The Most Efficient Way to Simulate Vehicle Suspension
In high-performance game development, simulating a vehicle isn't just about making it move; it’s about how the chassis interacts with the world. Whether you are building an arcade racer or a rugged off-road sim, choosing the right suspension model is critical for both CPU efficiency and player "feel."
1. The Raycast Suspension Model (The Industry Standard)
For 90% of games, from Halo to modern open-world titles, the Raycast-based suspension is the most efficient method. In this model, the wheels are not actual physics objects. Instead, they are represented by rays (or shape casts) fired downward from the chassis.
How it Works:
- Fire a raycast from each suspension mounting point toward the ground.
- Calculate the distance to the hit point to determine compression.
- Apply a Damped Spring Force to the chassis at that point based on Hooke’s Law: $F = kx + dv$.
Pros:
- Extremely Fast: Requires only 4–8 raycasts per frame.
- Stable: No "physics jitters" from complex joint constraints.
- Tunable: Easy to script arcade behaviors like mid-air leveling or artificial downforce.
2. Physics Constraints (The Realistic Approach)
Games like BeamNG.drive or heavy machinery simulators use Physics Constraints (Hinge joints, Sliders, and Springs). Here, the wheels are separate RigidBodies physically attached to the car body.
When to use it:
- When you need collision on the wheels themselves (e.g., a wheel getting caught on a rock edge).
- When visual accuracy of the suspension components (wishbones, struts) is the priority.
Cons:
- Performance Heavy: Solving multiple linked constraints is exponentially more expensive for the physics engine.
- Instability: High-speed collisions can cause the physics solver to "explode" if the mass ratios are not perfectly tuned.
3. Implementing the "Perfect" Spring Equation
To make a raycast suspension feel professional, you must implement a Damped Spring. Without damping, your car will bounce forever like a pogo stick. The formula for the force $F$ applied to the chassis is:
$$F = (stiffness \times compression) - (damping \times velocity)$$
- Compression: The difference between the max suspension length and the current raycast distance.
- Velocity: The speed at which the suspension is compressing or expanding (calculated by comparing the current length to the length in the previous frame).
4. Hybrid Optimization: The 2026 Meta
The most efficient professional setups in Godot 4.4, Unity, and Unreal 5.5 now use a Hybrid Shape-Cast approach. Instead of a single thin ray, they use a SphereCast or CylinderCast. This prevents the "needle" effect where a ray falls through a small crack in the geometry, providing a much smoother ride over rocky terrain without the cost of full constraint physics.
Summary Comparison Table
| Method | Efficiency | Realism | Best Use Case |
|---|---|---|---|
| Raycast | Highest | Medium | Arcade, Sim-Cade, Open World |
| Shape-Cast | High | High | Off-road, Rocky Terrain |
| Constraints | Low | Highest | Hardcore Simulators, Destruction |
Conclusion
If you want the best performance for your 2026 project, stick to the Raycast/Shape-cast model. It provides the most stability and gives you the "cleanest" data to feed into your tire friction and drifting logic. Save physics constraints only for cases where the mechanical parts of the car are the stars of the show.
