# Densify and generalize

A multipart geometry can be densified by adding interpolated points at regular intervals. Generalizing a multipart geometry simplifies it while preserving its general shape. Densifying a multipart geometry adds more vertices at regular intervals.

## Use case

The sample shows a polyline representing a ship's location at irregular intervals. The density of vertices along the ship's route is appropriate to represent the path of the ship at the sample map view's initial scale. However, that level of detail may be too great if you wanted to show a polyline of the ship's movement down the whole of the Willamette river. Then, you might consider generalizing the polyline to still faithfully represent the ship's passage on the river without having an overly complicated geometry.

Densifying a multipart geometry can be used to more accurately represent curved lines or to add more regularity to the vertices making up a multipart geometry.

## How to use the sample

Use the sliders to control the parameters of the densify and generalize methods. You can deselect the checkboxes for either method to remove its effect from the result polyline.

## How it works

1. Use the static method `GeometryEngine::densify(polyline, maxSegmentLength)` to densify the polyline object. The resulting polyline object will have more points along the line, so that there are no points greater than `maxSegmentLength` from the next point.
2. Use the static method `GeometryEngine::generalize(polyline, maxDeviation, true)` to generalize the polyline object. The resulting polyline object will have points shifted from the original line to simplify the shape. None of these points can deviate farther from the original line than `maxDeviation`. The last parameter, `removeDegenerateParts`, will clean up extraneous parts of a multipart geometry. This will have no effect in this sample as the polyline does not contain extraneous parts.
3. Note that `maxSegmentLength` and `maxDeviation` are in the units of the geometry's coordinate system. In this example, a cartesian coordinate system is used and at a small enough scale that geodesic distances are not required.

## Relevant API

• GeometryEngine
• Multipoint
• Point
• PointCollection
• Polyline
• SimpleLineSymbol
• SpatialReference

## Tags

densify, Edit and Manage Data, generalize, simplify

## Sample Code

DensifyAndGeneralize.cppDensifyAndGeneralize.cppDensifyAndGeneralize.hDensifyAndGeneralize.qml
Use dark colors for code blocksCopy
``````// [WriteFile Name=DensifyAndGeneralize, Category=Geometry]
// [Legal]

// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

// Unless required by applicable law or agreed to in writing, software
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "DensifyAndGeneralize.h"

#include "Map.h"
#include "MapQuickView.h"
#include "PointCollection.h"
#include "SpatialReference.h"
#include "Graphic.h"
#include "SimpleMarkerSymbol.h"
#include "SimpleLineSymbol.h"
#include "MultipointBuilder.h"
#include "PolylineBuilder.h"
#include "GeometryEngine.h"
#include "PointCollection.h"
#include "MapTypes.h"
#include "GraphicsOverlayListModel.h"
#include "GraphicListModel.h"
#include "SymbolTypes.h"
#include "ImmutablePartCollection.h"
#include "ImmutablePart.h"
#include "ImmutablePointCollection.h"
#include "GraphicsOverlay.h"
#include "Point.h"
#include "Polyline.h"
#include "Envelope.h"

#include <QFuture>

using namespace Esri::ArcGISRuntime;

DensifyAndGeneralize::DensifyAndGeneralize(QQuickItem* parent /* = nullptr */):
QQuickItem(parent)
{
}

void DensifyAndGeneralize::init()
{
// Register the map view for QML
qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
qmlRegisterType<DensifyAndGeneralize>("Esri.Samples", 1, 0, "DensifyAndGeneralizeSample");
}

void DensifyAndGeneralize::componentComplete()
{
QQuickItem::componentComplete();

// find QML MapView component
m_mapView = findChild<MapQuickView*>("mapView");

// Create a map using the streets night vector basemap
m_map = new Map(BasemapStyle::ArcGISStreetsNight, this);

m_graphicsOverlay = new GraphicsOverlay(this);
m_mapView->graphicsOverlays()->append(m_graphicsOverlay);

// Get Points along the river
PointCollection* pointCollection = createPointCollection();

// original multipart red graphic
MultipointBuilder multipointBuilder(pointCollection->spatialReference());
multipointBuilder.setPoints(pointCollection);
SimpleMarkerSymbol* originalSms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 7.0f /*size*/, this);
m_originalMultipointGraphic = new Graphic(multipointBuilder.toGeometry(), originalSms, this);
m_originalMultipointGraphic->setZIndex(0);
m_graphicsOverlay->graphics()->append(m_originalMultipointGraphic);

// original red dotted line graphic
PolylineBuilder polylineBuilder(pointCollection->spatialReference());
const int pointCollectionSize = pointCollection->size();
for (int i = 0; i < pointCollectionSize; i++)
{
}
SimpleLineSymbol* originalSls = new SimpleLineSymbol(SimpleLineSymbolStyle::Dot, QColor("red"), 3.0f /*size*/, this);
m_originalLineGraphic = new Graphic(polylineBuilder.toGeometry(), originalSls, this);
m_originalLineGraphic->setZIndex(1);
m_graphicsOverlay->graphics()->append(m_originalLineGraphic);

// resulting (densified and generalized) multipart magenta graphic
SimpleMarkerSymbol* resultSms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("magenta"), 7.0f /*size*/, this);
m_resultMultipointGraphic = new Graphic(this);
m_resultMultipointGraphic->setSymbol(resultSms);
m_resultMultipointGraphic->setZIndex(2);
m_graphicsOverlay->graphics()->append(m_resultMultipointGraphic);

// resulting (densified and generalized) multipart magenta graphic
SimpleLineSymbol* resultSls = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("magenta"), 3.0f /*size*/, this);
m_resultLineGraphic = new Graphic(this);
m_resultLineGraphic->setSymbol(resultSls);
m_resultLineGraphic->setZIndex(3);
m_graphicsOverlay->graphics()->append(m_resultLineGraphic);

// Set map to map view
m_mapView->setMap(m_map);

// set viewpoint
m_mapView->setViewpointGeometryAsync(m_originalMultipointGraphic->geometry().extent(), 100);
}

void DensifyAndGeneralize::updateGeometry(bool densify, double maxSegmentLength, bool generalize, double maxDeviation)
{
if (!m_originalLineGraphic)
return;

// Get the initial Geometry
Polyline polyline = geometry_cast<Polyline>(m_originalLineGraphic->geometry());
if (polyline.isEmpty())
return;

// Generalize the polyline
if (generalize)
polyline = geometry_cast<Polyline>(GeometryEngine::generalize(polyline, maxDeviation, true));

// Densify the polyline
if (densify)
polyline = geometry_cast<Polyline>(GeometryEngine::densify(polyline, maxSegmentLength));

// Update the line graphic
m_resultLineGraphic->setGeometry(polyline);

// Update the multipoint graphic
if (polyline.parts().size() < 1)
return;

MultipointBuilder multipointBuilder(polyline.spatialReference());
PointCollection* pointCollection = new PointCollection(polyline.spatialReference(), this);

ImmutablePointCollection polylinePoints = polyline.parts().part(0).points();
const int polylinePointsSize = polylinePoints.size();
for (int i = 0; i < polylinePointsSize; i++)
{
}
multipointBuilder.setPoints(pointCollection);
m_resultMultipointGraphic->setGeometry(multipointBuilder.toGeometry());
}

PointCollection* DensifyAndGeneralize::createPointCollection()
{
SpatialReference sr(32126);
PointCollection* pointCollection = new PointCollection(sr, this);