- Qt 6.9
- Qt 3D
- Changes to Qt3D
- Qt 6.9.0 Reference Documentation

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# Changes to Qt3D

Qt 6 is a result of the conscious effort to make the framework more efficient and easy to use.

We try to maintain binary and source compatibility for all the public APIs in each release. But some changes were inevitable in an effort to make Qt a better framework.

In this topic we summarize those changes in Qt3D, and provide guidance to handle them.

## New rendering backend

Over the course of 5.14 and 5.15, the rendering backend was gradually moved into a plugin.

Qt 6 release completes this work and introduces a new RHI based rendering backend which will enable use of Vulkan, Metal or DirectX on the relevant platforms.

The RHI backend is the default but this can be controlled by setting environment variables as explained here.

## Code changes

Some classes have changed modules. In particular, the QBuffer, QAttribute and QGeometry classes (along with associated helper classes) have moved from the Render module to the Core module.

## New API

- Qt3DCore::QGeometryView provides all details for a mesh
- Qt3DCore::QBoundingVolume provides a way of querying or overriding the size of the axis aligned bounding box of a geometry
- Qt3DRender::QPickingProxy provides a way of specifying an alternative (usually simpler) geometry for picking
- Qt3DCore::QAbstractAspect and Qt3DCore::QAspectJob add methods to facilitate and optimize the synchronization of backend operations.

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