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Downsampled & non-colored pointclouds from D415

TBaum
Beginner
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Hello,

I'm using the Realsense D415 for onboard processing of the pointclouds on the Intel Aero Drone.

I have the issue, that the pointclouds are too large and are received at a too low frequency (around 7Hz). Is there any possibility to get a non-colored pointcloud from the Realsense D415? Also it would be great if the pointcloud could be downsampled such that I get smaller pointclouds but at a higher frequency. I'm using the ROS wrapper and tried to change a couple of parameters in the launch file and over rqt_reconfigure. But I could not achieve the desired behavior.

Previously I have been using the Realsense R200. There the pointcloud was non-colored by default and published at a rate of around 28Hz. It would be nice to get similarly sized clouds from the D415.

I'd be glad about any suggestions. Thanks,

Tanja

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MartyG
Honored Contributor III
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The discussion linked to below suggests setting the RGB to grayscale on the 400 Series using the Y16 format.

https://github.com/IntelRealSense/librealsense/issues/1554 How to change RGB stream to Grayscale? · Issue # 1554 · IntelRealSense/librealsense · GitHub

Regarding scaling down, you could use post-processing with a Decimation Filter.

https://github.com/IntelRealSense/librealsense/blob/development/doc/post-processing-filters.md# decimation-filter librealsense/post-processing-filters.md at development · IntelRealSense/librealsense · GitHub

SDK 2.0 has a post-processing sample program.

https://github.com/IntelRealSense/librealsense/tree/master/examples/post-processing librealsense/examples/post-processing at master · IntelRealSense/librealsense · GitHub

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TBaum
Beginner
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Thank you for your quick reply MartyG!

I looked into the links you sent me, but to be honest, I do not know how I would have to do that in my ROS setup.

I saw that the decimation filter in combination with the ROS wrapper is an open issue on Github. See: https://github.com/intel-ros/realsense/issues/313 No available methods to filter depth stream · Issue # 313 · intel-ros/realsense · GitHub

Also. ideally I would like to have not a grayscale pointcloud, but one without any color at all. But also grayscale would be better than rgb. However, the link you sent me also discussed this issue using the API, whereas I'm lookin for a solution using the ROS wrapper.

Do you have any suggestions?

Best,

Tanja

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MartyG
Honored Contributor III
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I was not able to find support for decimation filtering yet in ROS.

In regard to your other question about removing color in ROS ... a question was posted, with an accompanying script, where the problem was that they had a white point cloud. So their problem could end up being your solution if you make use of their "wrong" script.

https://answers.ros.org/question/268554/output-of-colored-point-clouds/ https://answers.ros.org/question/268554/output-of-colored-point-clouds/

Edit: apparently the white point cloud was due to something in Rviz rather than produced by the script. So that is not likely to be the solution. My apologies. I will keep looking,

Edit 2: one approach is to disable the color image in the launch file, as discussed here:

https://github.com/intel-ros/realsense/issues/347 No way to publish pointcloud without RGB · Issue # 347 · intel-ros/realsense · GitHub

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