Clifford Attractor Animation

main.go

// after running this program you can run
// ffmpeg -framerate 30 -i out/%06d.jpg -c:v libx264 -r 30 -pix_fmt yuv420p out2.mp4
package main

import (
	"fmt"
	"image"
	"image/color"
	"image/jpeg"
	"math"
	"os"
)

func makeFrame(a float64, b float64, c float64, d float64, i int) {
	width := 2000.0
	height := 2000.0
	img := image.NewRGBA(image.Rect(0, 0, int(width), int(height)))

	x := 0.0
	y := 0.0
	for i := 0; i < 1000000; i++ {
		x2 := math.Sin(a*y) + c*math.Cos(a*x)
		y2 := math.Sin(b*x) + d*math.Cos(b*y)
		x = x2
		y = y2
		img.Set(int(x*width/4+width/2), int(y*width/4+width/2), color.RGBA{0, 255, 0, 255})
	}

	f, _ := os.OpenFile(fmt.Sprintf("out/%06d.jpg", i), os.O_WRONLY|os.O_CREATE, 0600)
	defer f.Close()
	options := jpeg.Options{
		Quality: 95,
	}
	jpeg.Encode(f, img, &options)
}

func interpolate(n1 float64, n2 float64, i int, n int) float64 {
	return n1 + (n2-n1)/float64(n)*float64(i)
}

func main() {

	a1 := -1.4
	a2 := -1.2
	b1 := 1.6
	b2 := 1.9
	c1 := 1.0
	c2 := 1.4
	d1 := 0.7
	d2 := 0.9

	maxGoroutines := 8
	guard := make(chan struct{}, maxGoroutines)

	numFrames := 1000
	for i := 0; i < numFrames; i++ {
		guard <- struct{}{}
		go func(i int) {
			fmt.Println("Frame", i, "start")
			makeFrame(
				interpolate(a1, a2, i, numFrames),
				interpolate(b1, b2, i, numFrames),
				interpolate(c1, c2, i, numFrames),
				interpolate(d1, d2, i, numFrames),
				i,
			)
			fmt.Println("Frame", i, "done")
			<-guard
		}(i)
	}

}