switch permutation generator to XORSHIFT

Author: tayloraswift

simplex.png

@@ -67,24 +67,23 @@ extension HashedNoise
     func table(seed:Int) -> ([Int], [Int])
     {
         let range:Int = Self.n_hashes
-        var seed = seed
-        var perm1024:[Int] = [Int](repeating: 0, count: 1024),
-            hashes:[Int]   = [Int](repeating: 0, count: 1024)
-        var source:[Int]   = Array(0 ..< 1024)
-        for i in stride(from: 1023, to: 0, by: -1)
+        var perm1024:[Int] = [Int](0 ..< 1024),
+            state128:(UInt32, UInt32, UInt32, UInt32) = (1, 0, 0, UInt32(extendingOrTruncating: seed))
+        for i in 0 ..< 1024 - 1
         {
-            seed = seed &* 6364136223846793005 &+ 1442695040888963407
-            var r:Int = (seed + 31) % (i + 1)
-            if r < 0
-            {
-                r += i + 1
-            }
-            perm1024[i] = source[r]
-            hashes[i]   = perm1024[i] % range
-            source[r]   = source[i]
+            var t:UInt32 = state128.3
+            t ^= t &<< 11
+            t ^= t &>> 8
+            state128.3 = state128.2
+            state128.2 = state128.1
+            state128.1 = state128.0
+            t ^= state128.0
+            t ^= state128.0 &>> 19
+            state128.0 = t
+            perm1024.swapAt(i, Int(t) & 1023)
         }
 
-        return (perm1024, hashes)
+        return (perm1024, perm1024.map{ $0 % range })
     }
 }
 

sources/noise/noise.swift

@@ -15,13 +15,13 @@ struct Simplex2D:Hashed2DGradientNoise
         hashes:[Int]
 
     private
-    let amplitude:Double,
+    let amplitude:Double, // this is not necissaryly the same amplitude passed into the initializer
         frequency:Double
 
     public
     init(amplitude:Double, frequency:Double, seed:Int = 0)
     {
-        self.amplitude = 7 * amplitude
+        self.amplitude = 0.096 * amplitude
         self.frequency = frequency
         (self.perm1024, self.hashes) = Simplex2D.table(seed: seed)
     }

sources/noise/opensimplex.swift

@@ -112,7 +112,7 @@ struct SuperSimplex2D:Hashed2DGradientNoise
     public
     init(amplitude:Double, frequency:Double, seed:Int = 0)
     {
-        self.amplitude = 1275 * amplitude
+        self.amplitude = 18 * amplitude
         self.frequency = frequency
         (self.perm1024, self.hashes) = SuperSimplex2D.table(seed: seed)
     }
@@ -366,7 +366,7 @@ struct SuperSimplex3D:Hashed3DGradientNoise
     public
     init(amplitude:Double, frequency:Double, seed:Int = 0)
     {
-        self.amplitude = 700 * amplitude
+        self.amplitude = 9 * amplitude
         self.frequency = frequency
         (self.perm1024, self.hashes) = SuperSimplex3D.table(seed: seed)
     }

sources/noise/supersimplex.swift

@@ -37,20 +37,20 @@ for point:PoissonSampler.Point in poisson.generate(radius: 10, width: viewer_siz
 print(clock() - t0)
 try png_encode(path: "poisson.png", raw_data: pixbuf, properties: png_properties)
 
-let S:fBm<Simplex2D> = fBm<Simplex2D>(amplitude: 1, frequency: 0.00083429273, octaves: 10)
+let S:fBm<Simplex2D> = fBm<Simplex2D>(amplitude: 0.5*127.5, frequency: 0.001, octaves: 10)
 t0 = clock()
 pixbuf = S.sample_area_saturated_to_u8(width: viewer_size, height: viewer_size, offset: 127.5)
 print(clock() - t0)
 try png_encode(path: "simplex.png", raw_data: pixbuf, properties: png_properties)
 
 
-let SS:fBm<SuperSimplex2D> = fBm<SuperSimplex2D>(amplitude: 1, frequency: 0.00083429273, octaves: 10)
+let SS:fBm<SuperSimplex2D> = fBm<SuperSimplex2D>(amplitude: 0.5*127.5, frequency: 0.001, octaves: 10)
 t0 = clock()
 pixbuf = SS.sample_area_saturated_to_u8(width: viewer_size, height: viewer_size, offset: 127.5)
 print(clock() - t0)
 try png_encode(path: "super_simplex.png", raw_data: pixbuf, properties: png_properties)
 
-let SS3D:fBm<SuperSimplex3D> = fBm<SuperSimplex3D>(amplitude: 1, frequency: 0.00083429273, octaves: 10)
+let SS3D:fBm<SuperSimplex3D> = fBm<SuperSimplex3D>(amplitude: 0.5*127.5, frequency: 0.001, octaves: 10)
 t0 = clock()
 pixbuf = SS3D.sample_area_saturated_to_u8(width: viewer_size, height: viewer_size, offset: 127.5)
 print(clock() - t0)