QQuick3DGeometry Class

class CustomGeometry : public QQuick3DGeometry
{
public:
    CustomGeometry() { rebuildGeometry(); }

    void setSomething() {
       // Change relevant internal data.
       // ...

       // Then rebuild the vertex and index data and pass it to QQuick3DGeometry.
       rebuildGeometry();

       // Finally, trigger an update. This is relevant in case nothing else
       // is changing in the scene; this way we make sure a new frame will
       // be rendered.
       update();
    }

private:
    void rebuildGeometry()
    {
        QByteArray vertices;
        QByteArray indices;
        ...
        setPrimitiveType(Lines);
        setVertexBuffer(vertices);
        setIndexBuffer(indices);
        setStride(3 * sizeof(float)); // e.g. when having 3 components per vertex
        setBounds(...); // minimum and maximum extents, for picking
        addAttribute(PositionSemantic, 0, F32Type);
        ...
    }
};

qmlRegisterType<CustomGeometry>("Example", 1, 0, "CustomGeometry");

CONFIG += qmltypes
QML_IMPORT_NAME = Example
QML_IMPORT_MAJOR_VERSION = 1

qt_add_qml_module(application
    URI Example
    VERSION 1.0
)

class CustomGeometry : public QQuick3DGeometry
{
    Q_OBJECT
    QML_NAMED_ELEMENT(CustomGeometry)
    ...
};

import Example 1.0

Model {
    id: customModel
    geometry: CustomGeometry {
    }
}

class ExampleGeometry : public QQuick3DGeometry
{
    Q_OBJECT
    QML_NAMED_ELEMENT(ExampleGeometry)

public:
    ExampleGeometry();

private:
    void updateData();
};

ExampleGeometry::ExampleGeometry()
{
    updateData();
}

void ExampleGeometry::updateData()
{
    QByteArray v;
    v.resize(3 * 3 * sizeof(float));
    float *p = reinterpret_cast<float *>(v.data());

    // a triangle, front face = counter-clockwise
    *p++ = -1.0f; *p++ = -1.0f; *p++ = 0.0f;
    *p++ = 1.0f; *p++ = -1.0f; *p++ = 0.0f;
    *p++ = 0.0f; *p++ = 1.0f; *p++ = 0.0f;

    setVertexData(v);
    setStride(3 * sizeof(float));

    setPrimitiveType(QQuick3DGeometry::PrimitiveType::Triangles);

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

Member Function Documentation

void QQuick3DGeometry::addAttribute(Attribute::Semantic semantic, int offset, Attribute::ComponentType componentType)

Adds vertex attribute description. Each attribute has a semantic, which specifies the usage of the attribute and the number of components it has, an offset from the beginning to the vertex to the attribute location inside a vertex and a componentType specifying the datatype and size of the attribute.

The semantic can be one of the following:

In addition, semantic can be IndexSemantic. In this case the attribute does not represent an entry in the vertex buffer, but rather describes the index data in the index buffer. Since there is always just one index per vertex, offset makes no sense for the index buffer, and should be left at zero.

The component type can be one of the following:

void QQuick3DGeometry::addAttribute(const QQuick3DGeometry::Attribute &attribute)

This is an overloaded function.

Adds vertex attribute description. Each attribute has a semantic, which specifies the usage of the attribute and the number of components it has, an offset from the beginning to the vertex to the attribute location inside a vertex and a componentType specifying the datatype and size of the attribute.

void QQuick3DGeometry::addSubset(int offset, int count, const QVector3D &boundsMin, const QVector3D &boundsMax, const QString &name = {})

Adds new subset to the geometry. Subsets allow rendering parts of the geometry with different materials. The materials are specified in the model.

If the geometry has index buffer, then the offset and count are the primitive offset and count of indices in the subset. If the geometry has only vertex buffer, the offset is the vertex offset and count is the number of vertices in the subset.

The bounds boundsMin and boundsMax should enclose the subset just like geometry bounds. Also the subset can have a name.

