[ros-users] FYI Kinect hacked driver for linux

[Ivan Dryanovski]

Same question as Stefan - has anyone thought of a calibration
procedure between the depth and range camera?

Ivan

On Fri, Nov 12, 2010 at 3:19 AM, Stefan Kohlbrecher
<stefan.kohlbrecher at googlemail.com> wrote:
> Nice, that already looks pretty good. Do you have the same ~4cm
> vertical offset between color and depth data?
> http://img717.imageshack.us/img717/3955/kinectrviztrevor.png
> It's pretty visible when looking at the screen in the lower portion.
> I'm well aware that this is basically uncalibrated, my question is
> more directed towards the variability of alignment between different
> Kinect devices.
>
> 2010/11/12 Alex Trevor <atrevor at gmail.com>:
>> Apologies for the broken github link, the correct one is:
>> https://github.com/atrevor/kinect_node.git
>> On Fri, Nov 12, 2010 at 2:20 AM, Alex Trevor <atrevor at gmail.com> wrote:
>>>
>>> Wow, looks like quite a few people are working on kinect nodes; we should
>>> probably combine efforts!  We’ve also been working on a kinect node for ROS
>>> based on Hector Martin’s driver, available at:
>>> git://github.com/atrevor/kinect_node.git
>>>
>>> Short youtube rviz screencap:
>>> http://www.youtube.com/watch?v=IxRIL1izvDs
>>>
>>> We assume that you have libfreenect from Hector Martin’s repo in the same
>>> parent directory (../libfreenect w.r.t. kinect_node):
>>> git://git.marcansoft.com/libfreenect.git
>>>
>>> So far, it publishes the camera image, as well as a PointCloud2 of
>>> PointXYZRGBs.  The RGB camera’s image is projected onto the range data,
>>> resulting in a color point cloud.  We calibrated the RGB camera, but haven’t
>>> yet calibrated the range camera -- since we can’t just use our normal
>>> checkerboard calibration target for this :) .  As Ivan and Stefan noted, the
>>> ranges we get are a little odd -- they definitely don't seem to be linear.
>>>  We calibrated it so the range is approximately correct at 2m for our
>>> sensor, but I agree that we really need to know how these work to make much
>>> progress. We'll probably do some testing shortly with targets at various
>>> ranges to attempt to address this.  Any input would be greatly appreciated!
>>> On Thu, Nov 11, 2010 at 5:41 PM, Stefan Kohlbrecher
>>> <stefan.kohlbrecher at googlemail.com> wrote:
>>>>
>>>> > 1. Is the depth image really 640x480, or is that oversampled? The
>>>> > wikipedia page states the depth sensor has an resolution of 320×240
>>>> > pixels. If it's oversampled, where does that take place - in the
>>>> > driver, or the device itself? I prefer not inflating the point cloud
>>>> > with oversampled data
>>>> I think the device itself reports the data with this size. If you look
>>>> at the picture I posted in the second post you also see that there are
>>>> for example one pixel sized holes in the 640x480 sized depth image,
>>>> which should not exist if some very simple interpolation scheme would
>>>> be used to blow up a 320x240 image to 640x480.
>>>> From what I read beforehand, the original Project Natal was supposed
>>>> to be 640x480, then Microsoft reportedly "downgraded" to 320x240 for
>>>> cost reasons (see
>>>>
>>>> http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=kinect+downgraded+to+320x240).
>>>> Now the sensor appears to deliver 640x480 again, which might or might
>>>> not be just blown up 320x240on the onboard ASIC.
>>>>
>>>> > 2. What is the relationship between the values in the depth_frame and
>>>> > the distance in meters? It doesn't appear to be linear
>>>> That´s really the interesting question, along with others like how to
>>>> calibrate visual and depth image to get real RGB-D data. With the
>>>> current state of affairs one can generate some impressive looking
>>>> images, but to leverage the full potential of the sensor these
>>>> calibration questions really have to be solved.
>>>>
>>>> > 3. I read somewhere the device's range can be set dynamically. I'm
>>>> > guessing one of the inits in inits.c could be responsible for the
>>>> > range.
>>>> That´s more stuff that will probably be discovered in the coming
>>>> days/weeks. Still very impressive how good the sensor works already
>>>> right out of the box.
>>>>
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>>
>>
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