Viewshed (location)

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C++

QML

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Sample viewer app

Perform a viewshed analysis from a defined vantage point.

screenshot

Use case

A 3D viewshed analysis is a type of visual analysis you can perform on a scene. The viewshed shows what can be seen from a given location. The output is an overlay with two different colors - one representing the visible areas (green) and the other representing the obstructed areas (red). Viewshed analysis is a form of "exploratory analysis", which means the results are calculated on the current scale of the data, and the results are generated very quickly. If more "conclusive" results are required, consider using a GeoprocessingTask to perform a viewshed instead.

How to use the sample

Use the sliders to change the properties (heading, pitch, etc.), of the viewshed and see them updated in real time. To move the viewshed, double touch and drag your finger across the screen. Lift your finger to stop moving the viewshed.

How it works

Create a LocationViewshed passing in the observer location, heading, pitch, horizontal/vertical angles, and min/max distances.
Set the property values on the viewshed instance for location, direction, range, and visibility properties.

Relevant API

AnalysisOverlay
ArcGISSceneLayer
ArcGISTiledElevationSource
LocationViewshed
Viewshed

About the data

The scene shows a buildings layer in Brest, France hosted on ArcGIS Online.

Sample Code

ViewshedLocation.cpp

ViewshedLocation.h

ColorDialog.qml

ViewshedSlider.qml

ViewshedLocation.qml

Use dark colors for code blocksCopy
// [WriteFile Name=ViewshedLocation, Category=Analysis]
// [Legal]
// Copyright 2017 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]

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

#include "ViewshedLocation.h"

#include "ArcGISTiledElevationSource.h"
#include "Scene.h"
#include "SceneQuickView.h"
#include "LocationViewshed.h"
#include "Camera.h"
#include "Point.h"
#include "AnalysisOverlay.h"


using namespace Esri::ArcGISRuntime;

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

void ViewshedLocation::init()
{
  // Register classes for QML
  qmlRegisterType<SceneQuickView>("Esri.Samples", 1, 0, "SceneView");
  qmlRegisterType<ViewshedLocation>("Esri.Samples", 1, 0, "ViewshedLocationSample");
}

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

  // Create a scene and give it to the SceneView
  m_sceneView = findChild<SceneQuickView*>("sceneView");

  Scene* scene = new Scene(BasemapStyle::ArcGISTopographic, this);
  Surface* surface = new Surface(this);
  surface->elevationSources()->append(
        new ArcGISTiledElevationSource(
          QUrl("https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"),
          this));
  scene->setBaseSurface(surface);
  m_sceneView->setArcGISScene(scene);

  // Add an Analysis Overlay
  m_analysisOverlay = new AnalysisOverlay(this);
  m_sceneView->analysisOverlays()->append(m_analysisOverlay);

  // set initial viewpoint
  setInitialViewpoint();

  // connect signals
  connectSignals();
}

void ViewshedLocation::setInitialViewpoint()
{
  // Set a viewpoint
  double x = 6.86088;
  double y = 45.3604;
  double z = 3582.55;
  Point point(x, y, z, SpatialReference(4326));
  double heading = 345;
  double pitch = 70;
  double roll = 0;
  Camera camera(point, heading, pitch, roll);
  m_sceneView->setViewpointCamera(camera);
}

void ViewshedLocation::connectSignals()
{
  // on mouse click perform the location viewshed
  connect(m_sceneView, &SceneQuickView::mouseClicked, this, [this](QMouseEvent& event)
  {
    if (!m_locationViewshed)
      createViewshed(event.x(), event.y());
    else
    {
      const Point pt = m_sceneView->screenToBaseSurface(event.x(), event.y());
      m_locationViewshed->setLocation(pt);
    }
  });

  connect(m_sceneView, &SceneQuickView::mousePressedAndHeld, this, [this](QMouseEvent& event)
  {
    if (!m_locationViewshed)
      createViewshed(event.x(), event.y());

    m_calculating = true;
  });

  connect(m_sceneView, &SceneQuickView::mouseMoved, this, [this](QMouseEvent& event)
  {
    if (m_calculating)
    {
      const Point pt = m_sceneView->screenToBaseSurface(event.x(), event.y());
      m_locationViewshed->setLocation(pt);
    }
  });

  connect(m_sceneView, &SceneQuickView::mouseReleased, this, [this]
  {
    m_calculating = false;
  });
}

void ViewshedLocation::createViewshed(double x, double y)
{
  const Point pt = m_sceneView->screenToBaseSurface(x, y);

  // Create the Location Viewshed
  m_locationViewshed = new LocationViewshed(pt, m_heading, m_pitch,
                                            m_horizontalAngle, m_veriticalAngle,
                                            m_minDistance, m_maxDistance, this);
  m_locationViewshed->setVisible(m_viewshedVisible);

