qgsmeshvectorrenderer.cpp

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/***************************************************************************
                         qgsmeshvectorrenderer.cpp
                         -------------------------
    begin                : May 2018
    copyright            : (C) 2018 by Peter Petrik
    email                : zilolv at gmail dot com
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#include "qgsmeshvectorrenderer.h"
#include "qgsrendercontext.h"
#include "qgscoordinatetransform.h"
#include "qgsmaptopixel.h"
#include "qgsunittypes.h"
#include "qgsmeshlayerutils.h"

#include <cstdlib>
#include <ctime>
#include <algorithm>
#include <QPen>
#include <QPainter>
#include <cmath>


inline double mag( double input )
{
  if ( input < 0.0 )
  {
    return -1.0;
  }
  return 1.0;
}

inline bool nodataValue( double x, double y )
{
  return ( std::isnan( x ) || std::isnan( y ) );
}

QgsMeshVectorRenderer::QgsMeshVectorRenderer( const QgsTriangularMesh &m,
    const QVector<double> &datasetValuesX,
    const QVector<double> &datasetValuesY,
    const QVector<double> &datasetValuesMag,
    double datasetMagMinimumValue,
    double datasetMagMaximumValue,
    bool dataIsOnVertices,
    const QgsMeshRendererVectorSettings &settings,
    QgsRenderContext &context, QSize size )
  : mTriangularMesh( m )
  , mDatasetValuesX( datasetValuesX )
  , mDatasetValuesY( datasetValuesY )
  , mDatasetValuesMag( datasetValuesMag )
  , mMinMag( datasetMagMinimumValue )
  , mMaxMag( datasetMagMaximumValue )
  , mContext( context )
  , mCfg( settings )
  , mDataOnVertices( dataIsOnVertices )
  , mOutputSize( size )
  , mBufferedExtent( context.extent() )
{
  // should be checked in caller
  Q_ASSERT( !mDatasetValuesMag.empty() );
  Q_ASSERT( !std::isnan( mMinMag ) );
  Q_ASSERT( !std::isnan( mMaxMag ) );

  // we need to expand out the extent so that it includes
  // arrows which start or end up outside of the
  // actual visible extent
  double extension = context.convertToMapUnits( calcExtentBufferSize(), QgsUnitTypes::RenderPixels );
  mBufferedExtent.setXMinimum( mBufferedExtent.xMinimum() - extension );
  mBufferedExtent.setXMaximum( mBufferedExtent.xMaximum() + extension );
  mBufferedExtent.setYMinimum( mBufferedExtent.yMinimum() - extension );
  mBufferedExtent.setYMaximum( mBufferedExtent.yMaximum() + extension );
}

QgsMeshVectorRenderer::~QgsMeshVectorRenderer() = default;

void QgsMeshVectorRenderer::draw()
{
  // Set up the render configuration options
  QPainter *painter = mContext.painter();
  painter->save();
  if ( mContext.flags() & QgsRenderContext::Antialiasing )
    painter->setRenderHint( QPainter::Antialiasing, true );

  QPen pen = painter->pen();
  pen.setCapStyle( Qt::FlatCap );
  pen.setJoinStyle( Qt::MiterJoin );

  double penWidth = mContext.convertToPainterUnits( mCfg.lineWidth(),
                    QgsUnitTypes::RenderUnit::RenderMillimeters );
  pen.setWidthF( penWidth );
  pen.setColor( mCfg.color() );
  painter->setPen( pen );

  const QList<int> trianglesInExtent = mTriangularMesh.faceIndexesForRectangle( mBufferedExtent );

  if ( mCfg.isOnUserDefinedGrid() )
    drawVectorDataOnGrid( trianglesInExtent );
  else if ( mDataOnVertices )
    drawVectorDataOnVertices( trianglesInExtent );
  else
    drawVectorDataOnFaces( trianglesInExtent );

  painter->restore();
}

bool QgsMeshVectorRenderer::calcVectorLineEnd(
  QgsPointXY &lineEnd,
  double &vectorLength,
  double &cosAlpha,
  double &sinAlpha, //out
  const QgsPointXY &lineStart,
  double xVal,
  double yVal,
  double magnitude //in
)
{
  // return true on error

  if ( xVal == 0.0 && yVal == 0.0 )
    return true;

