Minimal working example for RViz marker publishing

asked 2021-03-11 05:22:53 -0500

Py
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Does anyone know of a complete minimal working example to publish a marker that can be visualised in RViz written in Python?

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answered 2021-03-11 06:11:07 -0500

Roberto Z.
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This is a minimal working example of a ROS node in Python with a Rviz marker publisher:

#! /usr/bin/env python

import rospy
from visualization_msgs.msg import Marker

rospy.init_node('rviz_marker')

marker_pub = rospy.Publisher("/visualization_marker", Marker, queue_size = 2)

marker = Marker()

marker.header.frame_id = "/map"
marker.header.stamp = rospy.Time.now()

# set shape, Arrow: 0; Cube: 1 ; Sphere: 2 ; Cylinder: 3
marker.type = 2
marker.id = 0

# Set the scale of the marker
marker.scale.x = 1.0
marker.scale.y = 1.0
marker.scale.z = 1.0

# Set the color
marker.color.r = 0.0
marker.color.g = 1.0
marker.color.b = 0.0
marker.color.a = 1.0

# Set the pose of the marker
marker.pose.position.x = 0
marker.pose.position.y = 0
marker.pose.position.z = 0
marker.pose.orientation.x = 0.0
marker.pose.orientation.y = 0.0
marker.pose.orientation.z = 0.0
marker.pose.orientation.w = 1.0

while not rospy.is_shutdown():
  marker_pub.publish(marker)
  rospy.rostime.wallsleep(1.0)

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That's really great, just what I needed! My next task is to colour code each marker according to a sensor value like a heat map. Any ideas how I'd achieve this?

Py ( 2021-03-15 14:27:49 -0500 )edit

I am glad that this resolved your question. To change to color of one marker use the attribute .color , it is shown above. For a heatmap it seems to me that you need many markers. Take a look at visualization_msgs/MarkerArray message. It is a bit broad subject to discuss here in details.

Roberto Z. ( 2021-03-15 14:48:28 -0500 )edit

For future readers: This wasn't working for me, I was getting the error For frame [/map]: Frame [/map] does not exist. After spending probably way too long on this, I realized that /map indeed does not exist in the tf tree (run rosrun tf view_frames to get a pdf of the tree) - but map IS in the tree. I changed the frame_id to map and then it worked.

TLRD: If your getting For frame [/map]: Frame [/map] does not exist try changing marker.header.frame_id = "/map" to marker.header.frame_id = "map"