2) vehicles.xml — declare the driving behavior properties (same name as entity_class): The MUST match the exactly. All driving properties are optional — every one has a sensible default. ═══════════════════════════════════════════════════════════════════════════════ UNITY PREFAB — WHEEL ARRAY ORDER (CRITICAL) ═══════════════════════════════════════════════════════════════════════════════ Wheels must be assigned to the vehicle's wheels array in this exact order: Index 0 → Left wheel, Axle 1 (front-left) Index 1 → Right wheel, Axle 1 (front-right) Index 2 → Left wheel, Axle 2 (mid-front-left / rear-left on 4-wheel) Index 3 → Right wheel, Axle 2 (mid-front-right / rear-right on 4-wheel) Index 4 → Left wheel, Axle 3 (mid-rear-left) ← 6-wheel minimum Index 5 → Right wheel, Axle 3 (mid-rear-right) Index 6 → Left wheel, Axle 4 (rear-left) ← 8-wheel only Index 7 → Right wheel, Axle 4 (rear-right) Rule: always LEFT before RIGHT, front to rear. Even-indexed wheels (0, 2, 4, 6) are left. Odd-indexed (1, 3, 5, 7) are right. ═══════════════════════════════════════════════════════════════════════════════ STEERING SYSTEM — how each axle steers ═══════════════════════════════════════════════════════════════════════════════ ┌────────┬──────────────┬──────────────────────────────────────────────────┐ │ Axle │ Wheels │ Behavior │ ├────────┼──────────────┼──────────────────────────────────────────────────┤ │ Axle 1 │ [0] and [1] │ Full front steer (= wheelDir, always) │ │ Axle 2 │ [2] and [3] │ Same direction × steerAxle2Factor │ │ │ │ (0 = no steer, 1 = same as front) │ │ Axle 3 │ [4] and [5] │ Counter-steer × steerAxle3CounterMax │ │ │ │ fades to zero above steerRearFadeSpeed m/s │ │ Axle 4 │ [6] and [7] │ Counter-steer × steerAxle4CounterMax │ │ │ │ same speed fade as axle 3 │ └────────┴──────────────┴──────────────────────────────────────────────────┘ Rear steer fade formula: rearSteerBlend = 1 − clamp01(speed_m_s / steerRearFadeSpeed) At speed = 0 → blend = 1.0 (full rear steer, tight low-speed turns) At speed = fadeMax → blend = 0.0 (no rear steer, stable highway driving) ═══════════════════════════════════════════════════════════════════════════════ DIFFERENTIAL BIAS — how torque is split left/right ═══════════════════════════════════════════════════════════════════════════════ leftBias = 1 + diffBias × steerNorm rightBias = 1 − diffBias × steerNorm steerNorm is the normalized steering angle (−1 left … +1 right). When turning right (steerNorm > 0): Left wheel (outer on right turn) gets MORE torque. Right wheel (inner) gets LESS torque. This simulates a torque-sensitive differential that pushes the vehicle through the turn rather than fighting it. When diffLocked = ON (key pressed), bias = 0 → equal torque both sides. ═══════════════════════════════════════════════════════════════════════════════ -->