SampleConsensusInitialAlignment

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SampleConsensusInitialAlignment

KiaP
Hello Group,
I have been using SampleConsensusInitialAlignment for matching templates to a search cloud as described in the tutorial
http://pointclouds.org/documentation/tutorials/template_alignment.php#template-alignment

In some instances my templates match in other cases they don't.  I am trying to make sense of the parameters used in example.  But there is little documentation about them.  
I would like to start a discussion that would shed some light on it.  Please comment if you know what these parameters are:

FeatureCloud:
1) normal_radius_;  //the sphere radius used as the maximum distance to consider a point a neighbor
ok this is seems clear

2) feature_radius_;
how is this different from the one above?  feature vs. neighbor.  ??


These parameter really don't have any explanations. The best I could find was a comment which I added below.

TemplateAlignment
1) min_sample_distance_;
2) max_correspondence_distance_;
3) nr_iterations_;

Note: the maximum correspondence distance is actually specified as squared distance; for this example, we’ve decided to truncate the error with an upper limit of 1 cm, so we pass in 0.01 squared.

Any help is highly appreciated.

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Re: SampleConsensusInitialAlignment

andersgb1
Hi,

On Wed, Jul 1, 2015 at 9:51 PM, KiaP <[hidden email]> wrote:
Hello Group,
I have been using SampleConsensusInitialAlignment for matching templates to
a search cloud as described in the tutorial
http://pointclouds.org/documentation/tutorials/template_alignment.php#template-alignment

In some instances my templates match in other cases they don't.  I am trying
to make sense of the parameters used in example.  But there is little
documentation about them.
I would like to start a discussion that would shed some light on it.  Please
comment if you know what these parameters are:

FeatureCloud:
1) normal_radius_;  //the sphere radius used as the maximum distance to
consider a point a neighbor
ok this is seems clear

2) feature_radius_;
how is this different from the one above?  feature vs. neighbor.  ??

The normal radius refers to the size of the neighborhood used for estimating surface normals. The feature radius refers to the radius used for estimating the FPFH features (which underneath are using the precomputed normals for the surface to build the histograms).
 


These parameter really don't have any explanations. The best I could find
was a comment which I added below.

TemplateAlignment
1) min_sample_distance_;

During RANSAC pose estimation, triplets of corresponding points are sampled to generate a hypothesis pose. To avoid instabilities in this process, a minimal edge length between any two point in these triplets is enforced by this parameter.
 
2) max_correspondence_distance_;

This parameter is used in the base class pcl::Registration (http://docs.pointclouds.org/trunk/classpcl_1_1_registration.html) and is the Euclidean inlier threshold used during pose verification using the MSE.
 
3) nr_iterations_;

This is just the number of RANSAC iterations. 

 

Note: the maximum correspondence distance is actually specified as squared
distance; for this example, we’ve decided to truncate the error with an
upper limit of 1 cm, so we pass in 0.01 squared.

Any help is highly appreciated.





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Re: SampleConsensusInitialAlignment

KiaP
Thanks you so much for your response Andres..
This for sure helps understand the algorithms.   

On Thu, Jul 2, 2015 at 1:09 AM, andersgb1 [via Point Cloud Library (PCL) Users mailing list] <[hidden email]> wrote:
Hi,

On Wed, Jul 1, 2015 at 9:51 PM, KiaP <[hidden email]> wrote:
Hello Group,
I have been using SampleConsensusInitialAlignment for matching templates to
a search cloud as described in the tutorial
http://pointclouds.org/documentation/tutorials/template_alignment.php#template-alignment

In some instances my templates match in other cases they don't.  I am trying
to make sense of the parameters used in example.  But there is little
documentation about them.
I would like to start a discussion that would shed some light on it.  Please
comment if you know what these parameters are:

FeatureCloud:
1) normal_radius_;  //the sphere radius used as the maximum distance to
consider a point a neighbor
ok this is seems clear

2) feature_radius_;
how is this different from the one above?  feature vs. neighbor.  ??

The normal radius refers to the size of the neighborhood used for estimating surface normals. The feature radius refers to the radius used for estimating the FPFH features (which underneath are using the precomputed normals for the surface to build the histograms).
 


These parameter really don't have any explanations. The best I could find
was a comment which I added below.

TemplateAlignment
1) min_sample_distance_;

During RANSAC pose estimation, triplets of corresponding points are sampled to generate a hypothesis pose. To avoid instabilities in this process, a minimal edge length between any two point in these triplets is enforced by this parameter.
 
