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[orx-marching-squares] Change findContours to return List<ShapeContour>

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This commit is contained in:
Edwin Jakobs
2023-02-02 22:03:51 +01:00
parent 9019e7e7ea
commit 5e6123c958
5 changed files with 65 additions and 18 deletions
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58
orx-marching-squares/src/commonMain/kotlin/MarchingSquares.kt
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@@ -4,17 +4,28 @@ import org.openrndr.math.IntVector2
import org.openrndr.math.Vector2
import org.openrndr.shape.LineSegment
import org.openrndr.shape.Rectangle
import org.openrndr.shape.ShapeContour
import kotlin.math.max
import kotlin.math.min
/**
* Find contours for a function [f] using the marching squares algorithm. A contour is found when f(x) crosses zero.
* @param f the function
* @param area a rectangular area in which the function should be evaluated
* @param cellSize the size of the cells, smaller size gives higher resolution
* @param useInterpolation intersection points will be interpolated if true, default true
* @return a list of [ShapeContour] instances
*/
fun findContours(
f: (Vector2) -> Double,
area: Rectangle,
cellSize: Double,
useInterpolation: Boolean = true
): List<LineSegment> {
): List<ShapeContour> {
val segments = mutableListOf<LineSegment>()
val values = mutableMapOf<IntVector2, Double>()
val segmentsMap = mutableMapOf<Vector2, MutableList<LineSegment>>()
for (y in 0 until (area.width / cellSize).toInt()) {
for (x in 0 until (area.width / cellSize).toInt()) {
@@ -25,9 +36,12 @@ fun findContours(
val zero = 0.0
for (y in 0 until (area.width / cellSize).toInt()) {
for (x in 0 until (area.width / cellSize).toInt()) {
val v00 = (values[IntVector2(x, y)] ?: zero)
val v10 = (values[IntVector2(x + 1, y)] ?: zero)
val v01 = (values[IntVector2(x, y + 1)] ?: zero)
// Here we check if we are at a right or top border. This is to ensure we create closed contours
// later on in the process.
val v00 = if (x == 0 || y == 0) zero else (values[IntVector2(x, y)] ?: zero)
val v10 = if (y == 0) zero else (values[IntVector2(x + 1, y)] ?: zero)
val v01 = if (x == 0) zero else (values[IntVector2(x, y + 1)] ?: zero)
val v11 = (values[IntVector2(x + 1, y + 1)] ?: zero)
val p00 = Vector2(x.toDouble(), y.toDouble()) * cellSize + area.corner
@@ -66,7 +80,12 @@ fun findContours(
) {
val r0 = blend(v00, v01)
val r1 = blend(v10, v11)
val l0 = LineSegment(p00.mix(p01, r0), p10.mix(p11, r1))
val v0 = p00.mix(p01, r0)
val v1 = p10.mix(p11, r1)
val l0 = LineSegment(v0, v1)
segmentsMap.getOrPut(v1) { mutableListOf() }.add(l0)
segmentsMap.getOrPut(v0) { mutableListOf() }.add(l0)
segments.add(l0)
}
@@ -103,5 +122,32 @@ fun findContours(
}
}
}
return segments
val processedSegments = mutableSetOf<LineSegment>()
val contours = mutableListOf<ShapeContour>()
for (segment in segments) {
if (segment in processedSegments) {
continue
} else {
val collected = mutableListOf<Vector2>()
var current: LineSegment? = segment
var closed = true
do {
current!!
collected.add(current.start)
processedSegments.add(current)
if (segmentsMap[current.start]!!.size < 2) {
closed = false
}
val hold = current
current = segmentsMap[current.start]?.firstOrNull { it !in processedSegments }
if (current == null) {
current = segmentsMap[hold.end]?.firstOrNull { it !in processedSegments }
}
} while (current != segment && current != null)
contours.add(ShapeContour.fromPoints(collected, closed = closed))
}
}
return contours
}