How to get pointcloud2 data from usb_cam or Pointgrey camera?

asked 2015-05-11 05:28:32 -0500

david059
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Hello, experts~ I am a new in ROS. And recently, I am trying to get image and make it detected by the node ar_track_alvar. However, this ar node requires sensor_msgs/PointCloud2 data. Firstly I tried to use usb_cam_node and I got sensor_msgs/Image. The same situation happened using Pointgrey camera with its driver: pointgrey_camera_driver. After searching some files, I find that it might work if I can use openni to get the image, after all it is discribed in wiki: "Launch files to open an OpenNI device and load all nodelets to convert raw depth/RGB/IR streams to depth images, disparity images, and (registered) point clouds."here. And after I run the command: " roslaunch openni2_launch openni2.launch " it says there is no device. I really don't know how to make it out. Can anyone help me answer the following question: 1. Can pointgrey camera be directly used by openni launch file? 2. Can common USB camera be used by openni launch? 3. If the answer of both is negative, how can I get pointcloud2 data with what kind of device and with which driver? P.S. Here is what shell says after I run roslaunch openni2_launch openni2.launch

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answered 2015-05-11 06:02:59 -0500

KDROS
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updated 2015-05-11 06:07:11 -0500

For using openni package and also for generating point cloud you should have Kinect or Asus Xtion ( Depth Sensor). OpenNI wont work with normal usb camera. usb_cam package is to capture rgb image using usb camera.

For generating pointcloud u can use either Kinect with freenect package or rgbdslam ( available for electric Older version of ROS)

If you are only interested in creating 3D, you can use lsd_slam or ORB slam, it will give nice 3d in real time but it wont publish any pointcloud message.

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WOW! So quick! Thank you very much for your guidance! So now I understand what can be used for OpenNI and what cannot. But can I take it that the pointcloud can just only be generated by OpenNI which means I have to have devices you mentioned? Is there any other way I can get pointcloud with uabcam?

david059 ( 2015-05-11 06:22:35 -0500 )edit

Yup I mentioned, lsd_slam and ORB_Slam you can get good pointcloud, but for very good pointcloud either use lsd_slam with global shutter camera with fish eye lens or Kinect/Asus Xiton with freenect/openNI2 package.

KDROS ( 2015-05-11 06:32:49 -0500 )edit

I think you just really did me a great favor! Even though I can't find LSD_SLAM nor ORB_SLAM in http://www.ros.org/browse/list.php , I find them in github! I will try them right now and I hope this time I can make it. Thank you, KDROS!

david059 ( 2015-05-11 07:00:50 -0500 )edit

Thanx, Yup It is not available in ROS, check this links lsd_slam. You can ask if you will be in trouble.

KDROS ( 2015-05-11 11:21:23 -0500 )edit

Hey KDROS, after reading about what it says in github, I realize the problem you mentioned , LSD_SLAM indeed can not be used for live-pointcloud use in ROS. ButI think I find another way to get PointCloud2 data. By using image_proc

david059 ( 2015-05-12 10:40:36 -0500 )edit

I will talk in more detail in my answer below

david059 ( 2015-05-12 10:42:48 -0500 )edit

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answered 2015-05-12 10:55:28 -0500

david059
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To obtain sensor_msgs/PointCloud or sensor_msgs/PointCloud2 data, I think there is an easy way to realize it. No matter what your camera_driver is, there will always have Image_raw data. I use PointGrey carema and usb camera, both drivers of them can get raw image whose format is sensor_msgs/Image. Next use image_proc http://wiki.ros.org/image_proc?distro... we can get Image_rect [Image] which is the data format needed in the next step. I find depth_image_proc can produce PoindCloud or PointCloud2 data by using Image_rect. Here: http://wiki.ros.org/depth_image_proc . I think this is a way worthy of trying, even though I don't know what kind of image will finally get. I'm trying now, and I will update this question informing any one who see this question. Welcome everyone to come to discuss.

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Flow is good.. I will also try this, its very cheaper approach. Thanx. But till now I am using lsd_slam and kinect and getting good result.

KDROS ( 2015-05-12 11:22:32 -0500 )edit

Is it working fine ? In my case am getting error manager arg need to be set, I rectified this by giving true.. and there is no node/launch file for depth_image_proc. Tell me the detail execution process, it sounds interesting. I was using this package earlier but that time also i was unable to solve

KDROS ( 2015-05-13 00:59:37 -0500 )edit

I just get it through, you have to write a launch file according to the nodelet_plugins.xml file in depth_image_proc. You have to run a nodelet and here is the tutorial, I can get some thing in RVIZ, but still some trouble in ar_track

david059 ( 2015-05-13 01:30:27 -0500 )edit

I run image_proc, it is running successfully but its not publishing any topic. are you getting this? did you change any thing in launch file except manager arg?

KDROS ( 2015-05-13 03:59:41 -0500 )edit

if you are running a node, run this ROS_NAMESPACE=my_camera rosrun image_proc image_proc. my_camera is the relative name provided by your camera driver there will have topic shown in http://wiki.ros.org/image_proc?distro... Nodes section.

david059 ( 2015-05-13 10:35:35 -0500 )edit

If you roslaunch a launch file you have to rectify the original launch file, assign specific arg value like args="load image_proc/debayer $(arg manager) $(arg bond)" you need replace $(arg manager) with standalone_nodelet, like tutorial in the [](http://wiki.ros.org/nodelet/Tutorials/Running%20a%20n

david059 ( 2015-05-13 10:38:46 -0500 )edit

Main benefit of lsd_slam over this is that it fuses all pointcloud (like PCL) but in image_proc it is just publishing pointcloud for each image. which is easily doable by Kinect.

KDROS ( 2015-05-14 00:45:10 -0500 )edit

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