# Advanced Procedural Generation Parameters Guide

## Research-Based Parameter Tuning (2024)

This guide provides comprehensive parameter tuning for realistic procedural terrain generation based on latest research and industry best practices.

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## 1. Perlin Noise Parameters (Base Terrain)

### Core Parameters

**Octaves** (Number of noise layers)
- **Range:** 1-10
- **Low (1-3):** Smooth, rolling hills, gentle terrain
- **Medium (4-6):** Balanced detail, realistic mountains
- **High (7-10):** Extreme detail, rocky/jagged terrain
- **Recommended:** 6 for realistic terrain
- **Performance:** Each octave doubles computation time

**Persistence** (Amplitude multiplier per octave)
- **Range:** 0.0-1.0
- **Low (0.3-0.4):** Smooth terrain, gentle slopes
- **Medium (0.5-0.6):** Balanced, realistic terrain
- **High (0.7-0.9):** Rough, mountainous terrain
- **Recommended:** 0.5 for balanced terrain
- **Formula:** `amplitude *= persistence` per octave

**Lacunarity** (Frequency multiplier per octave)
- **Range:** 1.5-3.0
- **Low (1.5-1.8):** Gradual detail increase, smooth transitions
- **Medium (2.0-2.2):** Standard detail progression
- **High (2.5-3.0):** Rapid detail increase, sharp features
- **Recommended:** 2.0 for natural terrain
- **Formula:** `frequency *= lacunarity` per octave

**Scale** (Base frequency)
- **Range:** 10.0-500.0
- **Low (10-50):** Large features, continental scale
- **Medium (50-150):** Regional scale, valleys and mountains
- **High (150-500):** Local scale, small hills
- **Recommended:** 100.0 for balanced terrain
- **Effect:** Lower scale = larger features

**Amplitude** (Initial height multiplier)
- **Range:** 0.5-2.0
- **Low (0.5-0.8):** Subtle elevation changes
- **Medium (1.0-1.2):** Moderate elevation
- **High (1.5-2.0):** Extreme elevation differences
- **Recommended:** 1.0 for normalized output

### Advanced Noise Techniques

**Domain Warping** (Distortion for organic shapes)
- **Strength:** 0.0-50.0
  - 0-5: Subtle warping, slight organic feel
  - 5-20: Moderate warping, natural terrain
  - 20-50: Extreme warping, alien/fantasy terrain
- **Size:** 0.1-2.0
  - Small (0.1-0.5): Fine-grained distortion
  - Medium (0.5-1.0): Balanced distortion
  - Large (1.0-2.0): Large-scale warping
- **Formula:** `noise(x + strength * noise(size * x, size * y), y + strength * noise(size * x, size * y))`
- **Use Case:** Creates more organic, less grid-like terrain

**Ridged Noise** (Mountain ridges)
- **Formula:** `1.0 - abs(noise(x, y))`
- **Effect:** Creates sharp ridges and valleys
- **Use Case:** Mountain ranges, canyon systems

**Billowy Noise** (Cloud-like formations)
- **Formula:** `abs(noise(x, y))`
- **Effect:** Creates rounded, billowy shapes
- **Use Case:** Hills, dunes, cloud patterns

---

## 2. Hydraulic Erosion Parameters

### Research-Validated Settings (2024)

**Iterations**
- **Range:** 50-500
- **Fast (50-100):** Quick erosion, subtle effects
- **Balanced (100-200):** Realistic erosion, visible rivers
- **Detailed (200-500):** Deep valleys, complex drainage
- **Recommended:** 100 iterations (research: 10x faster with tuned constants)
- **Performance:** Linear scaling with iterations

**Rain Amount** (Water per droplet)
- **Range:** 0.5-2.0
- **Low (0.5-0.8):** Gentle erosion, subtle valleys
- **Medium (1.0-1.2):** Balanced erosion
- **High (1.5-2.0):** Aggressive erosion, deep canyons
- **Recommended:** 1.0

