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:

Note: The joint index data is typically I32Type. F32Type is also supported in order to enable functioning with APIs, such as OpenGL ES 2.0, that do not support integer vertex input attributes.

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.

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.

Note: The partial update functions for vertex and index data do not offer any guarantee on how such changes are implemented internally. Depending on the underlying implementation, even partial changes may lead to updating the entire graphics resource.

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

Sets the primitive type used for rendering to type.

The initial value is Triangles.

Note: Be aware that triangle fans (TriangleFan) may not be supported at run time, depending on the underlying graphics API. For example, with Direct 3D this topology will not be functional at all.

Note: The point size for Points and the line width for Lines and LineStrip are controlled by the material. Be aware however that sizes other than 1 may not be supported at run time, depending on the underlying graphics API.

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.)

Note: QQuick3DGeometry expects, and works only with, vertex data with an interleaved attribute layout.

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.

Note: The partial update functions for vertex and index data do not offer any guarantee on how such changes are implemented internally. Depending on the underlying implementation, even partial changes may lead to updating the entire graphics resource.

int QQuick3DGeometry::stride() const

Returns the byte stride of the vertex buffer.

See also setStride.

QByteArray QQuick3DGeometry::vertexData() const

Returns the vertex buffer data set by setVertexData.

See also setVertexData().