// 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);

Member Function Documentation

Q3DSGeometry::Q3DSGeometry()

Constructs a new Q3DSGeometry instance.

[virtual] Q3DSGeometry::~Q3DSGeometry()

Destructor.

void Q3DSGeometry::addAttribute(Attribute::Semantic semantic, Attribute::ComponentType componentType = Attribute::DefaultType)

Sets an attribute to this geometry. The geometry attributes specify how the data in vertex and index buffers should be interpreted. Each attribute is composed of a semantic, which indicates which vertex attribute this attribute refers to and componentType, which indicates the data type of each component of the attribute data. The semantic also determines the component count in vertex buffer for the attribute. The component count is two for TexCoordSemantic and three for other vertex buffer semantics. Component count for index buffer is always one.

For example, PositionSemantic specifies the vertex position in local space, so it is composed of three components: x, y, and z-coordinates.

The order of addAttribute calls must match the order of the attributes in vertex data. The order is relevant as it is used to calculate the offset and stride of each attribute.

void Q3DSGeometry::addAttribute(const Q3DSGeometry::Attribute &att)

Sets an attribute att to this geometry.

See also addAttribute.

Q3DSGeometry::Attribute Q3DSGeometry::attribute(int idx) const

Returns an added attribute with index idx.

See also addAttribute and attributeCount.

int Q3DSGeometry::attributeCount() const

Returns the number of attributes set to this geometry.

See also addAttribute.

void Q3DSGeometry::clear()

Removes all added attributes and buffers and resets the geometry to an uninitialized state.

See also primitiveType.

const QByteArray &Q3DSGeometry::indexBuffer() const

Returns the currently set index buffer data.

See also setIndexData.

QByteArray &Q3DSGeometry::indexBuffer()

This is an overloaded function.

Q3DSGeometry::PrimitiveType Q3DSGeometry::primitiveType() const

Returns the primitive type of this geometry.

See also setPrimitiveType.

void Q3DSGeometry::setIndexData(const QByteArray &data)

Sets the index buffer to data. You must also add an attribute with IndexSemantic to the geometry.

See also addAttribute, indexBuffer, and Attribute::Semantic.

void Q3DSGeometry::setPrimitiveType(Q3DSGeometry::PrimitiveType type)

Sets the primitive type of this geometry to type.

See also primitiveType.

void Q3DSGeometry::setVertexData(const QByteArray &data)

Sets the vertex buffer to data. The data must contain all attribute data in interleaved format. You must also add attributes to the geometry to specify how the vertex buffer data should be interpreted.

See also addAttribute and vertexBuffer.

const QByteArray &Q3DSGeometry::vertexBuffer() const

Returns the currently set vertex buffer data.

See also setVertexData.

QByteArray &Q3DSGeometry::vertexBuffer()

This is an overloaded function.