  // Add the Viewshed to the Analysis Overlay
  m_analysisOverlay->analyses()->append(m_locationViewshed);

  return;
}

// Getters/Setters for each Q_PROPERTY
bool ViewshedLocation::isViewshedVisible() const
{
  return m_viewshedVisible;
}

void ViewshedLocation::setViewshedVisible(bool viewshedVisible)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->isVisible() == viewshedVisible)
      return;

    m_viewshedVisible = viewshedVisible;
    m_locationViewshed->setVisible(viewshedVisible);
  }
  else
  {
    if (m_viewshedVisible == viewshedVisible)
      return;

    m_viewshedVisible = viewshedVisible;
  }

  emit viewshedVisibleChanged();
}

bool ViewshedLocation::isFrustumOutlineVisible() const
{
  return m_locationViewshed ? m_locationViewshed->isFrustumOutlineVisible() : m_frustumVisible;
}

void ViewshedLocation::setFrustumOutlineVisible(bool frustumVisible)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->isFrustumOutlineVisible() == frustumVisible)
      return;

    m_frustumVisible = frustumVisible;
    m_locationViewshed->setFrustumOutlineVisible(frustumVisible);
  }
  else
  {
    if (m_frustumVisible == frustumVisible)
      return;

    m_frustumVisible = frustumVisible;
  }

  emit frustumVisibleChanged();
}

double ViewshedLocation::minDistance() const
{
  return m_locationViewshed ? m_locationViewshed->minDistance() : m_minDistance;
}

void ViewshedLocation::setMinDistance(double minDistance)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->minDistance() == minDistance)
      return;

    m_minDistance = minDistance;
    m_locationViewshed->setMinDistance(minDistance);
  }
  else
  {
    if (m_minDistance == minDistance)
      return;

    m_minDistance = minDistance;
  }

  emit minDistanceChanged();
}

double ViewshedLocation::maxDistance() const
{
  return m_locationViewshed ? m_locationViewshed->maxDistance() : m_maxDistance;
}

void ViewshedLocation::setMaxDistance(double maxDistance)
{
  m_maxDistance = maxDistance;

  if (m_locationViewshed)
  {
    if (m_locationViewshed->maxDistance() == maxDistance)
      return;

    m_maxDistance = maxDistance;
    m_locationViewshed->setMaxDistance(maxDistance);
  }
  else
  {
    if (m_maxDistance == maxDistance)
      return;

    m_maxDistance = maxDistance;
  }

  emit maxDistanceChanged();
}

double ViewshedLocation::horizontalAngle() const
{
  return m_locationViewshed ? m_locationViewshed->horizontalAngle() : m_horizontalAngle;
}

void ViewshedLocation::setHorizontalAngle(double horizontalAngle)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->horizontalAngle() == horizontalAngle)
      return;

    m_horizontalAngle = horizontalAngle;
    m_locationViewshed->setHorizontalAngle(horizontalAngle);
  }
  else
  {
    if (m_horizontalAngle == horizontalAngle)
      return;

    m_horizontalAngle = horizontalAngle;
  }

  emit horizontalAngleChanged();
}

double ViewshedLocation::verticalAngle() const
{
  return m_locationViewshed ? m_locationViewshed->verticalAngle() : m_veriticalAngle;
}

void ViewshedLocation::setVerticalAngle(double verticalAngle)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->verticalAngle() == verticalAngle)
      return;

    m_veriticalAngle = verticalAngle;
    m_locationViewshed->setVerticalAngle(verticalAngle);
  }
  else
  {
    if (m_veriticalAngle == verticalAngle)
      return;

    m_veriticalAngle = verticalAngle;
  }

  emit verticalAngleChanged();
}

double ViewshedLocation::heading() const
{
  return m_locationViewshed ? m_locationViewshed->heading() : m_heading;
}

void ViewshedLocation::setHeading(double heading)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->heading() == heading)
      return;

    m_heading = heading;
    m_locationViewshed->setHeading(heading);
  }
  else
  {
    if (m_heading == heading)
      return;

    m_heading = heading;
  }

  emit headingChanged();
}

double ViewshedLocation::pitch() const
{
  return m_locationViewshed ? m_locationViewshed->pitch() : m_pitch;
}

void ViewshedLocation::setPitch(double pitch)
{
  if (m_locationViewshed)
  {
    if (m_locationViewshed->pitch() == pitch)
      return;

    m_pitch = pitch;
    m_locationViewshed->setPitch(pitch);
  }
  else
  {
    if (m_pitch == pitch)
      return;

    m_pitch = pitch;
  }

  emit pitchChanged();
}

QColor ViewshedLocation::visibleColor() const
{
  return LocationViewshed::visibleColor();
}

void ViewshedLocation::setVisibleColor(const QColor& visibleColor)
{
  if (LocationViewshed::visibleColor() == visibleColor)
    return;

  LocationViewshed::setVisibleColor(visibleColor);

  emit visibleColorChanged();
}

QColor ViewshedLocation::obstructedColor() const
{
  return LocationViewshed::obstructedColor();
}

void ViewshedLocation::setObstructedColor(const QColor& obstructedColor)
{
  if (LocationViewshed::obstructedColor() == obstructedColor)
    return;

  LocationViewshed::setObstructedColor(obstructedColor);

  emit obstructedColorChanged();
}