QQuick3DGeometry::Attribute QQuick3DGeometry::attribute(int index) const

Returns attribute definition number index

The attribute definitions are numbered from 0 to attributeCount() - 1

int QQuick3DGeometry::attributeCount() const

Returns the number of attributes defined for this geometry.

See also attribute.

QVector3D QQuick3DGeometry::boundsMax() const

Returns the maximum coordinate of the bounding volume.

See also setBounds.

QVector3D QQuick3DGeometry::boundsMin() const

Returns the minimum coordinate of the bounding volume.

See also setBounds.

void QQuick3DGeometry::clear()

Resets the geometry to its initial state, clearing previously set vertex and index data as well as attributes.

QByteArray QQuick3DGeometry::indexData() const

Returns the index buffer data.

See also setIndexData().

QQuick3DGeometry::PrimitiveType QQuick3DGeometry::primitiveType() const

Returns the primitive type used when rendering. The default is Triangles.

See also setPrimitiveType.

void QQuick3DGeometry::setBounds(const QVector3D &min, const QVector3D &max)

Sets the bounding volume of the geometry to the cube defined by the points min and max. This is used for picking.

void QQuick3DGeometry::setIndexData(const QByteArray &data)

Sets the index buffer to data. To use indexed drawing, add an attribute with IndexSemantic

See also indexData() and addAttribute.

void QQuick3DGeometry::setIndexData(int offset, const QByteArray &data)

This is an overloaded function.

Updates a subset of the index buffer. offset specifies the offset in bytes, data specifies the size and the data.

This function will not resize the buffer. If offset + data.size() is greater than the current size of the buffer, the overshooting data will be ignored.

void QQuick3DGeometry::setPrimitiveType(QQuick3DGeometry::PrimitiveType type)

Sets the primitive type used for rendering to type.

The initial value is Triangles.

See also primitiveType().

void QQuick3DGeometry::setStride(int stride)

Sets the stride of the vertex buffer to stride, measured in bytes. This is the distance between two consecutive vertices in the buffer.

For example, a tightly packed, interleaved vertex buffer for a geometry using PositionSemantic, IndexSemantic, and ColorSemantic will have a stride of 28 (Seven floats in total: Three for position, four for color, and none for indexes, which do not go in the vertex buffer.)

See also stride() and addAttribute.

void QQuick3DGeometry::setVertexData(const QByteArray &data)

Sets the vertex buffer data. The buffer should hold all the vertex data packed in the array, as described by the attribute definitions. Note that this does not include attributes with IndexSemantic, which belong in the index buffer.

See also vertexData(), addAttribute, setStride, and setIndexData.

void QQuick3DGeometry::setVertexData(int offset, const QByteArray &data)

This is an overloaded function.

Updates a subset of the vertex buffer. offset specifies the offset in bytes, data specifies the size and the data.

This function will not resize the buffer. If offset + data.size() is greater than the current size of the buffer, the overshooting data will be ignored.

int QQuick3DGeometry::stride() const

Returns the byte stride of the vertex buffer.

See also setStride.

QVector3D QQuick3DGeometry::subsetBoundsMax(int subset) const

Returns the number of maximum bounds of a subset.

See also subsetBoundsMin.

QVector3D QQuick3DGeometry::subsetBoundsMin(int subset) const

Returns the number of minimum bounds of a subset.

See also subsetBoundsMax.

int QQuick3DGeometry::subsetCount() const

Returns the number of subsets.

int QQuick3DGeometry::subsetCount(int subset) const

Returns the subset primitive count.

See also subsetOffset.

QString QQuick3DGeometry::subsetName(int subset) const

Returns the subset name.

int QQuick3DGeometry::subsetOffset(int subset) const

Returns the subset offset to the vertex or index buffer.

See also subsetCount.

QByteArray QQuick3DGeometry::vertexData() const

Returns the vertex buffer data set by setVertexData.

See also setVertexData().