**Evaporation Rate**
- **Range:** 0.001-0.1
- **Low (0.001-0.005):** Water travels far, long rivers
- **Medium (0.01-0.03):** Balanced flow distance
- **High (0.05-0.1):** Short rivers, quick evaporation
- **Recommended:** 0.01 (research: 10x increase for faster convergence)
- **Effect:** Higher = faster convergence, fewer iterations needed

**Erosion Rate** (Terrain removal)
- **Range:** 0.1-0.5
- **Low (0.1-0.2):** Subtle erosion, gentle valleys
- **Medium (0.3-0.4):** Visible erosion, realistic valleys
- **High (0.4-0.5):** Aggressive erosion, deep canyons
- **Recommended:** 0.3
- **Balance:** Higher erosion = more dramatic terrain changes

**Deposition Rate** (Sediment placement)
- **Range:** 0.05-0.3
- **Low (0.05-0.1):** Minimal sediment buildup
- **Medium (0.1-0.2):** Balanced deposition
- **High (0.2-0.3):** Heavy sediment, alluvial fans
- **Recommended:** 0.1
- **Effect:** Creates sediment deposits at river mouths

**Min Slope** (Flow threshold)
- **Range:** 0.001-0.05
- **Low (0.001-0.005):** Water flows on flat terrain
- **Medium (0.01-0.02):** Balanced flow
- **High (0.03-0.05):** Water only flows on steep slopes
- **Recommended:** 0.01

**Gravity** (Flow acceleration)
- **Range:** 1.0-10.0
- **Low (1.0-3.0):** Slow water flow
- **Medium (4.0-6.0):** Realistic flow speed
- **High (7.0-10.0):** Fast, aggressive flow
- **Recommended:** 4.0

---

## 3. Thermal Erosion Parameters

### Talus Angle-Based Material Movement

**Iterations**
- **Range:** 20-100
- **Fast (20-30):** Subtle smoothing
- **Balanced (40-60):** Realistic slope stabilization
- **Detailed (70-100):** Smooth, stable slopes
- **Recommended:** 50 iterations

**Talus Angle** (Critical slope angle in radians)
- **Range:** 0.3-1.2 radians (17-69 degrees)
- **Low (0.3-0.5):** Very stable, gentle slopes (sand dunes)
- **Medium (0.6-0.8):** Realistic rock slopes (mountains)
- **High (0.9-1.2):** Steep cliffs, unstable terrain
- **Recommended:** 0.7 radians (~40 degrees)
- **Real-World:** Loose sand ~30°, rock ~35-45°, solid rock ~60-70°

**Material Transfer Rate**
- **Range:** 0.1-0.8
- **Low (0.1-0.3):** Slow material movement
- **Medium (0.4-0.6):** Balanced transfer
- **High (0.7-0.8):** Rapid material redistribution
- **Recommended:** 0.5

---

## 4. Climate Simulation Parameters

### Temperature Map

**Latitude Influence**
- **Range:** 0.0-1.0
- **Low (0.2-0.4):** Minimal temperature variation by latitude
- **Medium (0.5-0.7):** Realistic Earth-like gradient
- **High (0.8-1.0):** Extreme polar/equatorial difference
- **Recommended:** 0.6
- **Formula:** `temperature = 1.0 - (latitude * lat_influence + elevation * elev_influence)`

**Elevation Influence**
- **Range:** 0.0-1.0
- **Low (0.2-0.3):** Minimal cooling with altitude
- **Medium (0.4-0.5):** Realistic lapse rate (~6.5°C per 1000m)
- **High (0.6-0.8):** Extreme altitude cooling
- **Recommended:** 0.4
- **Real-World:** Temperature drops ~6.5°C per 1000m elevation

### Rainfall Map

**Water Proximity Influence**
- **Range:** 0.0-1.0
- **Low (0.2-0.3):** Minimal coastal rainfall boost
- **Medium (0.4-0.5):** Realistic coastal effect
- **High (0.6-0.8):** Strong maritime influence
- **Recommended:** 0.4

**Orographic Effect** (Mountain rainfall)
- **Range:** 0.0-1.0
- **Low (0.1-0.2):** Minimal rain shadow
- **Medium (0.3-0.4):** Realistic orographic precipitation
- **High (0.5-0.7):** Strong rain shadow effect
- **Recommended:** 0.3
- **Real-World:** Windward slopes get 2-10x more rain than leeward

