From be6d8f6d9af396d541f10e6ec035711b629f17e8 Mon Sep 17 00:00:00 2001
From: Adam Frisby
Date: Wed, 12 Mar 2008 13:49:38 +0000
Subject: * Switched Noise 'Flood Area' brush to use Perlin rather than random
 noise. * Fixed a bug with the Smooth Area brush.

---
 .../Modules/Terrain/FloodBrushes/NoiseArea.cs      | 63 +++++++++++++++++++++-
 1 file changed, 61 insertions(+), 2 deletions(-)

(limited to 'OpenSim/Region/Environment/Modules/Terrain/FloodBrushes/NoiseArea.cs')

diff --git a/OpenSim/Region/Environment/Modules/Terrain/FloodBrushes/NoiseArea.cs b/OpenSim/Region/Environment/Modules/Terrain/FloodBrushes/NoiseArea.cs
index d2433c3..6063b2f 100644
--- a/OpenSim/Region/Environment/Modules/Terrain/FloodBrushes/NoiseArea.cs
+++ b/OpenSim/Region/Environment/Modules/Terrain/FloodBrushes/NoiseArea.cs
@@ -31,6 +31,65 @@ namespace OpenSim.Region.Environment.Modules.Terrain.FloodBrushes
 {
     public class NoiseArea : ITerrainFloodEffect
     {
+        private double Noise(int x, int y)
+        {
+            // TODO: Seed
+            int n = x + y * 57;
+            n = (n<<13) ^ n;
+            return (1.0 - ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0);
+        }
+
+        private double SmoothedNoise1(int x, int y)
+        {
+            double corners = (Noise(x - 1, y - 1) + Noise(x + 1, y - 1) + Noise(x - 1, y + 1) + Noise(x + 1, y + 1)) / 16;
+            double sides = (Noise(x - 1, y) + Noise(x + 1, y) + Noise(x, y - 1) + Noise(x, y + 1)) / 8;
+            double center = Noise(x, y) / 4;
+            return corners + sides + center;
+        }
+
+        private double Interpolate(double x, double y, double z)
+        {
+            return (x * (1.0 - z)) + (y * z);
+        }
+
+        private double InterpolatedNoise(double x, double y)
+        {
+            int integer_X = (int)(x);
+            double fractional_X = x - integer_X;
+
+            int integer_Y = (int)y;
+            double fractional_Y = y - integer_Y;
+
+            double v1 = SmoothedNoise1(integer_X, integer_Y);
+            double v2 = SmoothedNoise1(integer_X + 1, integer_Y);
+            double v3 = SmoothedNoise1(integer_X, integer_Y + 1);
+            double v4 = SmoothedNoise1(integer_X + 1, integer_Y + 1);
+
+            double i1 = Interpolate(v1, v2, fractional_X);
+            double i2 = Interpolate(v3, v4, fractional_X);
+
+            return Interpolate(i1, i2, fractional_Y);
+        }
+
+        private double PerlinNoise2D(double x, double y)
+        {
+            int octaves = 1;
+            double persistence = 0.0005;
+
+            double frequency = 0.0;
+            double amplitude = 0.0;
+            double total = 0.0;
+
+            for (int i = 0; i < octaves; i++)
+            {
+                frequency = System.Math.Pow(2, i);
+                amplitude = System.Math.Pow(persistence, i);
+
+                total += InterpolatedNoise(x * frequency, y * frequency) * amplitude;
+            }
+            return total;
+        }
+
         #region ITerrainFloodEffect Members
 
         public void FloodEffect(ITerrainChannel map, bool[,] fillArea, double strength)
@@ -44,8 +103,8 @@ namespace OpenSim.Region.Environment.Modules.Terrain.FloodBrushes
                     {
                         lock (OpenSim.Framework.Util.RandomClass)
                         {
-                            double noise = OpenSim.Framework.Util.RandomClass.NextDouble();
-                            map[x, y] += (noise - 0.5) * strength;
+                            double noise = PerlinNoise2D(x, y);//OpenSim.Framework.Util.RandomClass.NextDouble();
+                            map[x, y] += (noise /*- 0.5*/) * strength;
                         }
                     }
                 }
-- 
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