  // do not render if magnitude is outside of the filtered range (if filtering is enabled)
  if ( mCfg.filterMin() >= 0 && magnitude < mCfg.filterMin() )
    return true;
  if ( mCfg.filterMax() >= 0 && magnitude > mCfg.filterMax() )
    return true;

  // Determine the angle of the vector, counter-clockwise, from east
  // (and associated trigs)
  double vectorAngle = -1.0 * atan( ( -1.0 * yVal ) / xVal );
  cosAlpha = cos( vectorAngle ) * mag( xVal );
  sinAlpha = sin( vectorAngle ) * mag( xVal );

  // Now determine the X and Y distances of the end of the line from the start
  double xDist = 0.0;
  double yDist = 0.0;
  switch ( mCfg.shaftLengthMethod() )
  {
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::MinMax:
    {
      double minShaftLength = mContext.convertToPainterUnits( mCfg.minShaftLength(),
                              QgsUnitTypes::RenderUnit::RenderMillimeters );
      double maxShaftLength = mContext.convertToPainterUnits( mCfg.maxShaftLength(),
                              QgsUnitTypes::RenderUnit::RenderMillimeters );
      double minVal = mMinMag;
      double maxVal = mMaxMag;
      double k = ( magnitude - minVal ) / ( maxVal - minVal );
      double L = minShaftLength + k * ( maxShaftLength - minShaftLength );
      xDist = cosAlpha * L;
      yDist = sinAlpha * L;
      break;
    }
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::Scaled:
    {
      double scaleFactor = mCfg.scaleFactor();
      xDist = scaleFactor * xVal;
      yDist = scaleFactor * yVal;
      break;
    }
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::Fixed:
    {
      // We must be using a fixed length
      double fixedShaftLength = mContext.convertToPainterUnits( mCfg.fixedShaftLength(),
                                QgsUnitTypes::RenderUnit::RenderMillimeters );
      xDist = cosAlpha * fixedShaftLength;
      yDist = sinAlpha * fixedShaftLength;
      break;
    }
  }

  // Flip the Y axis (pixel vs real-world axis)
  yDist *= -1.0;

  if ( std::abs( xDist ) < 1 && std::abs( yDist ) < 1 )
    return true;

  // Determine the line coords
  lineEnd = QgsPointXY( lineStart.x() + xDist,
                        lineStart.y() + yDist );

  vectorLength = sqrt( xDist * xDist + yDist * yDist );

  // Check to see if both of the coords are outside the QImage area, if so, skip the whole vector
  if ( ( lineStart.x() < 0 || lineStart.x() > mOutputSize.width() ||
         lineStart.y() < 0 || lineStart.y() > mOutputSize.height() ) &&
       ( lineEnd.x() < 0   || lineEnd.x() > mOutputSize.width() ||
         lineEnd.y() < 0   || lineEnd.y() > mOutputSize.height() ) )
    return true;

  return false; //success
}

double QgsMeshVectorRenderer::calcExtentBufferSize() const
{
  double buffer = 0;
  switch ( mCfg.shaftLengthMethod() )
  {
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::MinMax:
    {
      buffer = mContext.convertToPainterUnits( mCfg.maxShaftLength(),
               QgsUnitTypes::RenderUnit::RenderMillimeters );
      break;
    }
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::Scaled:
    {
      buffer = mCfg.scaleFactor() * mMaxMag;
      break;
    }
    case QgsMeshRendererVectorSettings::ArrowScalingMethod::Fixed:
    {
      buffer = mContext.convertToPainterUnits( mCfg.fixedShaftLength(),
               QgsUnitTypes::RenderUnit::RenderMillimeters );
      break;
    }
  }

