Update temperature calculations

- Worlds were a bit cold, I've evened out the temperature across the
space for now (it probably needs more variance, but at least we're no
longer exclusively arctic wastelands ..)
- Removed vegetation map; seems like something a user can decide for
themselves

pkg/landscape/config.go

@@ -6,32 +6,25 @@ type Config struct {
 	// base map height
 	Height uint
 
-	Rain       *rainfallSettings
-	Vegetation *vegetationSettings
-	Temp       *tempSettings
-	Rivers     *riverSettings
-	Land       *landSettings
-	Sea        *seaSettings
+	Rain   *rainfallSettings
+	Temp   *tempSettings
+	Rivers *riverSettings
+	Land   *landSettings
+	Sea    *seaSettings
 }
 
 // tempSettings
 type tempSettings struct {
 	// in c, where 100 => 0c
 	EquatorAverageTemp uint8
 	PoleAverageTemp    uint8
+	EquatorWidth       float64
 }
 
 type rainfallSettings struct {
 	RainfallVariance float64
 }
 
-type vegetationSettings struct {
-	TempMin uint8
-	TempMax uint8
-	RainMin uint8
-	RainMax uint8
-}
-
 type riverSettings struct {
 	// number of rivers (max), we do not guarantee this many
 	Number uint
@@ -67,15 +60,10 @@ func DefaultConfig() *Config {
 		Rain: &rainfallSettings{
 			RainfallVariance: 0.03,
 		},
-		Vegetation: &vegetationSettings{
-			TempMin: 101,
-			TempMax: 150,
-			RainMin: 50,
-			RainMax: 255,
-		},
 		Temp: &tempSettings{
-			EquatorAverageTemp: 140, // 40c
-			PoleAverageTemp:    60,  // -40c
+			EquatorAverageTemp: 140,  // 40c
+			PoleAverageTemp:    60,   // -40c
+			EquatorWidth:       0.05, // % of height
 		},
 		Rivers: &riverSettings{
 			Number:                  1,

pkg/landscape/geography.go

@@ -11,33 +11,6 @@ func determineRainfall(hmap *MapImage, rs *rainfallSettings) *MapImage {
 	return &MapImage{im: perlin.Perlin(x, y, rs.RainfallVariance)}
 }
 
-// determineVegetation picks out where forests should be.
-// - not in sea
-// - not in rivers
-// - between certain temps
-// - between certain rainfall values
-func determineVegetation(sea, rvr, temp, rain *MapImage, vs *vegetationSettings) *MapImage {
-	x, y := sea.Dimensions()
-	vege := mutateImage(NewMapImage(x, y), func(dx, dy int, _ uint8) uint8 {
-		if sea.Value(dx, dy) == 255 || rvr.Value(dx, dy) == 255 {
-			return 0
-		}
-		rv := rain.Value(dx, dy)
-		tv := temp.Value(dx, dy)
-
-		if rv > vs.RainMin && rv < vs.RainMax && tv > vs.TempMin && tv < vs.TempMax {
-			// we're saying that rainfall is more important than
-			// temperature when determining vegetation
-			return toUint8((float64(rv) * 0.75) + (float64(tv) * 0.25))
-		}
-
-		return 0
-
-	})
-
-	return vege
-}
-
 // determineTemp returns a map of average temperatures in degrees Celcius,
 // where 100 => 0 degress (putting our min at -100c and max 155c .. seems
 // wide enough for an earth like planet)
@@ -58,27 +31,27 @@ func determineTemp(hm *MapImage, sealevel uint8, cfg *tempSettings) *MapImage {
 	_, y := hm.Dimensions()
 	equator := y / 2
 
+	// how wide the equator 'band' is
+	band := cfg.EquatorWidth * float64(y)
+
 	// difference in temp per pixel as we move out from the equator
-	dty := float64(cfg.EquatorAverageTemp-cfg.PoleAverageTemp) / float64(y/2)
+	dty := float64(cfg.EquatorAverageTemp-cfg.PoleAverageTemp) / ((float64(y) - band) / 2)
 
 	return mutateImage(hm, func(dx, dy int, z uint8) uint8 {
 		temp := cfg.EquatorAverageTemp
 
-		dueToZ := decrement(z, sealevel) / 2
-		if z < sealevel {
-			dueToZ = decrement(sealevel, z) / 2
-			dueToZ = increment(dueToZ, 10)
-		}
-
-		dueToY := float64(equator-dy) * dty
+		dueToY := 0.0
 		if dy > equator {
-			dueToY = float64(dy-equator) * dty
+			dueToY = float64(dy - equator)
+		} else {
+			dueToY = float64(equator - dy)
+		}
+		if dueToY <= band {
+			// we're inside the equator
+			return temp
 		}
 
-		temp = decrement(temp, dueToZ)
-		temp = decrement(temp, toUint8(dueToY))
-
-		return temp
+		return decrement(temp, toUint8(dueToY*dty))
 	})
 }
 

pkg/landscape/land.go

@@ -27,20 +27,13 @@ type Landscape struct {
 	// map of average rainfall .. unsure on exactly what this means ..
 	// but higher values imply more regular / more rain
 	rainfall *MapImage
-
-	// map of expected vegetation, where higher numbers indicated
-	// increasingly more lush vegetation.
-	// Values of 0 indicate barren desert, tundra, ice or similarly
-	// vegetation poor (or utterly lifeless) areas.
-	vegetation *MapImage
 }
 
 // Area represents a specific small area of the map
 type Area struct {
 	// 0-255, where higher is more/higher/better
 	Height      uint8
 	Rainfall    uint8
-	Vegetation  uint8
 	Temperature uint8 // in degress c, offset so 100 => 0 degrees cel
 
 	// if the square contains fresh/salt water
@@ -63,7 +56,6 @@ func (l *Landscape) At(x, y int) *Area {
 	return &Area{
 		Height:      l.height.Value(x, y),
 		Rainfall:    l.rainfall.Value(x, y),
-		Vegetation:  l.vegetation.Value(x, y),
 		Sea:         l.sea.Value(x, y) == 255,
 		River:       l.rivers.Value(x, y) == 255,
 		Temperature: l.temperature.Value(x, y),
@@ -84,7 +76,6 @@ func (w *Landscape) DebugRender() (string, error) {
 		{"rivers.png", w.rivers},
 		{"temperature.png", w.temperature},
 		{"rainfall.png", w.rainfall},
-		{"vegetation.png", w.vegetation},
 	} {
 		err := savePng(filepath.Join(d, i.Name), i.Img)
 		if err != nil {

pkg/landscape/perlinworld.go

@@ -45,14 +45,11 @@ func PerlinLandscape(cfg *Config) (*Landscape, error) {
 	}()
 	wg.Wait()
 
-	vege := determineVegetation(sea, rvrs, temp, rain, cfg.Vegetation)
-
 	return &Landscape{
 		height:      hmap,
 		sea:         sea,
 		rivers:      rvrs,
 		temperature: temp,
 		rainfall:    rain,
-		vegetation:  vege,
 	}, nil
 }