terrain.go

terrain.go

package main

import (
	"image"
	"image/png"
	"net/http"

	. "github.com/fogleman/pt/pt"
)

func LoadTile(url string) (image.Image, error) {
	resp, err := http.Get(url)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	return png.Decode(resp.Body)
}

func TerrariumToHeightMap(im image.Image) [][]float64 {
	w := im.Bounds().Size().X
	h := im.Bounds().Size().Y
	result := make([][]float64, h)
	data := make([]float64, w*h)
	for i := range result {
		result[i], data = data[:w], data[w:]
	}
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			red, green, blue, _ := im.At(x, y).RGBA()
			r := float64(red) / 256
			g := float64(green) / 256
			b := float64(blue) / 256
			h := (r*256 + g + b/256) - 32768
			result[y][x] = h * 0.05
		}
	}
	return result
}

func HeightMapToMesh(data [][]float64) *Mesh {
	const n = 1
	h := len(data)
	w := len(data[0])
	material := GlossyMaterial(HexColor(0x334D5C), 1.1, Radians(30))
	material.Texture = GetTexture("../density/texture.png", 2.2)
	var triangles []*Triangle
	for y := 0; y < h-n; y += n {
		for x := 0; x < w-n; x += n {
			v00 := Vector{float64(x) + 0, float64(y) + 0, data[y+0][x+0]}
			v01 := Vector{float64(x) + 0, float64(y) + n, data[y+n][x+0]}
			v10 := Vector{float64(x) + n, float64(y) + 0, data[y+0][x+n]}
			v11 := Vector{float64(x) + n, float64(y) + n, data[y+n][x+n]}
			t00 := Vector{float64(x+0) / float64(w), 1 - float64(y+0)/float64(h), 0}
			t01 := Vector{float64(x+0) / float64(w), 1 - float64(y+n)/float64(h), 0}
			t10 := Vector{float64(x+n) / float64(w), 1 - float64(y+0)/float64(h), 0}
			t11 := Vector{float64(x+n) / float64(w), 1 - float64(y+n)/float64(h), 0}
			triangles = append(triangles, NewTriangle(v00, v10, v11, t00, t10, t11, material))
			triangles = append(triangles, NewTriangle(v00, v11, v01, t00, t11, t01, material))
		}
	}
	return NewMesh(triangles)
}

func main() {
	im, err := LoadPNG("../density/out.png")
	// im, err := LoadTile("https://terrain-preview.mapzen.com/terrarium/9/91/186.png")
	if err != nil {
		panic(err)
	}
	mesh := HeightMapToMesh(TerrariumToHeightMap(im))
	mesh.FitInside(Box{V(-1, -1, 0), V(1, 1, 1)}, V(0.5, 0.5, 0))
	// mesh.SmoothNormals()

	scene := Scene{}
	// scene.SetColor(Color{1, 1, 1})
	scene.Add(mesh)
	light := LightMaterial(Color{1, 1, 1}, 1, NoAttenuation)
	scene.Add(NewSphere(V(0, -1, 2), 1, light))
	camera := LookAt(Vector{-1, 1, 0.5}, Vector{0, 0, -0.5}, Vector{0, 0, 1}, 35)
	IterativeRender("out%03d.png", 1000, &scene, &camera, 2560/2, 1440/2, -1, 4, 4)
}

hi, what is the "../density/texture.png"?
i have tried texture under pt/examples folder, results are all black.