  if ( mCfg.filterMax() >= 0 && buffer > mCfg.filterMax() )
    buffer = mCfg.filterMax();

  if ( buffer < 0.0 )
    buffer = 0.0;

  return buffer;
}


void QgsMeshVectorRenderer::drawVectorDataOnVertices( const QList<int> &trianglesInExtent )
{
  const QVector<QgsMeshVertex> &vertices = mTriangularMesh.vertices();
  const QVector<QgsMeshFace> &triangles = mTriangularMesh.triangles();
  QSet<int> drawnVertices;

  // currently expecting that triangulation does not add any new extra vertices on the way
  Q_ASSERT( mDatasetValuesMag.count() == vertices.count() );

  for ( int triangleIndex : trianglesInExtent )
  {
    if ( mContext.renderingStopped() )
      break;

    const QgsMeshFace triangle = triangles[triangleIndex];
    for ( int i : triangle )
    {
      if ( drawnVertices.contains( i ) )
        continue;
      drawnVertices.insert( i );

      const QgsMeshVertex &vertex = vertices.at( i );
      if ( !mBufferedExtent.contains( vertex ) )
        continue;

      double xVal = mDatasetValuesX[i];
      double yVal = mDatasetValuesY[i];
      if ( nodataValue( xVal, yVal ) )
        continue;

      double V = mDatasetValuesMag[i];  // pre-calculated magnitude
      QgsPointXY lineStart = mContext.mapToPixel().transform( vertex.x(), vertex.y() );

      drawVectorArrow( lineStart, xVal, yVal, V );
    }
  }
}

void QgsMeshVectorRenderer::drawVectorDataOnFaces( const QList<int> &trianglesInExtent )
{
  const QVector<QgsMeshVertex> &centroids = mTriangularMesh.centroids();
  const QList<int> nativeFacesInExtent = QgsMeshUtils::nativeFacesFromTriangles( trianglesInExtent,
                                         mTriangularMesh.trianglesToNativeFaces() );
  for ( int i : nativeFacesInExtent )
  {
    if ( mContext.renderingStopped() )
      break;

    QgsPointXY center = centroids.at( i );
    if ( !mBufferedExtent.contains( center ) )
      continue;

    double xVal = mDatasetValuesX[i];
    double yVal = mDatasetValuesY[i];
    if ( nodataValue( xVal, yVal ) )
      continue;

    double V = mDatasetValuesMag[i];  // pre-calculated magnitude
    QgsPointXY lineStart = mContext.mapToPixel().transform( center.x(), center.y() );

    drawVectorArrow( lineStart, xVal, yVal, V );
  }
}

void QgsMeshVectorRenderer::drawVectorDataOnGrid( const QList<int> &trianglesInExtent )
{
  int cellx = mCfg.userGridCellWidth();
  int celly = mCfg.userGridCellHeight();

  const QVector<QgsMeshFace> &triangles = mTriangularMesh.triangles();
  const QVector<QgsMeshVertex> &vertices = mTriangularMesh.vertices();

  for ( const int i : trianglesInExtent )
  {
    if ( mContext.renderingStopped() )
      break;

    const QgsMeshFace &face = triangles[i];

    const int v1 = face[0], v2 = face[1], v3 = face[2];
    const QgsPoint p1 = vertices[v1], p2 = vertices[v2], p3 = vertices[v3];

    const int nativeFaceIndex = mTriangularMesh.trianglesToNativeFaces()[i];

    // Get the BBox of the element in pixels
    QgsRectangle bbox = QgsMeshLayerUtils::triangleBoundingBox( p1, p2, p3 );
    int left, right, top, bottom;
    QgsMeshLayerUtils::boundingBoxToScreenRectangle( mContext.mapToPixel(), mOutputSize, bbox, left, right, top, bottom );

