scatterdatamodifier.cpp Example File

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  #include "scatterdatamodifier.h"
  #include <QtDataVisualization/qscatterdataproxy.h>
  #include <QtDataVisualization/qvalue3daxis.h>
  #include <QtDataVisualization/q3dscene.h>
  #include <QtDataVisualization/q3dcamera.h>
  #include <QtDataVisualization/qscatter3dseries.h>
  #include <QtDataVisualization/q3dtheme.h>
  #include <QtDataVisualization/QCustom3DItem>
  #include <QtCore/qmath.h>

  using namespace QtDataVisualization;

  static const float verticalRange = 8.0f;
  static const float horizontalRange = verticalRange;
  static const float ellipse_a = horizontalRange / 3.0f;
  static const float ellipse_b = verticalRange;
  static const float doublePi = float(M_PI) * 2.0f;
  static const float radiansToDegrees = 360.0f / doublePi;
  static const float animationFrames = 30.0f;

  ScatterDataModifier::ScatterDataModifier(Q3DScatter *scatter)
      : m_graph(scatter),
        m_fieldLines(12),
        m_arrowsPerLine(16),
        m_magneticField(new QScatter3DSeries),
        m_sun(new QCustom3DItem),
        m_magneticFieldArray(0),
        m_angleOffset(0.0f),
        m_angleStep(doublePi / m_arrowsPerLine / animationFrames)
  {
      m_graph->setShadowQuality(QAbstract3DGraph::ShadowQualityNone);
      m_graph->scene()->activeCamera()->setCameraPreset(Q3DCamera::CameraPresetFront);

      // Magnetic field lines use custom narrow arrow
      m_magneticField->setItemSize(0.2f);
      m_magneticField->setMesh(QAbstract3DSeries::MeshUserDefined);
      m_magneticField->setUserDefinedMesh(QStringLiteral(":/mesh/narrowarrow.obj"));
      QLinearGradient fieldGradient(0, 0, 16, 1024);
      fieldGradient.setColorAt(0.0, Qt::black);
      fieldGradient.setColorAt(1.0, Qt::white);
      m_magneticField->setBaseGradient(fieldGradient);
      m_magneticField->setColorStyle(Q3DTheme::ColorStyleRangeGradient);

      // For 'sun' we use a custom large sphere
      m_sun->setScaling(QVector3D(0.07f, 0.07f, 0.07f));
      m_sun->setMeshFile(QStringLiteral(":/mesh/largesphere.obj"));
      QImage sunColor = QImage(2, 2, QImage::Format_RGB32);
      sunColor.fill(QColor(0xff, 0xbb, 0x00));
      m_sun->setTextureImage(sunColor);

      m_graph->addSeries(m_magneticField);
      m_graph->addCustomItem(m_sun);

      // Configure the axes according to the data
      m_graph->axisX()->setRange(-horizontalRange, horizontalRange);
      m_graph->axisY()->setRange(-verticalRange, verticalRange);
      m_graph->axisZ()->setRange(-horizontalRange, horizontalRange);
      m_graph->axisX()->setSegmentCount(int(horizontalRange));
      m_graph->axisZ()->setSegmentCount(int(horizontalRange));

      QObject::connect(&m_rotationTimer, &QTimer::timeout, this,
                       &ScatterDataModifier::triggerRotation);

      toggleRotation();
      generateData();
  }

  ScatterDataModifier::~ScatterDataModifier()
  {
      delete m_graph;
  }

  void ScatterDataModifier::generateData()
  {
      // Reusing existing array is computationally cheaper than always generating new array, even if
      // all data items change in the array, if the array size doesn't change.
      if (!m_magneticFieldArray)
          m_magneticFieldArray = new QScatterDataArray;

      int arraySize = m_fieldLines * m_arrowsPerLine;
      if (arraySize != m_magneticFieldArray->size())
          m_magneticFieldArray->resize(arraySize);

      QScatterDataItem *ptrToDataArray = &m_magneticFieldArray->first();

      for (float i = 0; i < m_fieldLines; i++) {
          float horizontalAngle = (doublePi * i) / m_fieldLines;
          float xCenter = ellipse_a * qCos(horizontalAngle);
          float zCenter = ellipse_a * qSin(horizontalAngle);

          // Rotate - arrow always tangential to origin
          QQuaternion yRotation = QQuaternion::fromAxisAndAngle(0.0f, 1.0f, 0.0f, horizontalAngle * radiansToDegrees);

          for (float j = 0; j < m_arrowsPerLine; j++) {
              // Calculate point on ellipse centered on origin and parallel to x-axis
              float verticalAngle = ((doublePi * j) / m_arrowsPerLine) + m_angleOffset;
              float xUnrotated = ellipse_a * qCos(verticalAngle);
              float y = ellipse_b * qSin(verticalAngle);

              // Rotate the ellipse around y-axis
              float xRotated = xUnrotated * qCos(horizontalAngle);
              float zRotated = xUnrotated * qSin(horizontalAngle);

              // Add offset
              float x = xCenter + xRotated;
              float z = zCenter + zRotated;

              QQuaternion zRotation = QQuaternion::fromAxisAndAngle(0.0f, 0.0f, 1.0f, verticalAngle * radiansToDegrees);
              QQuaternion totalRotation = yRotation * zRotation;

              ptrToDataArray->setPosition(QVector3D(x, y, z));
              ptrToDataArray->setRotation(totalRotation);
              ptrToDataArray++;
          }
      }

      if (m_graph->selectedSeries() == m_magneticField)
          m_graph->clearSelection();

      m_magneticField->dataProxy()->resetArray(m_magneticFieldArray);
  }

  void ScatterDataModifier::setFieldLines(int lines)
  {
      m_fieldLines = lines;
      generateData();
  }

  void ScatterDataModifier::setArrowsPerLine(int arrows)
  {
      m_angleOffset = 0.0f;
      m_angleStep = doublePi / m_arrowsPerLine / animationFrames;
      m_arrowsPerLine = arrows;
      generateData();
  }

  void ScatterDataModifier::triggerRotation()
  {
      m_angleOffset += m_angleStep;
      generateData();
  }

  void ScatterDataModifier::toggleSun()
  {
      m_sun->setVisible(!m_sun->isVisible());
  }

  void ScatterDataModifier::toggleRotation()
  {
      if (m_rotationTimer.isActive())
          m_rotationTimer.stop();
      else
          m_rotationTimer.start(15);
  }