From ed9ecef80a8c6d834d9bf779fc6d53f2298bc2c5 Mon Sep 17 00:00:00 2001
From: Marc Di Luzio <marc.diluzio@gmail.com>
Date: Wed, 8 Jul 2020 20:10:28 +0100
Subject: [PATCH] Add perlin based generation for the terrain tiles

---
 go.mod                  |  1 +
 go.sum                  |  2 ++
 pkg/atlas/atlas.go      | 29 +++++++++++++++++++++++------
 pkg/atlas/atlas_test.go | 24 ++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/go.mod b/go.mod
index 2165ade..6c4320a 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/mdiluz/rove
 go 1.14
 
 require (
+	github.com/aquilax/go-perlin v0.0.0-20191229124216-0af9ce917c28
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/golang/protobuf v1.4.2
 	github.com/google/uuid v1.1.1
diff --git a/go.sum b/go.sum
index 029b75f..e579bf8 100644
--- a/go.sum
+++ b/go.sum
@@ -4,6 +4,8 @@ cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMT
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
+github.com/aquilax/go-perlin v0.0.0-20191229124216-0af9ce917c28 h1:iQUvYFmTKLXaDf3N0YfsJG5vgVtA1La82fHFDkpX5y4=
+github.com/aquilax/go-perlin v0.0.0-20191229124216-0af9ce917c28/go.mod h1:z9Rl7EM4BZY0Ikp2fEN1I5mKSOJ26HQpk0O2TBdN2HE=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f h1:WBZRG4aNOuI15bLRrCgN8fCq8E5Xuty6jGbmSNEvSsU=
diff --git a/pkg/atlas/atlas.go b/pkg/atlas/atlas.go
index 209d4b7..c6bcc37 100644
--- a/pkg/atlas/atlas.go
+++ b/pkg/atlas/atlas.go
@@ -4,6 +4,7 @@ import (
 	"log"
 	"math/rand"
 
+	"github.com/aquilax/go-perlin"
 	"github.com/mdiluz/rove/pkg/maths"
 	"github.com/mdiluz/rove/pkg/objects"
 	"github.com/mdiluz/rove/pkg/vector"
@@ -47,6 +48,9 @@ type Atlas struct {
 
 	// ChunkSize is the x/y dimensions of each square chunk
 	ChunkSize int `json:"chunksize"`
+
+	// perlin is the current perlin noise generator
+	perlin *perlin.Perlin
 }
 
 // NewAtlas creates a new empty atlas
@@ -57,6 +61,7 @@ func NewAtlas(chunkSize int) Atlas {
 		Chunks:     make([]Chunk, 1),
 		LowerBound: vector.Vector{X: 0, Y: 0},
 		UpperBound: vector.Vector{X: chunkSize, Y: chunkSize},
+		perlin:     perlin.NewPerlin(2, 2, 3, 100),
 	}
 	// Initialise the first chunk
 	a.populate(0)
@@ -102,12 +107,23 @@ func (a *Atlas) populate(chunk int) {
 	c.Tiles = make([]byte, a.ChunkSize*a.ChunkSize)
 	c.Objects = make(map[int]objects.Object)
 
-	// Set up the tiles
-	for i := 0; i < len(c.Tiles); i++ {
-		if rand.Intn(3) == 0 {
-			c.Tiles[i] = byte(TileRock)
-		} else {
-			c.Tiles[i] = byte(TileSand)
+	origin := a.chunkOriginInWorldSpace(chunk)
+	for i := 0; i < a.ChunkSize; i++ {
+		for j := 0; j < a.ChunkSize; j++ {
+
+			// Get the perlin noise value for this location
+			pl := a.perlin.Noise2D(float64(origin.X+i)/10, float64(origin.Y+j)/10)
+
+			// Choose a tile based on the perlin noise value
+			var tile Tile
+			switch {
+			case pl > 0.1:
+				tile = TileSand
+			default:
+				tile = TileRock
+			}
+
+			c.Tiles[j*a.ChunkSize+i] = byte(tile)
 		}
 	}
 
@@ -217,6 +233,7 @@ func (a *Atlas) worldSpaceToChunkWithGrow(v vector.Vector) int {
 		LowerBound: lower,
 		UpperBound: upper,
 		Chunks:     make([]Chunk, size.X*size.Y),
+		perlin:     a.perlin,
 	}
 
 	// Log that we're resizing
diff --git a/pkg/atlas/atlas_test.go b/pkg/atlas/atlas_test.go
index 60c3922..dedf4b1 100644
--- a/pkg/atlas/atlas_test.go
+++ b/pkg/atlas/atlas_test.go
@@ -1,6 +1,7 @@
 package atlas
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/mdiluz/rove/pkg/objects"
@@ -248,3 +249,26 @@ func TestAtlas_GetSetCorrect(t *testing.T) {
 		}
 	}
 }
+
+func TestAtlas_WorldGen(t *testing.T) {
+	a := NewAtlas(8)
+	// Spawn a large world
+	_, _ = a.QueryPosition(vector.Vector{X: 20, Y: 20})
+
+	// Print out the world for manual evaluation
+	num := 20
+	for j := num - 1; j >= 0; j-- {
+		for i := 0; i < num; i++ {
+			t, o := a.QueryPosition(vector.Vector{X: i, Y: j})
+			if o.Type != objects.None {
+				fmt.Printf("%c", o.Type)
+			} else if t != byte(TileNone) {
+				fmt.Printf("%c", t)
+			} else {
+				fmt.Printf(" ")
+			}
+
+		}
+		fmt.Print("\n")
+	}
+}