AI Lines
What is fast_lane.ai?
The fast_lane.ai file tells AI opponents how to drive around your track. It contains:
- Racing Line - The optimal path AI cars will follow around the track
- Track Boundaries - Left and right edge limits that define where the AI can safely drive
- Speed Hints - Information about corners and straights for AI speed calculations
Without a fast_lane.ai file, AI opponents won't be able to race on your track.
Opening the AI Lines Editor
Click the AI Racing Line tool in the toolbar (🏎️ icon) to open the AI Lines panel. You'll need at least one road placed on your track.
Creating an AI Line
- Select a road - Choose which road to create the AI line from using the dropdown
- Copy Centerline - Click this button to create the racing line from your road's center
- Auto-Optimize - Automatically moves the racing line toward corner apexes for a faster line
Editing the Racing Line
The racing line appears as green markers connected by a green line. You can drag these markers to adjust the racing path:
- Drag a marker - Move just the racing line point (edges stay in place)
- Ctrl + Drag - Move the racing line AND both edge boundaries together
- Drag Influence slider - Controls how many neighboring points move along with your drag (creates smooth curves)
Editing Track Boundaries
Track edges appear as orange (left) and blue (right) markers. These define the safe driving area for AI:
- Drag an edge marker - Move that edge boundary point independently
- Drag Influence - Also applies to edge markers for smooth adjustments
The edges are completely independent from the racing line - you can adjust them without affecting the racing path.
Panel Controls
- Node Spacing - Distance between points along the line (smaller = more detail, larger = smoother)
- Optimization Strength - How aggressively Auto-Optimize cuts corners
- Drag Influence - Number of neighboring nodes affected when dragging (0-25)
- Show Track Edges - Toggle visibility of edge lines and markers
- Smooth Line - Apply smoothing to the racing line
- Resample - Redistribute points evenly along the line at current spacing
Exporting
Click Export fast_lane.ai to download the file directly, or the AI line will be included automatically when you export your track.
The exported file converts your 3D racing line and edge positions into the distances and data format that Assetto Corsa expects.
Tips for Good AI Lines
- Test your line - Drive the racing line yourself to make sure it's smooth and fast
- Use Auto-Optimize first - Start with optimization, then fine-tune manually
- Smooth corners - Make sure corners flow naturally without sharp kinks
- Edge boundaries - Keep edges at realistic track limits - not too tight, not too loose
- Higher node spacing - 1.5-2m is usually good; too many nodes can cause jittery AI behavior