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[orx-shapes] Add simple alphaShape interface

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This commit is contained in:
Edwin Jakobs
2021-11-20 23:53:01 +01:00
parent 085bca0106
commit 43b78954e5
1 changed files with 22 additions and 15 deletions
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37
orx-shapes/src/jvmMain/kotlin/AlphaShape.kt
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@@ -8,12 +8,19 @@ import kotlin.math.min
import kotlin.math.pow
import kotlin.math.sqrt
/**
* Create an alpha shape from list of [Vector2]
*/
fun List<Vector2>.alphaShape(): Shape {
return AlphaShape(this).createShape()
}
private fun circumradius(p1: Vector2, p2: Vector2, p3: Vector2): Double {
val a = (p2 - p1).length
val b = (p3 - p2).length
val c = (p1 - p3).length
return (a*b*c) / sqrt((a+b+c)*(b+c-a)*(c+a-b)*(a+b-c))
return (a * b * c) / sqrt((a + b + c) * (b + c - a) * (c + a - b) * (a + b - c))
}
/**
@@ -32,7 +39,7 @@ class AlphaShape(val points: List<Vector2>) {
val triangles = delaunay.triangles
var allEdges = mutableSetOf<Pair<Int, Int>>()
var perimeterEdges = mutableSetOf<Pair<Int, Int>>()
for (i in triangles.indices step 3){
for (i in triangles.indices step 3) {
val t0 = triangles[i] * 2
val t1 = triangles[i + 1] * 2
val t2 = triangles[i + 2] * 2
@@ -40,11 +47,11 @@ class AlphaShape(val points: List<Vector2>) {
val p2 = getVec(t1)
val p3 = getVec(t2)
val r = circumradius(p1, p2, p3)
if (r < alpha){
if (r < alpha) {
val edges = listOf(Pair(t0, t1), Pair(t1, t2), Pair(t2, t0))
for (edge in edges){
for (edge in edges) {
val fEdge = edge.flip()
if (edge !in allEdges && fEdge !in allEdges){
if (edge !in allEdges && fEdge !in allEdges) {
allEdges.add(edge)
perimeterEdges.add(edge)
} else {
@@ -96,8 +103,8 @@ class AlphaShape(val points: List<Vector2>) {
* As alpha goes to infinity, the alpha shape becomes equal to the convex hull of the input points.
* @return A list of [LineSegment]s representing the perimeter of the alpha shape.
*/
fun createSegments(alpha: Double): List<LineSegment>
= createBase(alpha).map { LineSegment(getVec(it.first), getVec(it.second)) }
fun createSegments(alpha: Double): List<LineSegment> =
createBase(alpha).map { LineSegment(getVec(it.first), getVec(it.second)) }
private fun getVec(i: Int) = Vector2(delaunay.points[i], delaunay.points[i + 1])
@@ -150,15 +157,15 @@ class AlphaShape(val points: List<Vector2>) {
// Find contour that encloses all other contours, if it exists
var enclosingContour = -1
for (i in contours.indices){
for (i in contours.indices) {
var encloses = true
for (j in contours.indices){
for (j in contours.indices) {
if (i == j) continue
if (contoursPoints[j].any { it !in contours[i] }){
if (contoursPoints[j].any { it !in contours[i] }) {
encloses = false
}
}
if (encloses){
if (encloses) {
enclosingContour = i
break
}
@@ -186,9 +193,9 @@ class AlphaShape(val points: List<Vector2>) {
var minY = Double.POSITIVE_INFINITY
var maxX = Double.NEGATIVE_INFINITY
var maxY = Double.NEGATIVE_INFINITY
for (i in delaunay.points.indices step 2){
for (i in delaunay.points.indices step 2) {
val x = delaunay.points[i]
val y = delaunay.points[i+1]
val y = delaunay.points[i + 1]
minX = min(minX, x)
maxX = max(maxX, x)
minY = min(minY, y)
@@ -200,8 +207,8 @@ class AlphaShape(val points: List<Vector2>) {
var upper = (maxX - minX).pow(2) + (maxY - minY).pow(2)
val precision = 0.001
while(lower < upper - precision){
val mid = (lower + upper)/2
while (lower < upper - precision) {
val mid = (lower + upper) / 2
if (decision(mid)) upper = mid else lower = mid
}