From eddb3f9709a7ec95ce9762f2a0302fac29e6401e Mon Sep 17 00:00:00 2001
From: Yongwei Xing <yongwei.xing@liulishuo.com>
Date: Tue, 9 Mar 2021 13:41:11 +0800
Subject: [PATCH] add perlin noise

---
 common/perlinnoise.go          | 100 +++++++++++++++++++++++++++++++++
 contourline.go                 |  20 +++----
 example/example_contourline.go |  10 ++--
 3 files changed, 115 insertions(+), 15 deletions(-)
 create mode 100644 common/perlinnoise.go

diff --git a/common/perlinnoise.go b/common/perlinnoise.go
new file mode 100644
index 0000000..093244a
--- /dev/null
+++ b/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))
+}
diff --git a/contourline.go b/contourline.go
index 72a7e55..880df6f 100644
--- a/contourline.go
+++ b/contourline.go
@@ -11,7 +11,7 @@ type contourLine struct {
 	lineNum int
 }
 
-func NewContourLine(lineNum int) *contourLine{
+func NewContourLine(lineNum int) *contourLine {
 	return &contourLine{
 		lineNum: lineNum,
 	}
@@ -22,24 +22,24 @@ func (cl *contourLine) Generative(c *canva) {
 	ctex := gg.NewContextForRGBA(c.img)
 	noise := perlin.NewPerlin(2, 2, 3, rand.Int63())
 
-	for i:=0; i<cl.lineNum;i++ {
+	for i := 0; i < cl.lineNum; i++ {
 		cl := c.opts.colorSchema[rand.Intn(len(c.opts.colorSchema))]
 
-		for j :=0; j<5;j++ {
-			x := rand.Float64()*float64(c.width)
-			y := rand.Float64()*float64(c.height)
+		for j := 0; j < 5; j++ {
+			x := rand.Float64() * float64(c.width)
+			y := rand.Float64() * float64(c.height)
 
-			theta := noise.Noise2D(x/800.0, y/800.0) * math.Pi*2*800
-			x += math.Cos(theta)*0.4
-			y += math.Sin(theta)*0.4
+			theta := noise.Noise2D(x/800.0, y/800.0) * math.Pi * 2 * 800
+			x += math.Cos(theta) * 0.4
+			y += math.Sin(theta) * 0.4
 
 			ctex.SetColor(cl)
 			ctex.DrawEllipse(x, y, 1, 1)
 			ctex.Fill()
 
 			if x > float64(c.width) || x < 0 || y > float64(c.height) || y < 0 || rand.Float64() < 0.001 {
-				x = rand.Float64()*float64(c.width)
-				y = rand.Float64()*float64(c.height)
+				x = rand.Float64() * float64(c.width)
+				y = rand.Float64() * float64(c.height)
 			}
 		}
 	}
diff --git a/example/example_contourline.go b/example/example_contourline.go
index efd2a89..b472df7 100644
--- a/example/example_contourline.go
+++ b/example/example_contourline.go
@@ -10,11 +10,11 @@ import (
 func main() {
 	rand.Seed(time.Now().Unix())
 	colors := []color.RGBA{
-		{0x58, 0x18, 0x45, 0xFF },
-		{0x90, 0x0C, 0x3F, 0xFF },
-		{0xC7, 0x00, 0x39, 0xFF },
-		{0xFF, 0x57, 0x33, 0xFF },
-		{0xFF, 0xC3, 0x0F, 0xFF },
+		{0x58, 0x18, 0x45, 0xFF},
+		{0x90, 0x0C, 0x3F, 0xFF},
+		{0xC7, 0x00, 0x39, 0xFF},
+		{0xFF, 0x57, 0x33, 0xFF},
+		{0xFF, 0xC3, 0x0F, 0xFF},
 	}
 	c := generativeart.NewCanva(800, 800)
 	c.SetBackground(color.RGBA{0x1a, 0x06, 0x33, 0xFF})