QBufferDataGenerator

Provides a mechanism to generate buffer data from a job. More

Detailed Description

The QBufferDataGenerator should be subclassed to provide a way to fill the data of a QBuffer . Such functors are executed at runtime in a Qt 3D job (likely in parallel with many other jobs). When providing a functor you must implement the operator() which will be called to generate the actual data. You must make sure that you have stored copies of anything you might need for it to execute properly. You should also implement the operator==. It will be used to compare with other functors and based on that allow the renderer to decide if a new functor should be executed or not.

Note

functors are useful when you can build data from a few set of attributes (e.g: building a sphere from a radius property). If you already have access to the buffer data, using Qt3DRender::QBuffer::setData() is likely more efficient.

QByteArray createSphereMeshVertexData(float radius, int rings, int slices)
{
    ...
}

class SphereVertexDataFunctor : public QBufferDataGenerator
{
public:
    SphereVertexDataFunctor(int rings, int slices, float radius)
        : m_rings(rings)
        , m_slices(slices)
        , m_radius(radius)
    {}

    QByteArray operator ()() override
    {
        return createSphereMeshVertexData(m_radius, m_rings, m_slices);
    }

    bool operator ==(const QBufferDataGenerator &other) const override
    {
        const SphereVertexDataFunctor *otherFunctor = functor_cast<SphereVertexDataFunctor>(&other);
        if (otherFunctor != nullptr)
            return (otherFunctor->m_rings == m_rings &&
                    otherFunctor->m_slices == m_slices &&
                    otherFunctor->m_radius == m_radius);
        return false;
    }

    QT3D_FUNCTOR(SphereVertexDataFunctor)

private:
    int m_rings;
    int m_slices;
    float m_radius;
};

The QT3D_FUNCTOR macro should be added when subclassing. This allows you to use functor_cast in your comparison operator to make sure that the other functor is of the same type as the one your are trying to compare against.

class PySide2.Qt3DRender.QBufferDataGenerator
PySide2.Qt3DRender.QBufferDataGenerator.__eq__(other)
Parameters

otherPySide2.Qt3DRender.QBufferDataGenerator

Return type

bool

Should be reimplemented to return true when two generators (the one you are comparing against and the other generator) are identical, false otherwise.

Note

The renderer uses this comparison to decide whether data for a buffer needs to be reuploaded or not when the functor on a QBuffer changes.