Create a convex hull for a given set of points. The convex hull is a polygon with shortest perimeter that encloses a set of points. As a visual analogy, consider a set of points as nails in a board. The convex hull of the points would be like a rubber band stretched around the outermost nails.
Use case
A convex hull can be useful in collision detection. For example, when charting the position of two yacht fleets (with each vessel represented by a point), if their convex hulls have been precomputed, it is efficient to first check if their convex hulls intersect before computing their proximity point-by-point.
How to use the sample
Tap on the map to add points. Click the "Convex hull" button to generate the convex hull of those points. Click the "Reset" button to start over.
How it works
Create an input geometry such as a Multipoint object.
Use GeometryEngine.convexHull(inputGeometry)to create a new Geometry object representing the convex hull of the input points. The returned geometry will either be a Point, Polyline, or Polygon based on the number of input points.
Relevant API
Geometry
GeometryEngine
Tags
convex hull, geometry, spatial analysis
Sample Code
ConvexHull.qml
Use dark colors for code blocksCopy
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
// [WriteFile Name=ConvexHull, Category=Geometry]// [Legal]// Copyright 2020 Esri.// Licensed under the Apache License, Version 2.0 (the "License");// you may not use this file except in compliance with the License.// You may obtain a copy of the License at// http://www.apache.org/licenses/LICENSE-2.0// Unless required by applicable law or agreed to in writing, software// distributed under the License is distributed on an "AS IS" BASIS,// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.// See the License for the specific language governing permissions and// limitations under the License.// [Legal]import QtQuick
import Esri.ArcGISRuntime
import QtQuick.Layouts
import QtQuick.Controls
Rectangle {
id: rootRectangleclip: truewidth: 800height: 600MapView {
id: mapViewanchors.fill: parentComponent.onCompleted: {
// Set the focus on MapView to initially enable keyboard navigation forceActiveFocus();
}
Map {
Basemap {
initStyle: Enums.BasemapStyleArcGISTopographic
}
}
GraphicsOverlay {
id: graphicsOverlayGraphic {
id: inputsGraphicSimpleMarkerSymbol {
id: markerSymbolstyle: Enums.SimpleMarkerSymbolStyleCircle
size: 10color: "red" }
}
Graphic {
id: convexHullGraphic }
}
SimpleFillSymbol {
id: fillSymbolstyle: Enums.SimpleFillSymbolStyleNull
color: "transparent"SimpleLineSymbol {
id: lineSymbolstyle: Enums.SimpleLineSymbolStyleSolid
width: 3color: "blue" }
}
MultipointBuilder {
id: multipointBuilderspatialReference: mapView.spatialReference
}
onMouseClicked: mouse => {
const clickedPoint = mapView.screenToLocation(mouse.x, mouse.y);
multipointBuilder.points.addPoint(clickedPoint);
inputsGraphic.geometry = multipointBuilder.geometry;
}
RowLayout {
anchors {
left: parent.left
top: parent.top
}
Button {
Layout.fillWidth: trueLayout.fillHeight: truetext: "Convex hull"// display the convex hullonClicked: {
// normalizing the geometry before performing geometric operationsconst normalizedPoints = GeometryEngine.normalizeCentralMeridian(multipointBuilder.geometry);
const convHull = GeometryEngine.convexHull(normalizedPoints);
if (convHull.geometryType === Enums.GeometryTypePoint) {
convexHullGraphic.symbol = markerSymbol;
} elseif (convHull.geometryType === Enums.GeometryTypePolyline) {
convexHullGraphic.symbol = lineSymbol;
} elseif (convHull.geometryType === Enums.GeometryTypePolygon) {
convexHullGraphic.symbol = fillSymbol;
}
else {
console.warn("Not a valid geometry");
}
convexHullGraphic.geometry = convHull;
}
}
Button {
Layout.fillWidth: trueLayout.fillHeight: truetext: "Reset"onClicked: {
multipointBuilder.points.removeAll();
inputsGraphic.geometry = null;
convexHullGraphic.geometry = null;
}
}
}
}
}