[ros-users] small text for report which includes object detection

Fri Jul 16 09:59:40 UTC 2010

Hi Matei,

two more questions:
1. are the objects in
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo_worlds/meshes
compatible with the matching algortihm in tabletop_object_detector?

2. for testing the recognition algorithm, how easy is it to transform the meshes
back to pointclouds and deliberately alter them a bit?

Regards,
Rene

2010/7/14 Matei Ciocarlie <matei at willowgarage.com>:
> Hi Renee,
>
> For now you will have to add models to the database by hand - we will
> have some tutorials coming out probably next week on how to do that.
>
> Matei
>
> On Wed, Jul 14, 2010 at 3:14 AM, René Ladan <r.c.ladan at gmail.com> wrote:
>> Hi,
>>
>> is there currently any node available to input custom models?
>> The model_assembler node seems to have vanished in thin air.
>>
>> Regards,
>> Rene
>>
>> 2010/7/13 Matei Ciocarlie <matei at willowgarage.com>:
>>> That's hard to quantify precisely... I would say that you should not
>>> worry about precision too much, any reasonably lifelike mesh will do.
>>>
>>> It also depends what else is in the database of models: if you only
>>> have your own models, then only those will be fitted against. You will
>>> be able to recognize fewer objects, but at least other models will not
>>> get in the way. You can also play with the thresholds in
>>> tabletop_object_detector/src/tabletop_node.cpp to make the recognition
>>> more forgiving.
>>>
>>> Matei
>>>
>>> On Tue, Jul 13, 2010 at 9:24 AM, René Ladan <r.c.ladan at gmail.com> wrote:
>>>> Hi Matei,
>>>>
>>>> I get it now ;)
>>>>
>>>> If I want to model my own objects (for any reason), how precise and
>>>> complete must the triangle meshes be for the object detection to work?
>>>>
>>>> Regards.
>>>> Rene
>>>>
>>>> 2010/7/13 Matei Ciocarlie <matei at willowgarage.com>:
>>>>> Hi Rene,
>>>>>
>>>>> The models are stored in the database as triangle meshes. For display,
>>>>> we found it more clear to render them as wireframe rather than
>>>>> triangle meshes, as the wireframe still allows the original point
>>>>> cloud to show trough a little bit.
>>>>>
>>>>> The detection is done by comparing the perceived point cloud against
>>>>> the triangle mesh stored in the database.
>>>>>
>>>>> Best,
>>>>> Matei
>>>>>
>>>>> On Tue, Jul 13, 2010 at 9:03 AM, René Ladan <r.c.ladan at gmail.com> wrote:
>>>>>> Hi Matei,
>>>>>>
>>>>>> so the wireframe is only used for display reasons and to store the models
>>>>>> more efficiently in the database. Is the detection then realized by comparing
>>>>>> perceived pointcloud with the pointcloud version of the database models?
>>>>>>
>>>>>> Regards,
>>>>>> Rene
>>>>>>
>>>>>> 2010/7/13 Matei Ciocarlie <matei at willowgarage.com>:
>>>>>>> Hi Rene,
>>>>>>>
>>>>>>> That's generally correct, except for the transformation of the point
>>>>>>> cloud into wireframe. The tabletop_object_detector uses sensor data
>>>>>>> directly as point clouds. You might see a wireframe displayed on the
>>>>>>> screen but that's only after a database model has been recognized. The
>>>>>>> wireframe is that of the model, superimposed on the point cloud that
>>>>>>> has been recognized.
>>>>>>>
>>>>>>> Matei
>>>>>>>
>>>>>>> On Tue, Jul 13, 2010 at 4:59 AM, René Ladan <r.c.ladan at gmail.com> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> below is a text I intend to include in a report. Do I get the basic ideas right?
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>> Rene
>>>>>>>>
>>>>>>>> Object handling consists of several steps, which are performed by the
>>>>>>>> tabletop_object_detector (and other) nodes.
>>>>>>>> •       Get an image of the object (e.g. a pool ball) from e.g. a stereo
>>>>>>>> camera with texturing or e.g. a laser range finder.
>>>>>>>> •       Transform the image (either a stereo-photo or a “sphere” of
>>>>>>>> distances) into a point cloud. A point cloud is a collection of
>>>>>>>> points, where all points have a number of pre-defined attributes, like
>>>>>>>> spatial coordinates, color, or neighborhood density. Point clouds are
>>>>>>>> the universal data structures for performing 3-dimensional algorithms
>>>>>>>> within ROS. TODO: figure out the algorithm
>>>>>>>> •       Transform the point cloud into a wireframe. TODO: figure out which
>>>>>>>> algorithm is used for this.
>>>>>>>> •       Now that an approximate wireframe model of the object is available,
>>>>>>>> (because the camera images are probably imperfect), this model can be
>>>>>>>> compared to a database of existing, perfect wireframe models. Because
>>>>>>>> the models are stored as blobs in the database, the approximation is
>>>>>>>> done in the ROS node. The database is thus only used a storage
>>>>>>>> backend.
>>>>>>>> •       The comparison algorithm, given the actual model at one side and the
>>>>>>>> database models at the other side, is able to calculate the likelihood
>>>>>>>> that the presented object matches a or multiple objects in the
>>>>>>>> database (e.g. for a ping-pong ball, it could say “90% pool ball, 8%
>>>>>>>> bottle cap, and 2% unknown”).
>>>>>>>>
>>>>>>>> --
>>>>>>>> http://www.rene-ladan.nl/
>>>>>>>>
>>>>>>>> GPG fingerprint = E738 5471 D185 7013 0EE0  4FC8 3C1D 6F83 12E1 84F6
>>>>>>>> (subkeys.pgp.net)
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>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Matei Ciocarlie
>>>>>>> Research Scientist
>>>>>>> Willow Garage Inc.
>>>>>>> 650-475-9780
>>>>>>> _______________________________________________
>>>>>>> ros-users mailing list
>>>>>>> ros-users at code.ros.org
>>>>>>> https://code.ros.org/mailman/listinfo/ros-users
>>>>>>>
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>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Matei Ciocarlie
>>>>> Research Scientist
>>>>> Willow Garage Inc.
>>>>> 650-475-9780
>>>>> _______________________________________________
>>>>> ros-users mailing list
>>>>> ros-users at code.ros.org
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>>>>>
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>>>
>>>
>>> --
>>> Matei Ciocarlie
>>> Research Scientist
>>> Willow Garage Inc.
>>> 650-475-9780
>>> _______________________________________________
>>> ros-users mailing list
>>> ros-users at code.ros.org
>>> https://code.ros.org/mailman/listinfo/ros-users
>>>
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>
>
>
> --
> Matei Ciocarlie
> Research Scientist
> Willow Garage Inc.
> 650-475-9780
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