Qt Quick 3D - Procedural Texture Example

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

 #include "gradienttexture.h"

 #include <QtCore/QSize>
 #include <QtGui/QGradient>

 GradientTexture::GradientTexture()
 {
     updateTexture();
 }

 int GradientTexture::height() const
 {
     return m_height;
 }

 int GradientTexture::width() const
 {
     return m_width;
 }

 QColor GradientTexture::startColor() const
 {
     return m_startColor;
 }

 QColor GradientTexture::endColor() const
 {
     return m_endColor;
 }

 void GradientTexture::setHeight(int height)
 {
     if (m_height == height)
         return;

     m_height = height;
     emit heightChanged(m_height);
     updateTexture();
 }

 void GradientTexture::setWidth(int width)
 {
     if (m_width == width)
         return;

     m_width = width;
     emit widthChanged(m_width);
     updateTexture();
 }

 void GradientTexture::setStartColor(QColor startColor)
 {
     if (m_startColor == startColor)
         return;

     m_startColor = startColor;
     emit startColorChanged(m_startColor);
     updateTexture();
 }

 void GradientTexture::setEndColor(QColor endColor)
 {
     if (m_endColor == endColor)
         return;

     m_endColor = endColor;
     emit endColorChanged(m_endColor);
     updateTexture();
 }

 void GradientTexture::updateTexture()
 {
     setSize(QSize(m_width, m_height));
     setFormat(QQuick3DTextureData::RGBA8);
     setHasTransparency(false);
     setTextureData(generateTexture());
 }

 QByteArray GradientTexture::generateTexture()
 {
     QByteArray imageData;
     // Create a horizontal gradient between startColor and endColor

     // Create a single scanline and reuse that data for each
     QByteArray gradientScanline;
     gradientScanline.resize(m_width * 4); // RGBA8

     for (int x = 0; x < m_width; ++x) {
         QColor color = linearInterpolate(m_startColor, m_endColor, x / float(m_width));
         int offset = x * 4;
         gradientScanline.data()[offset + 0] = char(color.red());
         gradientScanline.data()[offset + 1] = char(color.green());
         gradientScanline.data()[offset + 2] = char(color.blue());
         gradientScanline.data()[offset + 3] = char(255);
     }

     for (int y = 0; y < m_height; ++y)
         imageData += gradientScanline;

     return imageData;
 }

 QColor GradientTexture::linearInterpolate(const QColor &color1, const QColor &color2, float value)
 {
     QColor output;

     output.setRedF(color1.redF() + (value * (color2.redF() - color1.redF())));
     output.setGreenF(color1.greenF() + (value * (color2.greenF() - color1.greenF())));
     output.setBlueF(color1.blueF() + (value * (color2.blueF() - color1.blueF())));

     return output;
 }