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);
}