How to view laser scan on navigation grid?

[thslr2154]

How to view laser scan data on top of map grid on ROS web interface? I can view using ROS3djs but i want to view it on ROS2djs. is it possible?

Thanks in advance

[MatthijsBurgh]

Seems like a laser scan is not implemented in ROS2D (yet). Feel free to add it.

[thslr2154]

Seems like a laser scan is not implemented in ROS2D (yet). Feel free to add it.

Do you have a reference site or an example file?

Thanks in advance

[MatthijsBurgh]

I think the classes in the models folder are the closest starting point.

[ghafour2016]

In Ros2djs it is not impleneted, but you can implement that like this function, I implemented and it is working properly:

function displayLaserScan() {  
    let marker_radius = 0.03;
    let marker_fill_color = createjs.Graphics.getRGB(255, 0, 0, 1.0);
    let laser_listener = new ROSLIB.Topic({
                                ros: local_ros, 
                                name: ROS_CONFIG.LASER_TOPIC,
                                messageType: 'sensor_msgs/LaserScan'});
    let prev_markers = null;
    laser_listener.subscribe(function(msg){
      const num = msg.ranges.length
      const angles = Array.from({length: num}, (_, i) => msg.angle_min + (msg.angle_max - msg.angle_min) / num * i);
      const poses_2d = angles.flatMap((angle, index) => {
          const range = msg.ranges[index];
          if (range > msg.range_min && range < msg.range_max) {
              return [[Math.cos(angle) * range, Math.sin(angle) * range, -angle]]
          }
          return []  // Skip this point
      });
      if (base_footprint_tf === null) {
          console.log('no tf');
          return;
        }
      // TODO: We might be able to apply the tf transform to the container itself, and dont have to do it on each pose.
      // Init the graphics component
      const scan_markers = new createjs.Container();
      const graphics = new createjs.Graphics().beginFill(marker_fill_color).drawCircle(0, 0, marker_radius).endFill();

      // Transform each point and add it to the graphics
      poses_2d.forEach(pt => {
          // pt[2] += Math.PI / 2
          const pose = new ROSLIB.Pose({
              position: new ROSLIB.Vector3({
                  x: pt[0], y: pt[1], z: 0
              }), orientation: new ROSLIB.Quaternion({
                  x: 0, y: 0, z: Math.cos(pt[2]), w: Math.sin(pt[2])

              })
        });
        pose.applyTransform(base_footprint_tf)  
        const marker = new createjs.Shape(graphics)
        marker.x = pose.position.x;
        marker.y = -pose.position.y;        
        marker.rotation = - getYawFromQuat(pose.orientation).toFixed(2);        
        scan_markers.addChild(marker)
      });

      // TODO: Just update the old one, dont make new ones everytime
      if (this.prev_markers !== null){
        viewer.scene.removeChild(prev_markers);
      }

      viewer.addObject(scan_markers);
      prev_markers = scan_markers;
    });
  }

[fllay]

how do I get base_footprint_tf and this function getYawFromQuat?

I got the laser scan display on the map but it seems that all points miss place.

I get base_footprint_tf from

   var tfClient = new ROSLIB.TFClient({
      ros: this.rbServer,
      angularThres: 0.01,
      transThres: 0.01,
      rate: 10.0,
      fixedFrame: "map",
      serverName: "tf2_web_republisher",
    });

    //console.log(tfClient);
    tfClient.subscribe(
      "base_footprint",
      function (tf) {
        //console.log(tf);
        this.base_footprint_tf = tf;
      }.bind(this)
    );

I got it working now. it is a TF between map frame and laser frame.

   var tfClient = new ROSLIB.TFClient({
      ros: this.rbServer,
      angularThres: 0.01,
      transThres: 0.01,
      rate: 10.0,
      fixedFrame: "map",
      serverName: "tf2_web_republisher",
    });

    //console.log(tfClient);
    tfClient.subscribe(
      "laser",
      function (tf) {
        //console.log(tf);
        this.base_footprint_tf = tf;
      }.bind(this)
    );

[ghafour2016]

Hi, the getYawFromQuat is:

function getYawFromQuat(q) {
  var quat = new Three.Quaternion(q.x, q.y, q.z, q.w);
  var yaw = new Three.Euler().setFromQuaternion(quat);
  return yaw["_z"] * (180 / Math.PI);
}

and you can get base_footprint_tf from this:

var base_footprint_tf = null;
var tf_client = new ROSLIB.TFClient({
    ros: ros, 
    fixedFrame: "map",
    angularThres: 0.01, 
    transThres: 0.01
  });
  tf_client.subscribe("/laser", function(tf) {   //Maybe /scan in your project
    base_footprint_tf = tf;
  }); 

[ghafour2016]

The result may be like this image:

[fllay]

My result is ok

However, I have to reduce the number of points 5 times. Otherwise, it will be very slow. My lidar gives about 1000 points. I observe that it can render about 200 points without slowing the system down.

