ROS2 RViz2 - Marker Publisher

Problem Statement

Implement a ROS2 node that publishes a visualization marker on the /visualization_marker topic at 1 Hz.

Requirements

Your node must:

• Create a publisher for visualization_msgs/Marker on /visualization_marker
• Use create_timer(1.0, ...) for the publish loop
• Set all mandatory Marker fields in every published message:
  • header.frame_id = 'map' and header.stamp from the node clock
  • ns (namespace string, any value)
  • id (integer, e.g. 0)
  • type = Marker.SPHERE (or CUBE, ARROW, CYLINDER, LINE_STRIP — your choice)
  • action = Marker.ADD
  • pose.position (x, y, z — any values)
  • pose.orientation.w = 1.0 (valid quaternion)
  • scale.x, scale.y, scale.z — all > 0 (scale of 0 makes the marker invisible)
  • color.r, color.g, color.b, color.a — all in 0.0–1.0 range, alpha must be > 0
• Log "Marker Publisher Ready" on startup

Input / Output

Output: visualization_msgs/Marker messages on /visualization_marker at 1 Hz

🤖 Why This Matters in Real Robots

RViz2 Markers are the primary tool for debugging perception and planning algorithms in the field. A robot engineer who can't publish markers can't visualize where their node thinks obstacles are, where the planned path goes, or what the sensor is seeing. In every robotics lab and company, "add a marker to see what's happening" is step 1 of any debugging process.

⚠️ Common Pitfalls

• alpha = 0: If color.a == 0 the marker is completely transparent and invisible in RViz2. It will also fail the test.
• scale = 0: Any scale dimension of 0 makes the marker degenerate. RViz2 will show a warning and not render it.
• Missing frame_id: Without a valid header.frame_id, RViz2 can't place the marker in any coordinate system.
• Forgetting header.stamp: Markers without a timestamp can't be synchronized with the TF tree.