qgstessellatedpolygongeometry.cpp

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/***************************************************************************
  qgstessellatedpolygongeometry.cpp
  --------------------------------------
  Date                 : July 2017
  Copyright            : (C) 2017 by Martin Dobias
  Email                : wonder dot sk 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 "qgstessellatedpolygongeometry.h"
 
#include <Qt3DRender/QAttribute>
#include <Qt3DRender/QBuffer>
#include <Qt3DRender/QBufferDataGenerator>
 
#include "qgstessellator.h"
 
#include "qgspoint.h"
#include "qgspolygon.h"
 
 
QgsTessellatedPolygonGeometry::QgsTessellatedPolygonGeometry( bool _withNormals, bool _invertNormals, bool _addBackFaces, bool _addTextureCoords, QNode *parent )
  : Qt3DRender::QGeometry( parent ),
    mWithNormals( _withNormals ),
    mInvertNormals( _invertNormals ),
    mAddBackFaces( _addBackFaces ),
    mAddTextureCoords( _addTextureCoords )
{
  mVertexBuffer = new Qt3DRender::QBuffer( this );
 
  const QgsTessellator tmpTess( 0, 0, mWithNormals, false, false, false, mAddTextureCoords );
  const int stride = tmpTess.stride();
 
  mPositionAttribute = new Qt3DRender::QAttribute( this );
  mPositionAttribute->setName( Qt3DRender::QAttribute::defaultPositionAttributeName() );
  mPositionAttribute->setVertexBaseType( Qt3DRender::QAttribute::Float );
  mPositionAttribute->setVertexSize( 3 );
  mPositionAttribute->setAttributeType( Qt3DRender::QAttribute::VertexAttribute );
  mPositionAttribute->setBuffer( mVertexBuffer );
  mPositionAttribute->setByteStride( stride );
  mPositionAttribute->setByteOffset( 0 );
  addAttribute( mPositionAttribute );
 
  if ( mWithNormals )
  {
    mNormalAttribute = new Qt3DRender::QAttribute( this );
    mNormalAttribute->setName( Qt3DRender::QAttribute::defaultNormalAttributeName() );
    mNormalAttribute->setVertexBaseType( Qt3DRender::QAttribute::Float );
    mNormalAttribute->setVertexSize( 3 );
    mNormalAttribute->setAttributeType( Qt3DRender::QAttribute::VertexAttribute );
    mNormalAttribute->setBuffer( mVertexBuffer );
    mNormalAttribute->setByteStride( stride );
    mNormalAttribute->setByteOffset( 3 * sizeof( float ) );
    addAttribute( mNormalAttribute );
  }
  if ( mAddTextureCoords )
  {
    mTextureCoordsAttribute = new Qt3DRender::QAttribute( this );
    mTextureCoordsAttribute->setName( Qt3DRender::QAttribute::defaultTextureCoordinateAttributeName() );
    mTextureCoordsAttribute->setVertexBaseType( Qt3DRender::QAttribute::Float );
    mTextureCoordsAttribute->setVertexSize( 2 );
    mTextureCoordsAttribute->setAttributeType( Qt3DRender::QAttribute::VertexAttribute );
    mTextureCoordsAttribute->setBuffer( mVertexBuffer );
    mTextureCoordsAttribute->setByteStride( stride );
    mTextureCoordsAttribute->setByteOffset( mWithNormals ? 6 * sizeof( float ) : 3 * sizeof( float ) );
    addAttribute( mTextureCoordsAttribute );
  }
}
 
void QgsTessellatedPolygonGeometry::setPolygons( const QList<QgsPolygon *> &polygons, const QList<QgsFeatureId> &featureIds, const QgsPointXY &origin, float extrusionHeight, const QList<float> &extrusionHeightPerPolygon )
{
  Q_ASSERT( polygons.count() == featureIds.count() );
  mTriangleIndexStartingIndices.reserve( polygons.count() );
  mTriangleIndexFids.reserve( polygons.count() );
 
  QgsTessellator tessellator( origin.x(), origin.y(), mWithNormals, mInvertNormals, mAddBackFaces, false, mAddTextureCoords );
  for ( int i = 0; i < polygons.count(); ++i )
  {
    Q_ASSERT( tessellator.dataVerticesCount() % 3 == 0 );
    const uint startingTriangleIndex = static_cast<uint>( tessellator.dataVerticesCount() / 3 );
    mTriangleIndexStartingIndices.append( startingTriangleIndex );
    mTriangleIndexFids.append( featureIds[i] );
 
    QgsPolygon *polygon = polygons.at( i );
    const float extr = extrusionHeightPerPolygon.isEmpty() ? extrusionHeight : extrusionHeightPerPolygon.at( i );
    tessellator.addPolygon( *polygon, extr );
  }
 
  qDeleteAll( polygons );
 
  const QByteArray data( ( const char * )tessellator.data().constData(), tessellator.data().count() * sizeof( float ) );
  const int nVerts = data.count() / tessellator.stride();
 
  mVertexBuffer->setData( data );
  mPositionAttribute->setCount( nVerts );
  if ( mNormalAttribute )
    mNormalAttribute->setCount( nVerts );
  if ( mAddTextureCoords )
    mTextureCoordsAttribute->setCount( nVerts );
}
 
void QgsTessellatedPolygonGeometry::setData( const QByteArray &vertexBufferData, int vertexCount, const QVector<QgsFeatureId> &triangleIndexFids, const QVector<uint> &triangleIndexStartingIndices )
{
  mTriangleIndexStartingIndices = triangleIndexStartingIndices;
  mTriangleIndexFids = triangleIndexFids;
 
  mVertexBuffer->setData( vertexBufferData );
  mPositionAttribute->setCount( vertexCount );
  if ( mNormalAttribute )
    mNormalAttribute->setCount( vertexCount );
  if ( mTextureCoordsAttribute )
    mTextureCoordsAttribute->setCount( vertexCount );
}
 
 
// run binary search on a sorted array, return index i where data[i] <= x < data[i+1]
static int binary_search( uint v, const uint *data, int count )
{
  int idx0 = 0;
  int idx1 = count - 1;
 
  if ( v < data[0] || v >= data[count - 1] )
    return -1;  // not in the array
 
  while ( idx0 != idx1 )
  {
    const int idxPivot = ( idx0 + idx1 ) / 2;
    const uint pivot = data[idxPivot];
    if ( pivot <= v )
    {
      if ( data[idxPivot + 1] > v )
        return idxPivot;   // we're done!
      else  // continue searching values greater than the pivot
        idx0 = idxPivot;
    }
    else   // continue searching values lower than the pivot
      idx1 = idxPivot;
  }
  return idx0;
}
 
 
QgsFeatureId QgsTessellatedPolygonGeometry::triangleIndexToFeatureId( uint triangleIndex ) const
{
  const int i = binary_search( triangleIndex, mTriangleIndexStartingIndices.constData(), mTriangleIndexStartingIndices.count() );
  return i != -1 ? mTriangleIndexFids[i] : FID_NULL;
}