world.go

// Package genmap2derosion is based on "Simple Hydrology"
// See: https://nickmcd.me/2020/04/15/procedural-hydrology/
package genmap2derosion

import (
	"fmt"
	"image"
	"image/color"
	"math"
	"math/rand"

	"github.com/Flokey82/go_gens/vectors"
)

const worldsize = 256

type Params struct {
	StoreGIFFrames bool
	StorePNGCycles bool
	Height         int64
	Width          int64
	Seed           int64
	Size           vectors.IVec2
	UseWindErosion bool
}

var DefaultParams = &Params{
	StoreGIFFrames: true,
	StorePNGCycles: true,
	Seed:           DefaultSeed,
	Size: vectors.IVec2{
		X: worldsize,
		Y: worldsize,
	},
	UseWindErosion: false,
}

type World struct {
	r           *rand.Rand
	params      *Params
	images      []*image.Paletted // Generated frame used to construct the GIF.
	palette     []color.Color     // Default color palette.
	delays      []int             // Delay for each individual frame (0 for now).
	drainage    float64           // Drainage factor from pools
	scale       float64           // "Physical" Height scaling of the map
	heightmap   []float64         // Flat Array containing height information
	sediment    []float64         // Sediment storage (stores information on eroded / deposited sediment)
	windpath    []float64         // Wind Path Storage
	waterpath   []float64         // Water Path Storage (Rivers)
	waterpool   []float64         // Water Pool Storage (Lakes / Ponds)
	waterdrains []int             // Water Pool drainage points

	// Flux related information (experimental)
	fluxwaterpool []float64 // (TEMP Flux) Water Pool Storage (Lakes / Ponds)

	// Trees
	// trees []Plant
	// plantdensity [worldsize * worldsize]float64 //Density for Plants

	// Sediment erosion resistance
	// sedimentToughness [worldsize * worldsize]float64 // Sediment toughness storage
}

const DefaultSeed = 12356

func NewWorld(params *Params) *World {
	if params == nil {
		params = DefaultParams
	}

	idxSize := params.Size.X * params.Size.Y
	w := &World{
		params:        params,
		r:             rand.New(rand.NewSource(params.Seed)),
		drainage:      0.01,
		scale:         20.0,
		heightmap:     make([]float64, idxSize),
		sediment:      make([]float64, idxSize),
		windpath:      make([]float64, idxSize),
		waterpath:     make([]float64, idxSize),
		waterpool:     make([]float64, idxSize),
		waterdrains:   make([]int, idxSize),
		fluxwaterpool: make([]float64, idxSize),
	}

	// Prepare grayscale palette for GIF (0-255).
	for i := 0; i <= 255; i++ {
		w.palette = append(w.palette, color.RGBA{uint8(i), uint8(i), uint8(i), 0xff})
	}

	// Initialize all water drains to -1 (unset)
	for i := range w.waterdrains {
		w.waterdrains[i] = -1
	}

	// Generate basic heightmap.
	w.genTerrain()

	if w.params.UseWindErosion {
		// Deposit some loose sediment on the heightmap to get us started.
		for i, h := range w.heightmap {
			w.sediment[i] = h / 5
		}

		// Optionally just draw a pyramid instead of using the generated heightmap.
		drawPyramid := true
		if drawPyramid {
			// Note: Uncomment to place a huge pyramid in the middle
			var min, max float64
			for i := 0; i < int(w.params.Size.X*w.params.Size.Y); i++ {
				if w.heightmap[i] > max {
					max = w.heightmap[i]
				}
				if w.heightmap[i] < min {
					min = w.heightmap[i]
				}
			}

			for i := 0; i < int(w.params.Size.X*w.params.Size.Y); i++ {
				if w.heightmap[i] > 0.0 {
					w.heightmap[i] = 1.0
				} else {
					w.heightmap[i] = 0.0
				}
			}
			sinkPyramid := 0.3
			// Normalize
			for i := 0; i < int(w.params.Size.X*w.params.Size.Y); i++ {
				x := i / int(w.params.Size.Y)
				y := i % int(w.params.Size.Y)
				w.heightmap[i] = 1.2 - 2*(math.Abs(float64(x)-float64(w.params.Size.X)/2)/float64(w.params.Size.X)+math.Abs(float64(y)-float64(w.params.Size.Y)/2)/float64(w.params.Size.Y)) //0.9*(heightmap[i] - min)/(max - min);
				w.heightmap[i] -= sinkPyramid
				if w.heightmap[i] < 0.0 {
					w.heightmap[i] = 0.0
				}
				if w.heightmap[i] > w.sediment[i] {
					w.sediment[i] = 0.0
				} else {
					w.sediment[i] -= w.heightmap[i]
				}
			}
		}

		// Erode a few times.
		for i := 0; i < 400; i++ {
			w.erodeWind(250)
		}

		// Export heightmap and sediment.
		w.ExportPng("b_image.png", w.heightmap)
		w.ExportPng("b_image_sed.png", w.sediment)

		// Bake the heightmap (add the sediment)
		for i := 0; i < int(w.params.Size.X*w.params.Size.Y); i++ {
			w.heightmap[i] += w.sediment[i]
		}

		// Export combined heightmap and sediment.
		w.ExportPng("b_image_comb.png", w.heightmap)
	} else {
		// Generate climate.
		// w.genClimate()

		fmt.Println("generated")

		// Erode a few times.
		for j := 0; j < 5; j++ {
			w.doErosion(50, 600)
			// c := w.genClimate()
			// TODO: Update heightmap in climate struct.
			// w.erodeRain(1, c.AvgRainMap)

			// Export hydrology data generated by the original algorithm.
			if w.params.StorePNGCycles {
				w.ExportPng(fmt.Sprintf("b_image%d.png", j), w.heightmap)
				w.ExportPng(fmt.Sprintf("b_image%d_wp.png", j), w.waterpath)
				w.ExportPng(fmt.Sprintf("b_image%d_wpo.png", j), w.waterpool)
				w.ExportPng(fmt.Sprintf("b_image%d_sed.png", j), w.sediment)
				w.exportCombined(fmt.Sprintf("b_image%d_combo.png", j), w.heightmap, w.waterpath, w.waterpool)
			}

			// Optional stuff...

			// Call downhill, which will generate flux information.
			// for i, dhs := range w.getDownhill() {
			// 	if len(dhs) == 0 {
			// 		fmt.Println(fmt.Sprintf("sink: %d", i))
			// 	}
			// }

			// Export alternative hydrology data generated through flux.
			// w.export(fmt.Sprintf("b_image%d_flux_raw.png", j), w.getRawFlux())
			// w.export(fmt.Sprintf("b_image%d_flux.png", j), w.getFlux())
			// w.export(fmt.Sprintf("b_image%d_flux_wpo.png", j), w.fluxwaterpool[:])
		}

		// Bake the heightmap (add the sediment)
		for i := 0; i < int(w.params.Size.X*w.params.Size.Y); i++ {
			w.heightmap[i] += w.sediment[i]
		}
	}
	return w
}