Example using 3D Simplex noise

tilegen3d.go

// Copyright 2012 by Sascha L. Teichmann. All rights reserved.
//
// Simple example how to use 3D Simplex noise.
// $ go get bitbucket.org/s_l_teichmann/simplexnoise
// $ go build tilegen3d.go
//
package main

import (
	"bitbucket.org/s_l_teichmann/simplexnoise"
	"bufio"
	"flag"
	"fmt"
	"log"
	"os"
)

func main() {
	var (
		seed   int64
		size   int
		xofs   int
		yofs   int
		zofs   int
		step   float64
		pt     float64
		pb     float64
		thresh float64
		output string
	)

	flag.Int64Var(&seed, "seed", 1, "random seed")
	flag.IntVar(&size, "size", 64, "tile size")
	flag.IntVar(&xofs, "xofs", 0, "xofs")
	flag.IntVar(&yofs, "yofs", 0, "yofs")
	flag.IntVar(&zofs, "zofs", 0, "yofs")
	flag.Float64Var(&pt, "pt", 1.0, "probalility top")
	flag.Float64Var(&pb, "pb", 1.0, "probalility bottom")
	flag.Float64Var(&thresh, "thresh", 1.0, "threshhold")
	flag.Float64Var(&step, "step", 1.0/256.0, "step")
	flag.StringVar(&output, "output", "", "file to store the tile")

	flag.Parse()

	sn := simplexnoise.NewSimplexNoise(seed)

	x_start := float64(xofs*size) * step
	y_start := float64(yofs*size) * step
	z_start := float64(zofs*size) * step

	// pt = 0*m + b <=> b = pt
	// pb = (size-1)*m + pt
	// m = (pb-pt)/(size-1)

	b := float64(pt)
	var m float64
	if size == 1 {
		m = 0
	} else {
		m = float64(pb-pt) / float64(size-1)
	}

	if output == "" {
		output = fmt.Sprintf("%d-%d-%d.raw", xofs, yofs, zofs)
	}

	file, err := os.Create(output)
	if err != nil {
		log.Printf("Cannot open '%s'", output)
		os.Exit(1)
	}
	defer file.Close()

	buf := bufio.NewWriter(file)

	z_pos := z_start
	for z := 0; z < size; z++ {
		y_pos := y_start
		for y := 0; y < size; y++ {
			yp := m*float64(y) + b
			x_pos := x_start
			for x := 0; x < size; x++ {
				n := (sn.Noise3D(x_pos, y_pos, z_pos) + 1.0) * 0.5 * yp
				if n < thresh {
					n = 0.0
				}
				if err := buf.WriteByte(byte(n * 255.0)); err != nil {
					log.Printf("Write to '%s' failed", output)
					os.Exit(1)
				}
				x_pos += step
			}
			y_pos += step
		}
		z_pos += step
	}
	buf.Flush()
}