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

[René Ladan]

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/
>>>>
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>>>
>>>
>>>
>>> --
>>> Matei Ciocarlie
>>> Research Scientist
>>> Willow Garage Inc.
>>> 650-475-9780
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>
>
>
> --
> Matei Ciocarlie
> Research Scientist
> Willow Garage Inc.
> 650-475-9780
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