unity-weather-conditions

name	unity-weather-conditions
description	Unity Weather & Track Conditions for RC Racing

Unity Weather & Track Conditions for RC Racing

Use this skill when implementing dynamic weather systems and track condition modeling for an RC racing simulator. Covers weather state machines, global wetness, rain/dust/mud effects, wind physics, time of day, temperature models, track evolution, and wet surface shaders.

When to Use

• Implementing a weather state machine (clear, rain, drying transitions)
• Adding wet-track physics (grip reduction, aquaplaning, mud drag)
• Creating rain, dust, or mud particle effects
• Integrating wind forces with vehicle physics and particles
• Building time-of-day or temperature systems that affect racing
• Modeling track evolution (rubber buildup, marbles, oil spills)

When NOT to Use

• General particle system setup -- use unity-particles-vfx
• Shader authoring fundamentals -- use unity-shaders or unity-3d-materials
• Physics engine configuration (solver, timestep, layers) -- use unity-physics-tuning
• Networking weather state sync -- use unity-networking

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Global Wetness as Single Source of Truth

A single _GlobalWetness float (0 = bone dry, 1 = fully saturated) drives all weather-dependent systems.

// Set globally -- all shaders and scripts can read it
Shader.SetGlobalFloat("_GlobalWetness", currentWetness);

Consumers

System	How It Uses Wetness
Tire physics	grip *= (1f - wetness * surfaceConfig.wetGripReduction)
Shaders	Increase smoothness, darken albedo, enable ripple normals
Dust particles	emission = speed * (1f - wetness)
Rain particles	emission = wetness * maxRainParticles
Audio	Blend in rain ambience, tire splash sounds
AI	Reduce target speed, increase following distance

---

Wet Material Shaders

Shader Properties

// Add to existing surface shader or Shader Graph
float _GlobalWetness;   // Set via Shader.SetGlobalFloat
float _DirtAmount;      // Per-material

// Wetness effect:
// 1. Increase smoothness (wet surfaces are shinier)
float wetSmoothness = lerp(baseSmoothness, 0.95, _GlobalWetness);

// 2. Darken albedo (wet surfaces absorb more light)
float3 wetAlbedo = baseAlbedo * lerp(1.0, 0.6, _GlobalWetness);

// 3. Ripple normal map (animated water surface)
float2 rippleUV = worldPos.xz * 2.0 + _Time.y * float2(0.1, 0.15);
float3 rippleNormal = UnpackNormal(tex2D(_RippleNormalMap, rippleUV));
float3 finalNormal = lerp(baseNormal, rippleNormal, _GlobalWetness * 0.5);

---

Integration with SurfaceConfig

Extend existing surface configuration with wetness data:

[CreateAssetMenu(menuName = "Racing/Surface Config")]
public class SurfaceConfig : ScriptableObject
{
    [Header("Base Physics")]
    public float baseGrip;
    public float rollingResistance;

    [Header("Weather Modifiers")]
    [Range(0f, 1f)] public float wetGripReduction;     // How much grip drops when wet
    [Range(0f, 1f)] public float mudDragCoefficient;    // Drag in wet conditions
    public float dustEmissionRate;                       // Dust per unit speed
    public float waterAbsorptionRate;                    // How fast surface dries

    public float GetEffectiveGrip(float wetness)
    {
        return baseGrip * (1f - wetGripReduction * Mathf.Sqrt(wetness));
    }
}

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Implementation Priority

Priority	Feature	Effort	Impact
P1	Global wetness + grip reduction	Low	High -- core gameplay mechanic
P1	Weather state machine (Clear/Rain)	Medium	High -- drives all weather systems
P1	Rain particle system	Low	High -- essential visual feedback
P2	Wet surface shaders	Medium	Medium -- visual polish
P2	Dust system with moisture suppression	Low	Medium -- immersion
P2	Wind physics on vehicle	Low	Medium -- adds depth to racing
P3	Time of day lighting	Medium	Medium -- atmosphere
P3	Tire temperature model	Medium	Medium -- simulation depth
P3	Track evolution (rubber/marbles)	High	Medium -- advanced racing mechanic
P4	Mud dynamics with dirt accumulation	Medium	Low -- specific to off-road tracks
P4	Battery cold performance	Low	Low -- niche realism
P4	Dynamic quality adjustment	Medium	Low -- optimization polish

---

Related Skills

Skill	When to Use
unity-physics-3d	General physics foundations that grip/drag calculations build on
unity-physics-tuning	PhysX configuration for the vehicle that weather modifiers apply to
unity-particles-vfx	Particle system fundamentals for rain, dust, and mud effects
unity-3d-materials	Shader and material basics for wet surface rendering

Topic Pages

• Weather State Machine
• Rain System
• Performance Considerations