Hello Qt Quick 3D Example | Qt Quick 3D 6.7.2
Description: Demonstrates simple instanced drawing.

- Qt 6.7
- Qt Quick 3D
- Qt Quick 3D Examples and Tutorials
- Hello Qt Quick 3D Example
- Qt Quick 3D | Commercial or GPLv3

# Hello Qt Quick 3D Example

     // Copyright (C) 2020 The Qt Company Ltd.
     // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

     #include "imageinstancetable.h"
     #include <math.h>
     #include <QMatrix4x4>
     #include <QColor>
     #include <QImage>
     #include <QQmlFile>

     ImageInstanceTable::ImageInstanceTable(QQuick3DObject *parent) : QQuick3DInstancing(parent)
     {
     }

     ImageInstanceTable::~ImageInstanceTable()
     {
     }

     int ImageInstanceTable::gridSize() const
     {
         return m_gridSize;
     }

     float ImageInstanceTable::gridSpacing() const
     {
         return m_gridSpacing;
     }

     QString ImageInstanceTable::image() const
     {
         return m_imageSource;
     }

     void ImageInstanceTable::setGridSize(int gridSize)
     {
         if (m_gridSize == gridSize)
             return;

         m_gridSize = gridSize;
         emit gridSizeChanged(m_gridSize);
         markDirty();
         m_dirty = true;
     }

     void ImageInstanceTable::setGridSpacing(float gridSpacing)
     {
         if (qFuzzyCompare(m_gridSpacing, gridSpacing))
             return;

         m_gridSpacing = gridSpacing;
         emit gridSpacingChanged(m_gridSpacing);
         markDirty();
         m_dirty = true;
     }

     void ImageInstanceTable::setImage(QString image)
     {
         if (m_imageSource == image)
             return;

         m_imageSource = image;
         emit imageChanged(m_imageSource);
         markDirty();
         m_dirty = true;
     }

     QByteArray ImageInstanceTable::getInstanceBuffer(int *instanceCount)
     {
         if (m_dirty) {
             QImage image(m_imageSource);
             if (image.isNull())
                 qWarning() << "Could not load image" << m_imageSource;
             m_instanceData.resize(0);
             image = image.scaledToWidth(m_gridSize, Qt::SmoothTransformation);
             int instanceNumber = 0;
             for (int blockX = 0; blockX < image.width(); ++blockX) {
                 float xPos = m_gridSpacing * (blockX - m_gridSize/2);
                 for (int blockY = 0; blockY < image.width(); ++blockY) {
                     QColor color = image.pixel(blockX, blockY);
                     float yPos = -m_gridSpacing * (blockY - m_gridSize/2);

                     float zPos = 10 * m_gridSpacing * (color.lightnessF() - 1.0);

                     auto entry = calculateTableEntry({xPos,yPos,zPos}, {1.0, 1.0, 1.0}, {0,0,0}, color, {});
                     m_instanceData.append(reinterpret_cast<const char *>(&entry), sizeof(entry));
                     instanceNumber++;
                 }
             }
             m_instanceCount = instanceNumber;
             m_dirty = false;
         }
         if (instanceCount)
             *instanceCount = m_instanceCount;

         return m_instanceData;
     }