added user settings to control river width variability and bank detail

main.go

@@ -158,7 +158,7 @@ func main() {
 		// Step 3: Generating Rivers
 		var riverImage image.Image
 
-		riverImage, riverPixels = GenerateRivers(settings.Width, settings.Height, settings.Rivers, settings.MinRiverWidth, settings.MaxRiverWidth, settings.RiverCurvyness, lakeImage, lakes, seedProvider.Next(), noiseImg)
+		riverImage, riverPixels = GenerateRivers(settings.Width, settings.Height, settings.Rivers, settings.MinRiverWidth, settings.MaxRiverWidth, settings.RiverCurvyness, lakeImage, lakes, seedProvider.Next(), noiseImg, settings.RiverWidthVariability, settings.RiverEdgeRoughness)
 
 		finalImage := riverImage.(*image.RGBA)
 
@@ -338,6 +338,31 @@ func main() {
 		val, _ := riverCurvynessSlider.value.Get()
 		settings.RiverCurvyness = val
 	}))
+
+	riverWidthVariabilitySlider := newNumericInputSlider(0, 100, settings.RiverWidthVariability, "%.0f%%", "River Width Variability")
+	riverWidthVariabilitySlider.entry.OnChanged = func(s string) {
+		riverWidthVariabilitySlider.validate(s, func(hasError bool) {
+			errorStates["riverWidthVariability"] = hasError
+			updateGenerateBtnState()
+		})
+	}
+	riverWidthVariabilitySlider.value.AddListener(binding.NewDataListener(func() {
+		val, _ := riverWidthVariabilitySlider.value.Get()
+		settings.RiverWidthVariability = val
+	}))
+
+	riverEdgeRoughnessSlider := newNumericInputSlider(0, 100, settings.RiverEdgeRoughness, "%.0f%%", "River Edge Roughness")
+	riverEdgeRoughnessSlider.entry.OnChanged = func(s string) {
+		riverEdgeRoughnessSlider.validate(s, func(hasError bool) {
+			errorStates["riverEdgeRoughness"] = hasError
+			updateGenerateBtnState()
+		})
+	}
+	riverEdgeRoughnessSlider.value.AddListener(binding.NewDataListener(func() {
+		val, _ := riverEdgeRoughnessSlider.value.Get()
+		settings.RiverEdgeRoughness = val
+	}))
+
 	minTreeSizeSlider := newNumericInputSlider(1, 150, settings.MinTreeSize, "%.0fpx", "Min Tree Size")
 	minTreeSizeSlider.entry.OnChanged = func(s string) {
 		minTreeSizeSlider.validate(s, func(hasError bool) {
@@ -516,7 +541,7 @@ func main() {
 				progressBar.SetValue(3.0 / 11.0)
 			})
 			var riverImage image.Image
-			riverImage, riverPixels = GenerateRivers(settings.Width, settings.Height, settings.Rivers, settings.MinRiverWidth, settings.MaxRiverWidth, settings.RiverCurvyness, lakeImage, lakes, seedProvider.Next(), noiseImg)
+			riverImage, riverPixels = GenerateRivers(settings.Width, settings.Height, settings.Rivers, settings.MinRiverWidth, settings.MaxRiverWidth, settings.RiverCurvyness, lakeImage, lakes, seedProvider.Next(), noiseImg, settings.RiverWidthVariability, settings.RiverEdgeRoughness)
 
 			finalImage := riverImage.(*image.RGBA)
 
@@ -682,6 +707,8 @@ func main() {
 		minRiverWidthSlider,
 		maxRiverWidthSlider,
 		riverCurvynessSlider,
+		riverWidthVariabilitySlider,
+		riverEdgeRoughnessSlider,
 	))
 
 	roadsTab := container.NewTabItem("Roads", container.NewVBox(

settings.go

@@ -23,6 +23,8 @@ type Settings struct {
 	MinRiverWidth         float64 `json:"min_river_width"`
 	MaxRiverWidth         float64 `json:"max_river_width"`
 	RiverCurvyness        float64 `json:"river_curvyness"`
+	RiverWidthVariability float64 `json:"river_width_variability"`
+	RiverEdgeRoughness    float64 `json:"river_edge_roughness"`
 
