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Don't recurse to size 2; only average corner of particular side you're on

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The former makes things so much faster. omg.
This commit is contained in:
Eryn Wells 2018-11-26 08:36:53 -08:00
parent 240499ced8
commit 1a32b8e085
2 changed files with 92 additions and 82 deletions
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66
Terrain2/Algorithms/DiamondSquare.swift
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@ -85,7 +85,7 @@ public class DiamondSquareGenerator: TerrainGenerator {
}
var subdivisions: [Box] {
guard size.w > 2 && size.h > 2 else {
guard size.w > 3 && size.h > 3 else {
return []
}
let halfSize = size.half
@ -159,16 +159,21 @@ public class DiamondSquareGenerator: TerrainGenerator {
heightMap[convert(pointToIndex: midpoint)] = midpointValue
// 2. Square step. For each of the side midpoints of this box, compute its value.
for pt in box.sideMidpoints {
let corners = diamondCorners(forPoint: pt, diamondSize: box.size)
let cornerValues = corners.map { (pt: Point) -> Float in
let idx = self.convert(pointToIndex: pt)
return heightMap[idx]
}
let ptValue = Float.random(in: spread) + self.average(ofPoints: cornerValues)
heightMap[convert(pointToIndex: pt)] = ptValue
func updateHeight(for p: Point, a: Point, b: Point) {
let aValue = heightMap[convert(pointToIndex: a)]
let bValue = heightMap[convert(pointToIndex: b)]
let avg = 0.5 * (aValue + bValue)
let rand = Float.random(in: spread)
let value = avg + rand
heightMap[convert(pointToIndex: p)] = value
}
updateHeight(for: box.north, a: box.northeast, b: box.northwest)
updateHeight(for: box.west, a: box.northwest, b: box.southwest)
updateHeight(for: box.south, a: box.southwest, b: box.southeast)
updateHeight(for: box.east, a: box.southeast, b: box.northeast)
if box.size != boxSize {
// Reduce the spread as we recurse down to smaller squares.
spread = -(spread.lowerBound * 0.5)...(spread.upperBound * 0.5)
@ -182,25 +187,30 @@ public class DiamondSquareGenerator: TerrainGenerator {
}
/// Find our diamond's corners, wrapping around the grid if needed.
func diamondCorners(forPoint pt: Point, diamondSize: Size) -> [Point] {
let halfSize = diamondSize.half
var corners = [Point(x: pt.x, y: pt.y - halfSize.h),
Point(x: pt.x - halfSize.w, y: pt.y),
Point(x: pt.x, y: pt.y + halfSize.h),
Point(x: pt.x + halfSize.w, y: pt.y)]
for i in 0..<corners.count {
if corners[i].x < 0 {
corners[i].x += grid.size.w - 1
} else if corners[i].x >= grid.size.w {
corners[i].x -= grid.size.w - 1
} else if corners[i].y < 0 {
corners[i].y += grid.size.h - 1
} else if corners[i].y >= grid.size.h {
corners[i].y -= grid.size.h - 1
}
}
return corners
}
// func diamondCorners(forPoint pt: Point, diamondSize: Size) -> [Point] {
// let halfSize = diamondSize.half
//
// func ptIsValid(pt: Point) -> Bool {
// return pt.x >= origin.x && pt.x < size.w && pt.y >= origin.y && pt.y < size.h
// }
//
// var corners = [Point(x: pt.x, y: pt.y - halfSize.h),
// Point(x: pt.x - halfSize.w, y: pt.y),
// Point(x: pt.x, y: pt.y + halfSize.h),
// Point(x: pt.x + halfSize.w, y: pt.y)].filter(ptIsValid)
// for i in 0..<corners.count {
// if corners[i].x < 0 {
// corners[i].x += grid.size.w - 1
// } else if corners[i].x >= grid.size.w {
// corners[i].x -= grid.size.w - 1
// } else if corners[i].y < 0 {
// corners[i].y += grid.size.h - 1
// } else if corners[i].y >= grid.size.h {
// corners[i].y -= grid.size.h - 1
// }
// }
// return corners
// }
func average(ofPoints pts: [Float]) -> Float {
let scale: Float = 1.0 / Float(pts.count)