**Base Rainfall**
- **Range:** 0.0-1.0
- **Arid (0.1-0.3):** Desert world
- **Moderate (0.4-0.6):** Earth-like
- **Wet (0.7-0.9):** Tropical world
- **Recommended:** 0.5

---

## 5. Biome Classification (Whittaker Diagram)

### Temperature Thresholds

**Tundra:** temp < 0.2 (cold)
**Taiga:** temp 0.2-0.4 (cool)
**Temperate:** temp 0.4-0.7 (moderate)
**Tropical:** temp > 0.7 (hot)

### Precipitation Thresholds

**Desert:** rain < 0.2 (arid)
**Grassland:** rain 0.2-0.5 (semi-arid)
**Forest:** rain 0.5-0.7 (humid)
**Rainforest:** rain > 0.7 (very humid)

### Elevation Overrides

**Alpine:** elevation > 0.7 (high altitude)
**Coastal:** distance_to_water < 10 cells
**Wetland:** elevation < 0.3 AND near water

### Biome Transition Smoothing

**Gaussian Blur Sigma**
- **Range:** 0.5-5.0
- **Sharp (0.5-1.0):** Distinct biome boundaries
- **Smooth (2.0-3.0):** Gradual transitions
- **Very Smooth (4.0-5.0):** Blended biomes
- **Recommended:** 2.0

---

## 6. Vegetation Distribution Parameters

### Density Calculation

**Formula:** `density = rainfall * (1 - abs(temperature - 0.5) * 2)`

**Factors:**
- **Rainfall:** Primary driver (more rain = more vegetation)
- **Temperature:** Optimal at moderate temps (0.5)
- **Elevation:** Reduces density at high altitudes
- **Slope:** Reduces density on steep slopes

**Density Thresholds:**
- **Sparse (0.0-0.3):** Desert, tundra, alpine
- **Moderate (0.3-0.6):** Grassland, savanna
- **Dense (0.6-0.8):** Temperate forest
- **Very Dense (0.8-1.0):** Tropical rainforest

### Tree Placement

**Spacing (based on density)**
- **Sparse:** 20-50m between trees
- **Moderate:** 10-20m between trees
- **Dense:** 5-10m between trees
- **Very Dense:** 2-5m between trees

**Size Variation**
- **Min Scale:** 0.7
- **Max Scale:** 1.3
- **Formula:** `scale = 0.7 + random() * 0.6`

---

## 7. River Network Parameters

### Flow Accumulation Threshold

**River Formation Threshold** (percentile of flow)
- **Sparse (90-93%):** Few major rivers
- **Moderate (93-95%):** Realistic river density
- **Dense (95-97%):** Many small streams
- **Very Dense (97-99%):** Creek networks
- **Recommended:** 95th percentile

**River Width** (based on flow accumulation)
- **Formula:** `width = sqrt(flow_accumulation) * scale_factor`
- **Scale Factor:** 0.1-0.5
  - Small (0.1-0.2): Narrow streams
  - Medium (0.2-0.3): Realistic rivers
  - Large (0.3-0.5): Wide rivers

**River Smoothing**
- **Gaussian Sigma:** 0.5-2.0
  - Low (0.5-1.0): Natural, meandering rivers
  - High (1.5-2.0): Smooth, artificial-looking rivers
- **Recommended:** 1.0

---

## 8. Preset Configurations

### Realistic Earth-Like Terrain
```python
{
    'octaves': 6,
    'persistence': 0.5,
    'lacunarity': 2.0,
    'scale': 100.0,
    'hydraulic_iterations': 100,
    'thermal_iterations': 50,
    'talus_angle': 0.7,
    'latitude_influence': 0.6,
    'elevation_influence': 0.4,
    'river_threshold': 95
}
```

### Mountainous Terrain
```python
{
    'octaves': 7,
    'persistence': 0.6,
    'lacunarity': 2.2,
    'scale': 80.0,
    'hydraulic_iterations': 150,
    'thermal_iterations': 60,
    'talus_angle': 0.8,
    'latitude_influence': 0.5,
    'elevation_influence': 0.5,
    'river_threshold': 96
}
```

