# BAI

## Introduction

Each city may have one BAI-file. This file defines paths for controlling ambients such as pedestrians and automated traffic.

## Format description

### Intersections

A BAI-file is built up in three sections. The first section defines intersections.

### Roads

The next section defines all the routes between the intersections.

### Culling

Lists the roads to compute ambients for depending on the given PSDL block id. This section is divided into two parts, one for large AI-bubbles and one for small. Each part gives one list of road indices that are to be active for each block of the PSDL. Active means that AI computations are performed for the roads listed for the block that the player is currently on. The first list in each part should be ignored and thus set to a length of zero.

### Structure

In a pseudo-C style structure, a BAI-file looks like this:

struct BAI { char[4] header = "CAI1"; unsigned short nIntersections; // Number of intersections unsigned short nRoads; // Number of roads Road roads[nRoads]; // Roads Intersection intersections[nIntersections]; // Intersections Culling culling; // AI culling ("bubbles") };

struct Road { unsigned short id; unsigned short nSections; // Number of vertex sets unsigned short unknown0; // No idea unsigned short nBlocks; // Number of block references unsigned short blocks[nBlocks]; // References to the PSDL float unknown1; // Not sure. Speed threshold? float unknown2; // Always == 15 RoadData right; // Data for right side RoadData left; // Data for left side float distance[nSections]; // Distances between centre points of the road Vertex origin[nSections]; // Coordsys for tangent, origin Vector xOrientation[nSections]; // Coordsys for tangent, X axis Vector yOrientation[nSections]; // Coordsys for tangent, Y axis Vector zOrientation[nSections]; // Coordsys for tangent, Z axis Vector tangent[nSections]; // Direction of the road at each cross-section RoadEnd end; // End of the road RoadEnd start; // Start of the road };

struct Intersection { unsigned short id; unsigned short block; // Reference to the PSDL, (index + 1) Vertex center; // Center point of intersection unsigned short nRoads; // Number of connected roads unsigned long roads[nRoads]; // Clockwise ordered references to roads connected to this intersection };

struct Culling { unsigned long nBlocks; // Number of blocks in the PSDL + 1 CullingList cull0[nBlocks]; CullingList cull1[nBlocks]; };

struct CullList { unsigned short nRoads; unsigned short roads[nRoads]; // references to roads? }

struct RoadData { unsigned short nLanes; // Number of lanes unsigned short nTrams; // Number of tram rails (bool?) unsigned short nTrains; // Number of train rails (bool?) unsigned short unknown3; // Sidewalk? Always == 1 (bool?) unsigned short unknown4; // Road type? 0, 1, 2 or 3 float lanesDistances[nLanes][nSections]; // Distances for right lanes float distance[nSections]; // Outer edge distance float Unknown[11 + nLanes]; // Something about the lanes, gladly padded with 0xcdcdcdcd Vertex lLanesVertices[nLanes][nSections]; // Vertices for driving lane splines Vertex sidewalkCenter[nSections]; // Vertices for sidewalk central spline Vertex tramVertices[nTrams][nSections]; // Vertices for tram rail splines Vertex trainVertices[nTrains][nSections]; // Vertices for train rail splines Vertex sidewalkInner[nSections]; // Vertices for sidewalk inner spline Vertex sidewalkOuter[nSections]; // Vertices for sidewalk outer spline };

struct RoadEnd { unsigned long intersectionID; // Reference to Intersection[].id unsigned short unknown0; // Always 0xcdcd unsigned long vehicleRule; // See below unsigned long intersectionRoadIndex; // Index in the intersections road list or 0xcdcdcdcd Vertex trafficLightOrigin; // Origin of traffic light Vertex trafficLightAxis; // Orientation of traffic light };

struct Vertex { float x; float y; float z; }

struct Vector { float x; float y; float z; }

Values for *RoadEnd.vehicleRule*:

- 0 - Stop sign. The vehicles will stop, longest waiting vehicle drives first.
- 1 - Traffic light. One road at a time. All roads connected to the same intersection must have this control type, if not, the vehicles will behave as if it was a stop sign and the traffic light will blink between green and yellow. Traffic lights will only show up if their coordinates are not (0, 0, 0).
- 2 - Always stop. The vehicles stop and never proceed.
- 3 - Never stop. The vehicles will drive straight through the intersection without even slowing down.