[ghafour2016]

you can change poses_2d's flatmap in the code and replace poses_2d.forEach with for statement.

[ghafour2016]

I change the display laserscan() function to show half of points:

function displayLaserScan(ros) {
  // console.log('start laser scan');
  let topic =  ROS_CONFIG.LASER_TOPIC ;//"/sick_safetyscanners/scan";
  let marker_radius = 0.03;
  let marker_fill_color = createjs.Graphics.getRGB(255, 0, 0, 1.0);
  let laser_listener = new ROSLIB.Topic({
                              ros: ros, 
                              name: topic,
                              messageType: 'sensor_msgs/LaserScan'});
  let prev_markers = null;
  laser_listener.subscribe(function(msg){
    const num = msg.ranges.length
    const angles = Array.from({length: num}, (_, i) => msg.angle_min + (msg.angle_max - msg.angle_min) / num * i);
    const poses_2d = angles.flatMap((angle, index) => {
        const range = msg.ranges[index];
        if (range > msg.range_min && range < msg.range_max) {
            return [[Math.cos(angle) * range, Math.sin(angle) * range, -angle]]
        }
        return []  // Skip this point
    });
    if (base_footprint_tf === null) {
        console.log('no tf');
        return;
    }
    // TODO: We might be able to apply the tf transform to the container itself, and dont have to do it on each pose.
    // Init the graphics component
    const scan_markers = new createjs.Container();
    const graphics = new createjs.Graphics().beginFill(marker_fill_color).drawCircle(0, 0, marker_radius).endFill();

    // Transform each point and add it to the graphics
    //console.log('pose 2d',poses_2d.length);
    for(let i=0;i<poses_2d.length;i++){
      if(i%2 === 0){
        let pt = poses_2d[i];
        const pose = new ROSLIB.Pose({
          position: new ROSLIB.Vector3({
              x: pt[0], y: pt[1], z: 0
          }), orientation: new ROSLIB.Quaternion({
              x: 0, y: 0, z: Math.cos(pt[2]), w: Math.sin(pt[2])

          })
        });
        pose.applyTransform(base_footprint_tf);
        const marker = new createjs.Shape(graphics);
        marker.x = pose.position.x;
        marker.y = -pose.position.y;
        marker.rotation = viewer.scene.rosQuaternionToGlobalTheta(pose.orientation);

        scan_markers.addChild(marker);
      }
    }
    // TODO: Just update the old one, dont make new ones everytime
    if (this.prev_markers !== null){
      viewer.scene.removeChild(prev_markers);      
    }
    prev_markers = scan_markers;
    viewer.addObject(prev_markers);
  });
}  

[CursingThomas]

I change the display laserscan() function to show half of points:

function displayLaserScan(ros) {
  // console.log('start laser scan');
  let topic =  ROS_CONFIG.LASER_TOPIC ;//"/sick_safetyscanners/scan";
  let marker_radius = 0.03;
  let marker_fill_color = createjs.Graphics.getRGB(255, 0, 0, 1.0);
  let laser_listener = new ROSLIB.Topic({
                              ros: ros, 
                              name: topic,
                              messageType: 'sensor_msgs/LaserScan'});
  let prev_markers = null;
  laser_listener.subscribe(function(msg){
    const num = msg.ranges.length
    const angles = Array.from({length: num}, (_, i) => msg.angle_min + (msg.angle_max - msg.angle_min) / num * i);
    const poses_2d = angles.flatMap((angle, index) => {
        const range = msg.ranges[index];
        if (range > msg.range_min && range < msg.range_max) {
            return [[Math.cos(angle) * range, Math.sin(angle) * range, -angle]]
        }
        return []  // Skip this point
    });
    if (base_footprint_tf === null) {
        console.log('no tf');
        return;
    }
    // TODO: We might be able to apply the tf transform to the container itself, and dont have to do it on each pose.
    // Init the graphics component
    const scan_markers = new createjs.Container();
    const graphics = new createjs.Graphics().beginFill(marker_fill_color).drawCircle(0, 0, marker_radius).endFill();

    // Transform each point and add it to the graphics
    //console.log('pose 2d',poses_2d.length);
    for(let i=0;i<poses_2d.length;i++){
      if(i%2 === 0){
        let pt = poses_2d[i];
        const pose = new ROSLIB.Pose({
          position: new ROSLIB.Vector3({
              x: pt[0], y: pt[1], z: 0
          }), orientation: new ROSLIB.Quaternion({
              x: 0, y: 0, z: Math.cos(pt[2]), w: Math.sin(pt[2])

          })
        });
        pose.applyTransform(base_footprint_tf);
        const marker = new createjs.Shape(graphics);
        marker.x = pose.position.x;
        marker.y = -pose.position.y;
        marker.rotation = viewer.scene.rosQuaternionToGlobalTheta(pose.orientation);

        scan_markers.addChild(marker);
      }
    }
    // TODO: Just update the old one, dont make new ones everytime
    if (this.prev_markers !== null){
      viewer.scene.removeChild(prev_markers);      
    }
    prev_markers = scan_markers;
    viewer.addObject(prev_markers);
  });
}  

Hi, i know this is a while ago. But i am having trouble recreating your solution. Could you tell me if my html file should work?