### Rolling Hills
```python
{
    'octaves': 4,
    'persistence': 0.4,
    'lacunarity': 1.8,
    'scale': 150.0,
    'hydraulic_iterations': 80,
    'thermal_iterations': 40,
    'talus_angle': 0.6,
    'latitude_influence': 0.6,
    'elevation_influence': 0.3,
    'river_threshold': 94
}
```

### Desert World
```python
{
    'octaves': 5,
    'persistence': 0.45,
    'lacunarity': 2.0,
    'scale': 120.0,
    'hydraulic_iterations': 50,
    'thermal_iterations': 70,
    'talus_angle': 0.5,  # Sand dunes
    'latitude_influence': 0.7,
    'base_rainfall': 0.2,  # Arid
    'river_threshold': 97  # Few rivers
}
```

### Tropical Rainforest World
```python
{
    'octaves': 6,
    'persistence': 0.5,
    'lacunarity': 2.0,
    'scale': 100.0,
    'hydraulic_iterations': 120,
    'thermal_iterations': 40,
    'talus_angle': 0.7,
    'latitude_influence': 0.4,  # Warm everywhere
    'base_rainfall': 0.8,  # Very wet
    'river_threshold': 93  # Many rivers
}
```

### Alien/Fantasy Terrain
```python
{
    'octaves': 8,
    'persistence': 0.7,
    'lacunarity': 2.5,
    'scale': 60.0,
    'domain_warp_strength': 30.0,  # Extreme warping
    'hydraulic_iterations': 80,
    'thermal_iterations': 30,
    'talus_angle': 0.9,  # Steep cliffs
    'latitude_influence': 0.3,
    'river_threshold': 95
}
```

---

## 9. Performance vs Quality Trade-offs

### Fast Generation (Preview)
- Octaves: 4
- Hydraulic iterations: 50
- Thermal iterations: 20
- Resolution: 256x256
- **Time:** ~5 seconds

### Balanced (Production)
- Octaves: 6
- Hydraulic iterations: 100
- Thermal iterations: 50
- Resolution: 512x512
- **Time:** ~30 seconds

### High Quality (Hero Assets)
- Octaves: 8
- Hydraulic iterations: 200
- Thermal iterations: 80
- Resolution: 1024x1024
- **Time:** ~3 minutes

### Ultra Quality (Cinematic)
- Octaves: 10
- Hydraulic iterations: 500
- Thermal iterations: 100
- Resolution: 2048x2048
- **Time:** ~15 minutes

---

## 10. Common Issues & Solutions

### Issue: Terrain too smooth/boring
**Solution:** Increase octaves (6-8), increase persistence (0.6-0.7)

### Issue: Terrain too noisy/chaotic
**Solution:** Decrease octaves (4-5), decrease persistence (0.4-0.5)

### Issue: No visible rivers
**Solution:** Increase hydraulic iterations (150-200), lower river threshold (92-94%)

### Issue: Rivers too straight
**Solution:** Decrease river smoothing sigma (0.5-1.0), add domain warping

### Issue: Unrealistic biome distribution
**Solution:** Adjust temperature/rainfall influences, smooth biome transitions (sigma 2.0-3.0)

### Issue: Cliffs too steep/unstable
**Solution:** Increase thermal iterations (60-80), decrease talus angle (0.6-0.7)

### Issue: Terrain too flat
**Solution:** Increase amplitude (1.5-2.0), decrease scale (50-80)

### Issue: Generation too slow
**Solution:** Reduce resolution, decrease iterations, use fewer octaves

---

## 11. Research References

- **Hydraulic Erosion:** "Fast Hydraulic Erosion Simulation" (2024)
- **Thermal Erosion:** "Terrain Erosion on GPU" (Axel Paris, 2024)
- **Domain Warping:** Inigo Quilez (iquilezles.org)
- **Biome Classification:** Whittaker Diagram (1975), AutoBiomes (2020)
- **Perlin Noise:** Ken Perlin (1985), Improved Perlin Noise (2002)

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