Optimizing Vehicle Physics For Indie Unity Games

Vehicle Physics Fundamentals for Indie Games

Rigidbodies, Colliders, and Forces

Rigidbodies and colliders are key components for implementing vehicle physics in Unity. Rigidbodies enable objects to receive forces and torques, while colliders define the shape and trigger collisions. indie developers should attach a rigidbody and appropriate collider shapes like box, wheel, or mesh colliders to vehicle parts. The mass and drag properties of rigidbodies greatly impact simulation quality. Denser, more massive materials like metal frames should have higher mass values. Materials causing more air resistance like front grilles can use higher drag. Applying downward force to grounded wheels via WheelColliders allows vehicles to accelerate realistically. Careful tuning of mass and physics materials is vital for responsive, grounded vehicle movement.

Wheel Colliders and Suspension Systems

The WheelCollider component manages tire friction, suspension distance, damping, and more to transmit forces from wheels to the rigidbody frame. Tweaking stiffness and compression settings in the wheel JointSpring can realistically simulate shock absorption when driving over uneven terrain. Suspension springs should be stiffer for performance vehicles and looser for offroad or utility designs enabling more wheel travel. The WheelFrictionCurve can also model slippery or sticky tire compounds for different road conditions like rain or dirt. Configuring appropriate suspension settings relative to vehicle weight and wheelbase is crucial for credible physics interactions.

Scripting Basic Vehicle Movement

indie developers can program basic vehicle controllers via Unity script components to apply torque and steering to the wheeled colliders. Simple starter scripts calculate speed based on accelerator input then apply a proportional torque to the rear wheels. Transforming the front wheels left/right via steering input will turn the vehicle at low to high speeds. More advanced control scripts could layer traction control, downshifting, or other assists atop the basic input-to-movement logic. Overall intuitive yet flexible vehicle behaviours arise from thoughtfully structured scripts, clean interfaces and focused single-responsibility classes. Savvy Unity programmers should architect their vehicle controllers for rapid iteration and experimentation.

Optimizing Performance of Vehicle Physics

Limiting Physics Calculations with Layers and Triggers

since vehicle physics are CPU-intensive, optimization is key for complex scenes. Unity???s layer-based collision matrix allows ignoring irrelevant collisions between vehicles, terrain, and other objects via the Physics settings window. Marking non-critical objects like trees, houses, etc as triggers also avoids wasted physics calcs. Disabling collision reporting and switching collisions to discrete rather than continuous modes further reduce overheads. Finally, pooling similar physics objects into layered containers judiciously contained by rough proxies streamlines calculations. Carefully limiting collisions through masking, triggers pooling accelerates physics to enable more vehicles and intricate handling.

Using Compound Colliders to Reduce Draw Calls

Constructing vehicles from many small primitive colliders stresses both CPU and GPU. Developer can optimize by grouping sets of cubes, spheres and capsules into larger Compound Colliders aligned to actual vehicle parts. Fewer separate colliders in scene hierarchy speeds up physics passes. Meanwhile batching discrete meshes into unified asset compounds도 decreases rendering cost by reducing draw calls due to fewer materials and sub-meshes. Performance profiler is invaluable for diagnosing mesh/collider optimization opportunities. Discerning use of compound colliders and meshes pays dividends for vehicle-intensive games.

Simplifying Mesh and Shape Collisions

Precise curvature-based collisions between complex vehicle meshes bog down mobile devices. Approximating curved surfaces via convex mesh decompositions or primitive shape colliders improves performance with minor accuracy tradeoff. Convex sub-meshes enable lighting and occlusion culling too compared to original concave models. Further, proxy robots replacing detailed interior assets also accelerates vehicle simulations. Finally, deforming mesh colliders to align with runtime wheel positions removes redundant collision checks. Mesh simplification, replacement and deformation judiciously applied heightens physics response for quality driving experiences.

Advanced Techniques for Realistic Vehicle Handling

Adding Sensor-Based Steering Assists

Believable steering feels interconnected to wheel grip, drift and orientation physics. Sophisticated modern power steering systems in real vehicles measure tire slip angles with torque and wheel speed sensors to seamlessly adjust assist levels. Emulating such systems, indie developers can script caster, camber and slip angle estimates using WheelCollider constituent values. Their custom power steering behaviours would then apply torques to align wheels under threshold slip values for grip or disable assists when intentional drifting. Plausible sensor-based steering logics enhance driving dynamics with lifelike weightiness.

Tuning Suspension and Tire Friction for Drifting

Game engines like Unity provide great wheel slip parameters for tuning drifty handling. Lower lateral friction values in the wheel JointSpring coupled with stiffer suspension springs allow inertia to overcome tire grip during cornering. To recover, dynamically restoring grip levels while countersteering enables slick transitions back to forward momentum. Further nuance comes from modulating handbrake input force for controlling slide duration and angle. Subtle braking and throttle tuning patiently balances the slide. Overall drift dynamics emerge not just from vehicle properties but environmental factors like road adhesion too. Savvy designers blend friction, suspension and input thresholds for flowing, finessed drift mechanics.

Applying Aerodynamic Downforce and Drag

As vehicle speed increases, inducing downforce via wings/spoilers presses tires downwards for tenacious cornering grip, while shaped underbodies generate suction on straightaways. Developers can simulate these via programmed torque vectors or wind zone components. But greater speed also increases drag which saps momentum over long stretches absent sufficient power. Here too physical materials on rigidbodies provide proxies for aerodynamic cost. Synthesizing weight, horsepower and aero factors fosters credible high-performance vehicle simulations. Test tracks with long straights and winding sections would prove downforce and drag settings. Augmenting physics with aerodynamics expands design possibilities.

Example Vehicle Controller Script

Reading Input and Calculating Speed/Direction

A sample vehicle controller script would first capture horizontal/vertical axes from input manager alongside acceleration, brake, and handbrake inputs. Then transformed vectors from an origin give speed along the vehicle???s forward axis for applying wheel torques or drag forces proportional to the accelerator value. The horizontal vector informs steering calculations while braking forces oppose forward velocity. Factor in mounted wing/spoiler torques for bonus downforce when moving above certain thresholds. Clear vector arithmetic makes for evolvable, extensible logic.

Applying Downforce and Rolling Resistance

Expanding our script, physical wing parts could raycast downward checking hit points to get relative speed and surface data for applying accurate downforces. Similarly, tire and wheel colliders provide rolling resistance values for each grounded contact patch to progressively bleed speed. Combined with engine power curves, fuel consumption rates, and traction factors, vehicles perform plausibly across varied conditions. Gradual refinement of physics vehicle scripts yields dividends in realistic feel.

Adding Collision Effects and Particle Effects

To heighten reactions, detecting collision events triggers rider animation swaying, camera shakes, audio crunches, and particles like dust puffs. Varying impulse magnitudes distort meshes and emit sparks, smoke, and fragments dynamically via code and object pooling. Elements reacting to physical impulses breathe life into vehicle interactions enhancing gameplay and aesthetics. Our controller handles movement while secondary effects systems manage gamefeel.