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Understanding /camera/depth/points

asked 2015-01-28 14:08:05 -0500

gaussian gravatar image

updated 2015-01-29 10:39:18 -0500

What does the value in the 'data' field of the data published by /camera/depth/points represent? They are supposed to represent the distance of every pixel from the Kinect center point? How to I convert the data generated as point cloud into corresponding cartesian 3D coordinates ? An array of size [4915200x1] is generated. Which means distance to each pixel is represented using 16 entries in matrix (because 480 x 640 x 16 = 4915200). How do I understand this. Please explain the program behind visualization of this pointcloud data in rviz .

I kept my kinect in front of an plain 2D wall parallel with it. I thought that I will get a matrix with uniform value through out as the wall is equidistant from kinect. But I get a data which I could not understand and decode!

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answered 2015-01-29 10:43:33 -0500

dornhege gravatar image

The data is all the point clouds data fields (x, y, z) encoded into that array. Usually you don't read that by hand. Use a PCL Subscriber that allows you to directly get point data with x,y,z coordinates.

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Thanks a lot for your reply. I will go thro it.

gaussian gravatar image gaussian  ( 2015-01-29 11:03:10 -0500 )edit

i have converted pointcloud2 from kinect to pointcloudxyz. Are x,y,z coordinates in meters or mm?

dmngu9 gravatar image dmngu9  ( 2015-03-26 00:20:32 -0500 )edit

m ,

dornhege gravatar image dornhege  ( 2015-03-26 05:12:35 -0500 )edit

for the camera/depth/points topic. does it publish coordinates of pixel or world coordinate. Im a bit confused

dmngu9 gravatar image dmngu9  ( 2015-04-07 21:56:51 -0500 )edit

These are x,y,z points in the frame that is passed in the message header.

dornhege gravatar image dornhege  ( 2015-04-08 03:52:23 -0500 )edit

my frame id is camera_depth_optical_frame. are the xyz in my frame world coordinates? which will give depth from kinect to objects?

dmngu9 gravatar image dmngu9  ( 2015-04-08 08:43:05 -0500 )edit

They are very likely relative to the kinect sensor.

dornhege gravatar image dornhege  ( 2015-04-08 09:33:21 -0500 )edit

i still dont get what you mean

dmngu9 gravatar image dmngu9  ( 2015-04-08 19:39:19 -0500 )edit

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Asked: 2015-01-28 14:08:05 -0500

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Last updated: Jan 29 '15