 	// Tree settings
 	MinTreeSize    float64 `json:"min_tree_size"`
@@ -122,6 +124,8 @@ func LoadSettings() (*Settings, error) {
 				MinRiverWidth:         1,
 				MaxRiverWidth:         5,
 				RiverCurvyness:        50,
+				RiverWidthVariability: 50,
+				RiverEdgeRoughness:    50,
 				NumRoads:              100,
 				MinRoadWidth:          2,
 				MaxRoadWidth:          8,

water.go

@@ -190,7 +190,7 @@ type River struct {
 }
 
 // GenerateRivers creates rivers on the map.
-func GenerateRivers(width, height, numRivers int, minWidth, maxWidth, curvyness float64, inputImage image.Image, lakes [][]image.Point, seed int64, heightmap image.Image) (image.Image, []image.Point) {
+func GenerateRivers(width, height, numRivers int, minWidth, maxWidth, curvyness float64, inputImage image.Image, lakes [][]image.Point, seed int64, heightmap image.Image, riverWidthVariability, riverEdgeRoughness float64) (image.Image, []image.Point) {
 	if numRivers == 0 {
 		return inputImage, nil
 	}
@@ -267,7 +267,7 @@ func GenerateRivers(width, height, numRivers int, minWidth, maxWidth, curvyness
 		radius := riverWidthPx / 2.0
 
 		for _, p := range path {
-			drawCircle(canvas, p, radius, color.RGBA{R: 0, G: 0, B: 255, A: 255}, &allRiverPixels, isWater, heightmap)
+			drawCircle(canvas, p, radius, color.RGBA{R: 0, G: 0, B: 255, A: 255}, &allRiverPixels, isWater, heightmap, riverWidthVariability, riverEdgeRoughness)
 		}
 		r.Points = path
 	}
@@ -410,14 +410,19 @@ func getPointOnEdge(width, height, edge int, randSrc *rand.Rand) image.Point {
 
 // drawCircle draws a circle on the image and adds its pixels to the given slice.
 // The outer edges are roughened using dual sin waves for natural-looking banks.
-func drawCircle(img *image.RGBA, center image.Point, radius float64, c color.Color, pixels *[]image.Point, isWater map[image.Point]bool, heightmap image.Image) {
+// riverWidthVariability controls the amplitude of width changes (0-100%).
+// riverEdgeRoughness controls the detail level of the edge roughness (0-100%).
+func drawCircle(img *image.RGBA, center image.Point, radius float64, c color.Color, pixels *[]image.Point, isWater map[image.Point]bool, heightmap image.Image, riverWidthVariability, riverEdgeRoughness float64) {
 	bounds := img.Bounds()
 
 	// Calculate dual sin wave amplitudes for outer edge roughening
-	// Large amplitude represents major variations in river width
+	// Large amplitude represents major variations in river width (controlled by riverWidthVariability)
-	// Small amplitude is 1/4 of large for subtle details
+	// At 0%, no width variation; at 100%, amplitude is 50% of radius
-	largeAmplitude := radius * 0.25
+	largeAmplitude := (radius * 0.5) * (riverWidthVariability / 100.0)
-	smallAmplitude := largeAmplitude / 4.0
+
+	// Small amplitude is controlled by riverEdgeRoughness
+	// At 0%, no detail; at 100%, detail amplitude equals large amplitude
+	smallAmplitude := largeAmplitude * (riverEdgeRoughness / 100.0)
 
 	for y := int(math.Floor(float64(center.Y) - radius)); y <= int(math.Ceil(float64(center.Y)+radius)); y++ {
 		for x := int(math.Floor(float64(center.X) - radius)); x <= int(math.Ceil(float64(center.X)+radius)); x++ {