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metaverseDubai/docs/DAY_NIGHT_CYCLE.md

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Day/Night Cycle System - Dubai Metaverse

Overview

This document describes the day/night cycle system implementation for the Dubai Metaverse project.

System Architecture

BP_DayNightCycle Blueprint

Purpose: Central controller for time of day and lighting transitions

Components

  1. Time Variable: Float (0-24 hours)
  2. Sun Controller: Controls directional light rotation
  3. Sky Controller: Controls sky color and atmosphere
  4. Light Controller: Controls light intensity and color
  5. Event System: Triggers events at specific times

Time System

Time Format

  • Range: 0.0 - 24.0 (hours)
  • Precision: Float (allows smooth transitions)
  • Update: Real-time or accelerated time

Time Progression

  • Real-Time: 1:1 with real time (optional)
  • Accelerated: Faster time progression for demo
  • Manual Control: Manual time adjustment for testing

Time of Day Presets

Sunrise (6:00-8:00)

Duration: 2 hours

Lighting:

  • Sun Intensity: 4-6 lux (increasing)
  • Sun Color: Warm orange/red → white
  • Sky Color: Warm, dramatic → clear
  • Temperature: 4000K → 5500K

Atmosphere:

  • Fog Density: Medium
  • Fog Color: Warm orange
  • Volumetric: Enhanced

Post-Process:

  • Color Grading: Warm LUT
  • Bloom: Enhanced
  • Saturation: High

Daytime (8:00-17:00)

Duration: 9 hours

Lighting:

  • Sun Intensity: 8-12 lux (peak at noon)
  • Sun Color: White
  • Sky Color: Clear blue
  • Temperature: 6500K-7500K

Atmosphere:

  • Fog Density: Low
  • Fog Color: Neutral
  • Volumetric: Subtle

Post-Process:

  • Color Grading: Natural LUT
  • Bloom: Moderate
  • Saturation: Natural

Characteristics:

  • Harsh, direct sunlight
  • Strong shadows
  • High contrast
  • Clear visibility

Sunset (17:00-19:00)

Duration: 2 hours

Lighting:

  • Sun Intensity: 4-6 lux (decreasing)
  • Sun Color: White → warm orange/red
  • Sky Color: Clear → warm, dramatic
  • Temperature: 6500K → 4000K

Atmosphere:

  • Fog Density: Medium
  • Fog Color: Warm orange
  • Volumetric: Enhanced

Post-Process:

  • Color Grading: Warm LUT
  • Bloom: Enhanced
  • Saturation: High

Characteristics:

  • Warm, dramatic lighting
  • Long shadows
  • High contrast
  • Atmospheric

Night (19:00-6:00)

Duration: 11 hours

Lighting:

  • Sun Intensity: 0-1 lux (moonlight)
  • Sun Color: Cool blue
  • Sky Color: Dark, starry
  • Temperature: 8000K-10000K

Atmosphere:

  • Fog Density: Low
  • Fog Color: Cool blue/gray
  • Volumetric: Subtle

Post-Process:

  • Color Grading: Cool LUT
  • Bloom: Enhanced (neon lights)
  • Saturation: Reduced

Artificial Lighting:

  • Neon Signs: Bright, saturated colors
  • Street Lights: Warm, yellow
  • Building Lights: Interior lights visible
  • Marina Lights: Reflected in water

Characteristics:

  • Cool, atmospheric lighting
  • Soft shadows
  • Low contrast
  • Neon accents

Implementation

Blueprint Setup

  1. Create BP_DayNightCycle:

    • Create Blueprint class
    • Add time variable
    • Add event tick or timer

  2. Sun Rotation:

    • Calculate sun rotation based on time
    • Rotate directional light
    • Adjust sun intensity

  3. Sky Color:

    • Interpolate sky color based on time
    • Use curve or lerp
    • Update sky light

  4. Light Intensity:

    • Interpolate light intensity based on time
    • Use curve for smooth transitions
    • Update directional light

  5. Atmosphere:

    • Adjust fog density based on time
    • Adjust fog color based on time
    • Update exponential height fog

  6. Post-Process:

    • Switch LUTs based on time
    • Adjust post-process settings
    • Update post-process volume

Curves

Use Curves for Smooth Transitions:

  • Sun Intensity Curve: Float curve
  • Sun Color Curve: Vector curve (RGB)
  • Sky Color Curve: Vector curve (RGB)
  • Fog Density Curve: Float curve

Transitions

Smooth Transitions

Interpolation:

  • Use linear interpolation (lerp) for smooth transitions
  • Use curves for natural transitions
  • Update every frame or at intervals

Transition Duration:

  • Sunrise/Sunset: 2 hours (smooth transition)
  • Day/Night: Gradual transition
  • Avoid: Abrupt changes

Event Triggers

Events at Specific Times:

  • 6:00 AM: Sunrise start
  • 8:00 AM: Daytime start
  • 5:00 PM: Sunset start
  • 7:00 PM: Night start

Use Cases:

  • Trigger NPC behavior changes
  • Trigger audio changes
  • Trigger particle effects

Testing

Manual Testing

  1. Time Control:

    • Add manual time control (slider)
    • Test each time of day
    • Verify transitions

  2. Visual Validation:

    • Compare to reference photos
    • Verify lighting matches Dubai aesthetic
    • Check transitions are smooth

  3. Performance Testing:

    • Test performance at different times
    • Verify no performance issues
    • Optimize if needed

Automated Testing

  • Use scripts/lighting_validation.py to validate:
    • Time transitions
    • Light intensity values
    • Color values
    • Performance

Performance Considerations

Optimization

  1. Update Frequency:

    • Update every frame (smooth)
    • Or update at intervals (performance)

  2. Interpolation:

    • Use efficient interpolation
    • Cache values when possible

  3. Light Updates:

    • Batch light updates
    • Update only when needed

Dubai-Specific Considerations

Climate

  • Desert Climate: Hot, dry, clear skies
  • Sun Intensity: Very high during day
  • Heat Haze: Visible during day
  • Clear Nights: Clear, starry nights

Lighting Characteristics

  • Daytime: Harsh, direct sunlight
  • Sunset: Dramatic, warm colors
  • Night: Cool, clear with artificial lights
  • Reflections: Strong reflections from glass

Integration

With Other Systems

  1. NPCs: NPC behavior may change based on time
  2. Vehicles: Vehicle lights at night
  3. Audio: Ambient audio changes with time
  4. Particles: Particle effects (dust, heat haze) based on time

With Cinematics

  • Time Control: Set specific time for cinematic shots
  • Transitions: Use time transitions in cinematics
  • Consistency: Maintain time consistency across shots

Troubleshooting

Common Issues

Issue: Transitions not smooth

  • Solution: Use curves for interpolation
  • Solution: Increase update frequency

Issue: Lighting doesn't match reference

  • Solution: Adjust color values
  • Solution: Adjust intensity values

Issue: Performance issues

  • Solution: Reduce update frequency
  • Solution: Optimize interpolation

Documentation

Parameters

Document all exposed parameters:

  • Time variable
  • Sun rotation
  • Light intensity
  • Color values
  • Transition curves

Usage

Document how to use the system:

  • How to set time
  • How to adjust transitions
  • How to add new time presets

Version: 1.0 Last Updated: [Current Date]

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