add perlin noise

common/perlinnoise.go

@@ -0,0 +1,100 @@
+package common
+
+import (
+	"math"
+	"math/rand"
+)
+
+const (
+	perlinYwrapb     = 4
+	perlinYwrap      = 1 << perlinYwrapb
+	perlinZwrapb     = 8
+	perlinZwrap      = 1 << perlinZwrapb
+	perlinSize       = 4095
+	perlinOctaves    = 4
+	perlinAmpFalloff = 0.5
+)
+
+type perlinNoise struct {
+	perlin []float64
+}
+
+func NewPerlinNoise() *perlinNoise {
+	perlin := &perlinNoise{perlin: nil}
+	perlin.perlin = make([]float64, perlinSize+1)
+
+	for i, _ := range perlin.perlin {
+		perlin.perlin[i] = rand.Float64()
+	}
+	return perlin
+}
+
+func (p *perlinNoise) Noise(x, y, z float64) float64 {
+	if x < 0 {
+		x = -x
+	}
+
+	if y < 0 {
+		y = -y
+	}
+
+	if z < 0 {
+		z = -z
+	}
+
+	xi, yi, zi := int(math.Floor(x)), int(math.Floor(y)), int(math.Floor(z))
+	xf, yf, zf := x-float64(xi), y-float64(yi), z-float64(zi)
+
+	var rxf, ryf, n1, n2, n3 float64
+	var r float64
+	var ampl float64 = 0.5
+
+	for o := 0; o < perlinOctaves; o++ {
+		of := xi + (yi << perlinYwrapb) + (zi << perlinZwrapb)
+
+		rxf = scaledCosin(xf)
+		ryf = scaledCosin(yf)
+
+		n1 = p.perlin[of&perlinSize]
+		n1 += rxf * (p.perlin[(of+1)&perlinSize] - n1)
+		n2 = p.perlin[(of+perlinYwrap)&perlinSize]
+		n2 += rxf * (p.perlin[(of+perlinYwrap+1)&perlinSize] - n2)
+		n1 += ryf * (n2 - n1)
+
+		of += perlinZwrap
+		n2 = p.perlin[of&perlinSize]
+		n2 += rxf * (p.perlin[(of+1)&perlinSize] - n2)
+		n3 = p.perlin[(of+perlinYwrap)&perlinSize]
+		n3 += rxf * (p.perlin[(of+perlinYwrap+1)&perlinSize] - n3)
+		n2 += ryf * (n3 - n2)
+
+		n1 += scaledCosin(zf) * (n2 - n1)
+
+		r += n1 * ampl
+		ampl *= perlinAmpFalloff
+		xi <<= 1
+		xf *= 2
+		yi <<= 1
+		yf *= 2
+		zi <<= 1
+		zf *= 2
+
+		if xf >= 1.0 {
+			xi += 1
+			xf -= 1
+		}
+		if yf >= 1.0 {
+			yi += 1
+			yf -= 1
+		}
+		if zf >= 1.0 {
+			zi += 1
+			zf -= 1
+		}
+	}
+	return r
+}
+
+func scaledCosin(x float64) float64 {
+	return 0.5 * (1.0 - math.Cos(x*math.Pi))
+}