloud).
>> First I thought, I can try to fit some primitive shapes like cylinders,
>> spheres, cones, etc.
>> However most of the objects are not symmetric and more complex.
>> Hence I would like to create a kind of codebook of point-cloud-parts
>> from the entire point cloud of the object.
>> Later on, these point-cloud-parts could be compared with a query
>> point-cloud of an object in order to find a similarity.
>> However, to do so a reliable point-cloud similarity measure is required.
>> As far as I know, ICP might be not that good for this purpose, since a
>> good initial guess is required for a reliable alignment. Also the points
>> clouds which are supposed to be compared have to be  similar.
>>
>> Christian
>> _______________________________________________
>> ros-users mailing list
>> [hidden email]
>> https://code.ros.org/mailman/listinfo/ros-users
> Perhaps have a look at techniques that find and compare the numbers and
> characteristics of various descriptors (rather than the actual positions
> of individual points). I've been out of this space for a little while so
> I'm not sure what keywords are current ...
> "spin images" spring to mind but of course there are many different
> techniques out there.
>
> - Raymond
> _______________________________________________
> ros-users mailing list
> [hidden email]
> https://code.ros.org/mailman/listinfo/ros-users
>

Right!,
I also thought about appearance based approaches which use statistical
features, like width, height, perimeter, curvatures, volume,.... etc. to
describe an object.
However the selected features might not be expressive enough to conclude
that an object is a cup, bowl, or box. That is one disadvantage, but
there are mostly computationally cheap.

One the other side the first approach (generating a codebook of parts
from a point-cloud of objects) relies strongly on a reliable point-cloud
similarity measure and I think this is a quite challenging task compared
to the generation of statistical features.


thanks,
  Christian





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Re: How to compare two point clouds?

rusu
Administrator
In reply to this post by Christian Mueller
Christian,

VFH is your friend: http://www.ros.org/wiki/vfh_cluster_classifier.

Cheers,
Radu.
--
http://pointclouds.org

On 02/18/2011 03:02 AM, Christian Mueller wrote:

> Hello everybody,
>
> I have general question about 3D point cloud perception, since I am not
> really familiar in processing point clouds. I would like to measure the
> similarity of two point clouds ... a kind of fitness score between a
> reference point cloud and another point cloud.
>
> Currently I am checking the literature, however I couldn't find a
> "basic" algorithm. The only common way I found, is the alignment of both
> points clouds by their center of mass. Afterwards one of the point cloud
> is rotated till a best fit is achieved with the other point could.
>
> Is there maybe some other approach or technique?
>
> Thanks for any comment.
>
> Christian
>
>
>
>
> _______________________________________________
> ros-users mailing list
> [hidden email]
> https://code.ros.org/mailman/listinfo/ros-users
_______________________________________________
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