// A vertex in vertex buffer consists of position, normal, and texture coordinates
struct Vertex {
    QVector3D position;
    QVector3D normal;
    QVector2D uv;
};

// The vertex buffer
QVector<Vertex> vertices;

// Creates a triangle into the vertex buffer
auto createTriangle = [&](const QVector3D &xyz1, const QVector2D &uv1,
                          const QVector3D &xyz2, const QVector2D &uv2,
                          const QVector3D &xyz3, const QVector2D &uv3) {
    QVector3D n = QVector3D::crossProduct(xyz2 - xyz1, xyz3 - xyz1).normalized();
    vertices.append({xyz1, n, uv1});
    vertices.append({xyz2, n, uv2});
    vertices.append({xyz3, n, uv3});
};

// Pyramid corner coordinates in local space
QVector3D xyz[5] = {{0, 0, 50}, {50, 50, -50}, {50, -50, -50}, {-50, -50, -50}, {-50, 50, -50}};

// Possible texture coordinates for triangle corners
QVector2D uv[4] = {{1, 1}, {1, 0}, {0, 0}, {0, 1}};

// Pyramid consists of four side triangles and a bottom quad made of two triangles
createTriangle(xyz[0], uv[0], xyz[1], uv[1], xyz[2], uv[2]);
createTriangle(xyz[0], uv[0], xyz[2], uv[1], xyz[3], uv[2]);
createTriangle(xyz[0], uv[0], xyz[3], uv[1], xyz[4], uv[2]);
createTriangle(xyz[0], uv[0], xyz[4], uv[1], xyz[1], uv[2]);
createTriangle(xyz[1], uv[0], xyz[4], uv[2], xyz[3], uv[1]);
createTriangle(xyz[1], uv[0], xyz[3], uv[3], xyz[2], uv[2]);

// Make a byte array out of the vertex buffer
QByteArray vertexBuffer(reinterpret_cast<const char *>(vertices.constData()),
                        vertices.size() * int(sizeof(Vertex)));

// Create the geometry. Triangle is the default primitive type, so we don't specify it.
// The order of the added attributes must match the order of the attribute data in the
// vertex buffer.
Q3DSGeometry pyramid;
pyramid.setVertexData(vertexBuffer);
pyramid.addAttribute(Q3DSGeometry::Attribute::PositionSemantic);
pyramid.addAttribute(Q3DSGeometry::Attribute::NormalSemantic);
pyramid.addAttribute(Q3DSGeometry::Attribute::TexCoordSemantic);