Visualization Topics Reference

This document describes all visualization topics available in the F1Tenth multi-agent racing simulation. All visualizations are published as ROS2 topics and can be viewed in RViz2.

Quick Reference

Topic	Type	Default	Description
/racecar_labels	MarkerArray	Enabled	Name labels above each racecar
/speed_markers	MarkerArray	Disabled	Speed text above each racecar
/velocity_arrows	MarkerArray	Disabled	Velocity direction arrows
/safety_zones	MarkerArray	Disabled	Collision proximity indicators
/race_markers	MarkerArray	Enabled	Start/finish line
/lap_point	MarkerArray	Enabled	Checkered finish line (settable)
/obstacles	MarkerArray	Enabled	Spawned obstacles
/racecarN/trajectory	Path	Disabled	Historical path per racecar
/race_stats_json	String	N/A	JSON race statistics

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Detailed Descriptions

1. Racecar Labels (/racecar_labels)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Same as sensor publish rate (20-40 Hz)

Displays the name of each racecar floating above it. Labels are color-coded to match each racecar's assigned color.

Marker Properties:

• Type: TEXT_VIEW_FACING
• Height: 0.5m above ground
• Text: "racecar1", "racecar2", etc.

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2. Speed Markers (/speed_markers)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Same as sensor publish rate (20-40 Hz)

Displays the current speed (m/s) of each racecar as floating text. Color changes based on speed:

Speed Range	Color
0-1 m/s	Green
1-2 m/s	Yellow
2+ m/s	Red

Marker Properties:

• Type: TEXT_VIEW_FACING
• Height: 0.8m above ground
• Format: {speed:.1f} m/s

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3. Velocity Arrows (/velocity_arrows)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Same as sensor publish rate (20-40 Hz)

Displays velocity vectors as arrows pointing in the direction of travel. Arrow length is proportional to speed.

Marker Properties:

• Type: ARROW
• Scale: Length = speed × 0.5, width = 0.1m
• Color: Same as speed markers (green → yellow → red)

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4. Safety Zones (/safety_zones)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Same as sensor publish rate (20-40 Hz)

Transparent cylinders around each racecar indicating collision proximity. Based on minimum laser scan distance.

Min Scan Distance	Color
> 0.5m	Green (safe)
0.3m - 0.5m	Yellow (warning)
< 0.3m	Red (danger!)

Marker Properties:

• Type: CYLINDER
• Radius: 0.5m
• Height: 0.1m
• Alpha: 0.3 (transparent)

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5. Race Markers (/race_markers)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Published once (latched)

Static start/finish line visualization. Includes:

• White line strip at x=-1.0, spanning y=[-2.0, 2.0]
• "START / FINISH" text label

Marker Properties:

• Line Type: LINE_STRIP
• Text Type: TEXT_VIEW_FACING
• Position: Fixed at origin area

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6. Lap Point (/lap_point)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Published once, re-published when moved

Checkered finish line marker that can be dynamically positioned via the multiagent plugin.

Features:

• Classic checkered flag pattern (black/white squares)
• "FINISH" text label
• 4m wide, 0.5m deep
• Position settable via plugin dropdown → "Set Lap Point"

To Set Custom Lap Point:

1. In the Multiagent Plugin, select "Set Lap Point" from dropdown
2. Use RViz's "2D Pose Estimate" tool
3. Click on the map where you want the finish line
4. Lap time calculations automatically update

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7. Obstacles (/obstacles)

Type: visualization_msgs/MarkerArray
Frame: map
Rate: Published on change

Cylindrical obstacles spawned via RViz's "Publish Point" tool.

Features:

• Red semi-transparent cylinders
• Radius: 0.15m (configurable in code)
• Affect laser scans (racecars see them)
• Cause collision disqualification on contact
• Clear all via "Clear Obstacles" button in plugin

To Spawn Obstacles:

1. In RViz toolbar, click "Publish Point" (crosshair icon)
2. Click anywhere on the map
3. Obstacle appears at that location

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8. Trajectory Paths (/racecarN/trajectory)

Type: nav_msgs/Path
Frame: map
Rate: 5 Hz

Historical path showing the last 500 positions of each racecar. Separate topic per racecar.

Topics:

• /racecar1/trajectory
• /racecar2/trajectory
• /racecar3/trajectory
• etc.

Display in RViz:

1. Add → By topic → /racecarN/trajectory → Path
2. Adjust line width and color as desired
3. Default: disabled to reduce visual clutter

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9. Race Stats JSON (/race_stats_json)

Type: std_msgs/String
Rate: Same as sensor publish rate

JSON-formatted comprehensive race statistics for programmatic consumption.

Schema:

{
  "timestamp": 1234567890.123,
  "num_agents": 3,
  "simulation_running": true,
  "simulation_paused": false,
  "agents": [
    {
      "id": 1,
      "name": "racecar1",
      "position": {
        "x": 1.23,
        "y": 4.56,
        "theta": 0.78
      },
      "speed": 2.5,
      "min_scan_distance": 1.2,
      "current_lap_time": 15.3,
      "best_lap_time": 14.8,
      "disqualified": false
    }
  ]
}

Used By:

• Multiagent Plugin status indicator (Racing/Idle/Paused/Stopped)
• External monitoring tools

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Enabling Visualizations in RViz

Most visualizations are disabled by default to optimize performance. To enable:

1. Open RViz2 panel
2. Click "Add" button
3. Select "By topic"
4. Navigate to the desired topic
5. Select the appropriate display type (MarkerArray, Path, etc.)

Recommended for Low-End Systems:

• Keep only /racecar_labels and /race_markers enabled
• Disable LaserScan displays
• Set Target Frame Rate to 10 FPS

Full Visualization Setup:

• Enable all MarkerArray topics
• Enable trajectory paths for detailed analysis
• Useful for debugging and demo presentations

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Color Palette

Racecars are assigned colors from this palette (cycles for >10 agents):

Index	Color	RGB
0	Orange	(1.0, 0.5, 0.0)
1	Cyan	(0.0, 1.0, 1.0)
2	Magenta	(1.0, 0.0, 1.0)
3	Lime	(0.5, 1.0, 0.0)
4	Pink	(1.0, 0.4, 0.7)
5	Teal	(0.0, 0.5, 0.5)
6	Lavender	(0.7, 0.5, 1.0)
7	Brown	(0.6, 0.3, 0.0)
8	Olive	(0.5, 0.5, 0.0)
9	Navy	(0.0, 0.0, 0.5)