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;
 }