2) max_correspondence_distance_;

This parameter is used in the base class pcl::Registration (http://docs.pointclouds.org/trunk/classpcl_1_1_registration.html) and is the Euclidean inlier threshold used during pose verification using the MSE.
 
3) nr_iterations_;

This is just the number of RANSAC iterations. 

 

Note: the maximum correspondence distance is actually specified as squared
distance; for this example, we’ve decided to truncate the error with an
upper limit of 1 cm, so we pass in 0.01 squared.

Any help is highly appreciated.





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View this message in context: http://www.pcl-users.org/SampleConsensusInitialAlignment-tp4038743.html
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Re: SampleConsensusInitialAlignment

andersgb1
Very good :)

On Tue, Jul 7, 2015 at 8:33 PM, KiaP <[hidden email]> wrote:
Thanks you so much for your response Andres..
This for sure helps understand the algorithms.

On Thu, Jul 2, 2015 at 1:09 AM, andersgb1 [via Point Cloud Library (PCL)
Users mailing list] <[hidden email]> wrote:

> Hi,
>
> On Wed, Jul 1, 2015 at 9:51 PM, KiaP <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=4038744&i=0>> wrote:
>
>> Hello Group,
>> I have been using SampleConsensusInitialAlignment for matching templates
>> to
>> a search cloud as described in the tutorial
>>
>> http://pointclouds.org/documentation/tutorials/template_alignment.php#template-alignment
>>
>> In some instances my templates match in other cases they don't.  I am
>> trying
>> to make sense of the parameters used in example.  But there is little
>> documentation about them.
>> I would like to start a discussion that would shed some light on it.
>> Please
>> comment if you know what these parameters are:
>>
>> FeatureCloud:
>> 1) normal_radius_;  //the sphere radius used as the maximum distance to
>> consider a point a neighbor
>> ok this is seems clear
>>
>> 2) feature_radius_;
>> how is this different from the one above?  feature vs. neighbor.  ??
>>
>
> The normal radius refers to the size of the neighborhood used for
> estimating surface normals. The feature radius refers to the radius used
> for estimating the FPFH features (which underneath are using the
> precomputed normals for the surface to build the histograms).
>
>
>>
>>
>> These parameter really don't have any explanations. The best I could find
>> was a comment which I added below.
>>
>> TemplateAlignment
>> 1) min_sample_distance_;
>>
>
> During RANSAC pose estimation, triplets of corresponding points are
> sampled to generate a hypothesis pose. To avoid instabilities in this
> process, a minimal edge length between any two point in these triplets is
> enforced by this parameter.
>
>
>> 2) max_correspondence_distance_;
>>
>
> This parameter is used in the base class pcl::Registration (
> http://docs.pointclouds.org/trunk/classpcl_1_1_registration.html) and is
> the Euclidean inlier threshold used during pose verification using the MSE.
>
>
>> 3) nr_iterations_;
>
>
> This is just the number of RANSAC iterations.
>
> See more info in the class doc (
> http://docs.pointclouds.org/trunk/classpcl_1_1_sample_consensus_initial_alignment.html)
> and in the publication (
> http://files.rbrusu.com/publications/Rusu09ICRA.pdf).
>
>>
>
>
>> Note: the maximum correspondence distance is actually specified as squared
>> distance; for this example, we’ve decided to truncate the error with an
>> upper limit of 1 cm, so we pass in 0.01 squared.
>>
>> Any help is highly appreciated.
>>
>>
>>
>>
>>
>> --
>> View this message in context:
>> http://www.pcl-users.org/SampleConsensusInitialAlignment-tp4038743.html
>> Sent from the Point Cloud Library (PCL) Users mailing list mailing list
>> archive at Nabble.com.
>> _______________________________________________
>> [hidden email] <http:///user/SendEmail.jtp?type=node&node=4038744&i=1> /
>> http://pointclouds.org
>> http://pointclouds.org/mailman/listinfo/pcl-users
>>
>
>
> _______________________________________________
> [hidden email] <http:///user/SendEmail.jtp?type=node&node=4038744&i=2> /
> http://pointclouds.org
> http://pointclouds.org/mailman/listinfo/pcl-users
>
>
> ------------------------------
>  If you reply to this email, your message will be added to the discussion
> below:
>
> http://www.pcl-users.org/SampleConsensusInitialAlignment-tp4038743p4038744.html
>  To unsubscribe from SampleConsensusInitialAlignment, click here
> < > .
> NAML
> <
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