Qt Quick 3D - Volumetric Rendering Example

 // Copyright (C) 2023 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

 #include "lineboxgeometry.h"
 #include <QRandomGenerator>
 #include <QVector3D>
 #include <array>

 LineBoxGeometry::LineBoxGeometry()
 {
     constexpr int kStride = sizeof(QVector3D);

     QByteArray vertexData(24 * kStride, Qt::Initialization::Uninitialized);
     QVector3D *p = reinterpret_cast<QVector3D *>(vertexData.data());

     std::array<QVector3D, 8> pts;
     pts[0] = QVector3D(-50, -50, -50);
     pts[1] = QVector3D(-50, -50, +50);
     pts[2] = QVector3D(-50, +50, +50);
     pts[3] = QVector3D(-50, +50, -50);
     pts[4] = QVector3D(+50, -50, -50);
     pts[5] = QVector3D(+50, -50, +50);
     pts[6] = QVector3D(+50, +50, +50);
     pts[7] = QVector3D(+50, +50, -50);
     // left side
     *p = pts[0];
     p++;
     *p = pts[1];
     p++;
     *p = pts[1];
     p++;
     *p = pts[2];
     p++;
     *p = pts[2];
     p++;
     *p = pts[3];
     p++;
     *p = pts[3];
     p++;
     *p = pts[0];
     p++;
     // right side
     *p = pts[4];
     p++;
     *p = pts[5];
     p++;
     *p = pts[5];
     p++;
     *p = pts[6];
     p++;
     *p = pts[6];
     p++;
     *p = pts[7];
     p++;
     *p = pts[7];
     p++;
     *p = pts[4];
     p++;
     // across
     *p = pts[0];
     p++;
     *p = pts[4];
     p++;
     *p = pts[1];
     p++;
     *p = pts[5];
     p++;
     *p = pts[2];
     p++;
     *p = pts[6];
     p++;
     *p = pts[3];
     p++;
     *p = pts[7];
     p++;

     setVertexData(vertexData);
     setStride(kStride);
     setBounds(QVector3D(-50.0f, -50.0f, -50.0f), QVector3D(+50.0f, +50.0f, +50.0f));

     setPrimitiveType(QQuick3DGeometry::PrimitiveType::Lines);

     addAttribute(QQuick3DGeometry::Attribute::PositionSemantic, 0, QQuick3DGeometry::Attribute::F32Type);
 }