<html>
<head>
<meta charset="utf-8" />

<script type="text/javascript" src="easeljs.min.js"></script>
<script type="text/javascript" src="eventemitter2.js"></script>
<script type="text/javascript" src="roslib.min.js"></script>
<script type="text/javascript" src="ros2d.js"></script>

<script type="text/javascript" type="text/javascript">
  /**
   * Setup all visualization elements when the page is loaded.
   */
  function init() {
    // Connect to ROS.
    var ros = new ROSLIB.Ros({
      url : 'ws://0.0.0.0:9090'
    });

    // Create the main viewer.
    var viewer = new ROS2D.Viewer({
      divID : 'viewer',
      width : 600,
      height : 500
    });

    function getYawFromQuat(q) {
  var quat = new Three.Quaternion(q.x, q.y, q.z, q.w);
  var yaw = new Three.Euler().setFromQuaternion(quat);
  return yaw["_z"] * (180 / Math.PI);
}

var base_footprint_tf = null;
var tf_client = new ROSLIB.TFClient({
    ros: ros, 
    fixedFrame: "map",
    angularThres: 0.01, 
    transThres: 0.01
  });
  tf_client.subscribe("/front/scan", function(tf) {   //Maybe /scan in your project
    base_footprint_tf = tf;
  }); 

  function displayLaserScan(ros) {
  // console.log('start laser scan');
  let topic =  "/front/scan" ;//"/sick_safetyscanners/scan";
  let marker_radius = 0.03;
  let marker_fill_color = createjs.Graphics.getRGB(255, 0, 0, 1.0);
  let laser_listener = new ROSLIB.Topic({
                              ros: ros, 
                              name: topic,
                              messageType: 'sensor_msgs/LaserScan'});
  let prev_markers = null;
  laser_listener.subscribe(function(msg){
    const num = msg.ranges.length
    const angles = Array.from({length: num}, (_, i) => msg.angle_min + (msg.angle_max - msg.angle_min) / num * i);
    const poses_2d = angles.flatMap((angle, index) => {
        const range = msg.ranges[index];
        if (range > msg.range_min && range < msg.range_max) {
            return [[Math.cos(angle) * range, Math.sin(angle) * range, -angle]]
        }
        return []  // Skip this point
    });
    if (base_footprint_tf === null) {
        console.log('no tf');
        return;
    }
    // TODO: We might be able to apply the tf transform to the container itself, and dont have to do it on each pose.
    // Init the graphics component
    const scan_markers = new createjs.Container();
    const graphics = new createjs.Graphics().beginFill(marker_fill_color).drawCircle(0, 0, marker_radius).endFill();

    // Transform each point and add it to the graphics
    //console.log('pose 2d',poses_2d.length);
    for(let i=0;i<poses_2d.length;i++){
      if(i%2 === 0){
        let pt = poses_2d[i];
        const pose = new ROSLIB.Pose({
          position: new ROSLIB.Vector3({
              x: pt[0], y: pt[1], z: 0
          }), orientation: new ROSLIB.Quaternion({
              x: 0, y: 0, z: Math.cos(pt[2]), w: Math.sin(pt[2])

          })
        });
        pose.applyTransform(base_footprint_tf);
        const marker = new createjs.Shape(graphics);
        marker.x = pose.position.x;
        marker.y = -pose.position.y;
        marker.rotation = viewer.scene.rosQuaternionToGlobalTheta(pose.orientation);

        scan_markers.addChild(marker);
      }
    }
    // TODO: Just update the old one, dont make new ones everytime
    if (this.prev_markers !== null){
      viewer.scene.removeChild(prev_markers);      
    }
    prev_markers = scan_markers;
    viewer.addObject(prev_markers);
  });
}  
}
</script>
</head>

<body onload="init()">
  <h1>Simple Map Example</h1>
  <div id="viewer"></div>
</body>
</html>```

[chang556]

i have same question。 i will show ('no tf');

[ghafour2016]

You must check the /front/scan or /scan, in the code we have: tf_client.subscribe("/front/scan", function(tf) { //Maybe /scan in your project base_footprint_tf = tf; }); if do not receive anything from client. it returns no tf.

[taj1290]

Can you please share the complete code as I am having issues in viewing laser scan on map? I have tried as per the above instructions but unable to view laserscan. Although I am able to view in Ros3Djs. Thanks in advance

[PVGanesh2000]

Can anyone explain...Me please how to work with this ROS WEB BRIDGE

Thanks in advance..

Am I need to launch any simulation package.. Then create any html file .. And how to visualize my robot in web .. Can anyone explain me please

[PVGanesh2000]

Help me which distro It was working...