lukeb88's profile - activity

Hi!

In my task i need to detect the pose of an object (a cup in my case) because i have to grasp the cup with a robot.

I'm trying to catching the point cloud of the scene with ROS and a kinect. I thought to segment my point cloud that represent the scene, because i want to keep only the point of the cup. I have implemented a code in ROS that has a subscriber to detect the sensor_msgs/PointCloud2, then i transform the PointCloud2 in a pcl::PointXYZ.

And this is the code to the segmentation part:

pcl::ModelCoefficients::Ptr coefficients (new pcl::ModelCoefficients);
pcl::PointIndices::Ptr inliers (new pcl::PointIndices);
// Create the segmentation object
pcl::SACSegmentation<pcl::PointXYZ> seg;
// Optional
seg.setOptimizeCoefficients (true);
// Mandatory
seg.setModelType (pcl::SACMODEL_CYLINDER);
seg.setMethodType (pcl::SAC_RANSAC);
seg.setDistanceThreshold (0.01);
seg.setInputCloud (cloud);
seg.segment (*inliers, *coefficients);

it seems to work with a SACMODEL_PLANE, but with SACMODEL_CYLINDER this is the error that appears:

[pcl::SACSegmentation::initSACModel] No valid model given!
[pcl::SACSegmentation::segment] Error initializing the SAC model!
Could not estimate a planar model for the given dataset.

I found the various model here http://docs.pointclouds.org/1.7.0/gro...

Help me please!

P.S. And tell me if i'm trying to do the correct things for my task...

Tank You!

hi sudeep, now all work! thanks for your answer, it was really useful!

No other answers?

the rgb part work well! but i can't take the depth... i updated my question with my code!

i solved the last question using a subscriber that receive a sensor_msgs::PointCloud2 and then using pcl::fromROSMsg (*input, *cloud); But now my problem is that the depth it's always 0, i can't understand why...

for first thanks for your answer... In Ros i'm subscribed to this: ros::Subscriber sub = nh.subscribe< pcl::PointCloud<pcl::pointxyzrgb> >("/camera/depth_registered/points", 1, callback); because i discovered that i can directly subscribe a pcl::PointCloud insted of sensor_msgs::PointCloud, So if I understand correctly i have not to convert cloud data in pcl...

Hi!

I'm new of ROS and for an university project i have to grab a cup with a robot. For first i have to understand where the cup is. I have implemented an algorithm that segment the cup from the rest of the scene, and then it calculate the kaypoints of the new image. At this point i can determinate the "central" of my keypoints, that is broadly the centre of my cup.

The problem now is that till here i have worked with openCV and with the sensor_msgs/image, but to understand the depth of my pixel (the cup position) i need the registered depth topic.

What i couldn't understand it's: How i can subscribe the /camera/depth_registered/points (sensor_msgs/PointCloud2) to extract the RGB image (for the procedure that till here i did with sensor_msgs/image) and the depth image to know the depth of my task's pixel?

thanks

Luca

UPDATE

this is my callback

void callback(const sensor_msgs::PointCloud2::ConstPtr& msg) {
    pcl::PointCloud<pcl::PointXYZRGB>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZRGB>);
    pcl::fromROSMsg (*msg, *cloud);

    cv::Mat imageFrame;
    if (cloud->isOrganized()) {
        imageFrame = cv::Mat(cloud->height, cloud->width, CV_8UC3); 

        for (int h=0; h<imageFrame.rows; h++) {
            for (int w=0; w<imageFrame.cols; w++) {

                pcl::PointXYZRGB point = cloud->at(w, h);

                Eigen::Vector3i rgb = point.getRGBVector3i();

                imageFrame.at<cv::Vec3b>(h,w)[0] = rgb[2];
                imageFrame.at<cv::Vec3b>(h,w)[1] = rgb[1];
                imageFrame.at<cv::Vec3b>(h,w)[2] = rgb[0];

                int i = centre_x + centre_y*cloud->width;
                depth[call_count] = (float)cloud->points[i].z;

            }
        }
}

}//end callback

like you suggested to me. i tried to put the depth of my pixel in a vector, so i thought that i could see at least some values different to 0 (for the noise of the kinect i know that it's possible that some depth values in a point could be 0 or near 0 sometimes). But in my case all values still 0.