Only detect exact collinear intersections in traces #6980
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,64 @@ | ||
| package org.odk.collect.shared.geometry.support | ||
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| import org.odk.collect.shared.geometry.LineSegment | ||
| import org.odk.collect.shared.geometry.Point | ||
| import org.odk.collect.shared.geometry.Trace | ||
| import org.odk.collect.shared.geometry.segments | ||
| import kotlin.random.Random | ||
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| object GeometryTestUtils { | ||
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| fun getTraceGenerator(maxLength: Int = 10, maxCoordinate: Double = 100.0): Sequence<Trace> { | ||
| return generateSequence { | ||
| val length = Random.nextInt(3, maxLength) | ||
| val trace = Trace(0.until(length).map { | ||
| Point( | ||
| Random.nextDouble(maxCoordinate * -1, maxCoordinate), | ||
| Random.nextDouble(maxCoordinate * -1, maxCoordinate) | ||
| ) | ||
| }) | ||
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| if (trace.isClosed()) { | ||
| trace | ||
| } else { | ||
| val shouldClose = Random.nextBoolean() | ||
| if (shouldClose) { | ||
| trace.copy(points = trace.points + trace.points.first()) | ||
| } else { | ||
| trace | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| fun Trace.reverse(): Trace { | ||
| return Trace(points.reversed()) | ||
| } | ||
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| fun Trace.scale(factor: Double): Trace { | ||
| return Trace(points.map { | ||
| Point(it.x * factor, it.y * factor) | ||
| }) | ||
| } | ||
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| fun Trace.addRandomIntersectingSegment(): Trace { | ||
| val intersectionSegment = segments().dropLast(1).random() | ||
|
Member
There was a problem hiding this comment. Why do we need to ignore the last segment? As I understand it, it avoids the scenario when the additional segment lies on the last segment but why? This still would be treated as an intersection.
Member
Author
There was a problem hiding this comment. Good question! I'd meant to add a comment when moving this to a method and then forgotten: This is basically the "two consecutive segments intersect" special case, and we test this it specifically ( |
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| val intersectPosition = Random.nextDouble(0.1, 1.0) | ||
| val intersectionPoint = intersectionSegment.interpolate(intersectPosition) | ||
| val lineSegment = LineSegment(points.last(), intersectionPoint) | ||
| val intersectingSegment = | ||
| LineSegment(lineSegment.start, lineSegment.interpolate(1.1)) | ||
|
Member
Author
There was a problem hiding this comment. Adding a line that intersects through another (rather than just touching) avoids needing to use an epsilon to account for the inaccurate |
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| return Trace(points + intersectingSegment.end) | ||
| } | ||
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| /** | ||
| * Calculate a [Point] on this [LineSegment] based on the `position` using | ||
| * [Linear interpolation](https://en.wikipedia.org/wiki/Linear_interpolation). `0` will return | ||
| * [LineSegment.start] and `1` will return [LineSegment.end]. | ||
| */ | ||
| fun LineSegment.interpolate(position: Double): Point { | ||
| val x = start.x + position * (end.x - start.x) | ||
| val y = start.y + position * (end.y - start.y) | ||
| return Point(x, y) | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| package org.odk.collect.shared.geometry.support | ||
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| import org.hamcrest.MatcherAssert.assertThat | ||
| import org.hamcrest.Matchers.equalTo | ||
| import org.junit.Test | ||
| import org.odk.collect.shared.geometry.LineSegment | ||
| import org.odk.collect.shared.geometry.Orientation | ||
| import org.odk.collect.shared.geometry.Point | ||
| import org.odk.collect.shared.geometry.orientation | ||
| import org.odk.collect.shared.geometry.support.GeometryTestUtils.interpolate | ||
| import org.odk.collect.shared.geometry.within | ||
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| class GeometryTestUtilsTest { | ||
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| @Test | ||
| fun `LineSegment#interpolate returns a point on the segment at a proportional distance`() { | ||
| val segment = LineSegment(Point(0.0, 0.0), Point(1.0, 0.0)) | ||
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| assertThat(segment.interpolate(0.0), equalTo(Point(0.0, 0.0))) | ||
| assertThat(segment.interpolate(0.5), equalTo(Point(0.5, 0.0))) | ||
| assertThat(segment.interpolate(1.0), equalTo(Point(1.0, 0.0))) | ||
| } | ||
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| @Test | ||
| fun `LineSegment#interpolate returns a collinear point within the line's bounding box`() { | ||
| val segment = LineSegment(Point(0.0, 0.0), Point(1.0, 1.0)) | ||
| val interpolatedPoint = segment.interpolate(0.5) | ||
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| val orientation = orientation(interpolatedPoint, segment.start, segment.end) | ||
| assertThat(orientation, equalTo(Orientation.Collinear)) | ||
| assertThat(interpolatedPoint.within(segment), equalTo(true)) | ||
| } | ||
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| @Test | ||
| fun `LineSegment#interpolate returns a collinear point within the line's bounding box for higher precision points with a suitable epsilon`() { | ||
| val segment = LineSegment(Point(56.6029153, 20.2311124), Point(56.6029192, 20.2310467)) | ||
| val interpolatedPoint = segment.interpolate(0.5) | ||
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| val orientation = orientation(interpolatedPoint, segment.start, segment.end, epsilon = 0.000001) | ||
| assertThat(orientation, equalTo(Orientation.Collinear)) | ||
| assertThat(interpolatedPoint.within(segment), equalTo(true)) | ||
| } | ||
| } |
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As mentioned in the PR description, I'm assuming we're going to end up tuning an epsilon for the
intersectsXPath function or allowing it to be tweaked so I've left this in.