    // Align rect to the grid (e.g. interval <13, 36> with grid cell 10 will be trimmed to <20,30>
    if ( left % cellx != 0 )
      left += cellx - ( left % cellx );
    if ( right % cellx != 0 )
      right -= ( right % cellx );
    if ( top % celly != 0 )
      top += celly - ( top % celly );
    if ( bottom % celly != 0 )
      bottom -= ( bottom % celly );

    for ( int y = top; y <= bottom; y += celly )
    {
      for ( int x = left; x <= right; x += cellx )
      {
        QgsMeshDatasetValue val;
        const QgsPointXY p = mContext.mapToPixel().toMapCoordinates( x, y );

        if ( mDataOnVertices )
        {
          val.setX(
            QgsMeshLayerUtils::interpolateFromVerticesData(
              p1, p2, p3,
              mDatasetValuesX[v1],
              mDatasetValuesX[v2],
              mDatasetValuesX[v3],
              p )
          );
          val.setY(
            QgsMeshLayerUtils::interpolateFromVerticesData(
              p1, p2, p3,
              mDatasetValuesY[v1],
              mDatasetValuesY[v2],
              mDatasetValuesY[v3],
              p )
          );
        }
        else
        {
          val.setX(
            QgsMeshLayerUtils::interpolateFromFacesData(
              p1, p2, p3,
              mDatasetValuesX[nativeFaceIndex],
              p
            )
          );
          val.setY(
            QgsMeshLayerUtils::interpolateFromFacesData(
              p1, p2, p3,
              mDatasetValuesY[nativeFaceIndex],
              p
            )
          );
        }

        if ( nodataValue( val.x(), val.y() ) )
          continue;

        QgsPointXY lineStart( x, y );
        drawVectorArrow( lineStart, val.x(), val.y(), val.scalar() );
      }
    }
  }
}

void QgsMeshVectorRenderer::drawVectorArrow( const QgsPointXY &lineStart, double xVal, double yVal, double magnitude )
{
  QgsPointXY lineEnd;
  double vectorLength;
  double cosAlpha, sinAlpha;
  if ( calcVectorLineEnd( lineEnd, vectorLength, cosAlpha, sinAlpha,
                          lineStart, xVal, yVal, magnitude ) )
    return;

  // Make a set of vector head coordinates that we will place at the end of each vector,
  // scale, translate and rotate.
  QgsPointXY vectorHeadPoints[3];
  QVector<QPointF> finalVectorHeadPoints( 3 );

  double vectorHeadWidthRatio  = mCfg.arrowHeadWidthRatio();
  double vectorHeadLengthRatio = mCfg.arrowHeadLengthRatio();

  // First head point:  top of ->
  vectorHeadPoints[0].setX( -1.0 * vectorHeadLengthRatio );
  vectorHeadPoints[0].setY( vectorHeadWidthRatio * 0.5 );

  // Second head point:  right of ->
  vectorHeadPoints[1].setX( 0.0 );
  vectorHeadPoints[1].setY( 0.0 );

  // Third head point:  bottom of ->
  vectorHeadPoints[2].setX( -1.0 * vectorHeadLengthRatio );
  vectorHeadPoints[2].setY( -1.0 * vectorHeadWidthRatio * 0.5 );

  // Determine the arrow head coords
  for ( int j = 0; j < 3; j++ )
  {
    finalVectorHeadPoints[j].setX( lineEnd.x()
                                   + ( vectorHeadPoints[j].x() * cosAlpha * vectorLength )
                                   - ( vectorHeadPoints[j].y() * sinAlpha * vectorLength )
                                 );

    finalVectorHeadPoints[j].setY( lineEnd.y()
                                   - ( vectorHeadPoints[j].x() * sinAlpha * vectorLength )
                                   - ( vectorHeadPoints[j].y() * cosAlpha * vectorLength )
                                 );
  }

  // Now actually draw the vector
  mContext.painter()->drawLine( lineStart.toQPointF(), lineEnd.toQPointF() );
  mContext.painter()->drawPolygon( finalVectorHeadPoints );
}