Cross-platform applications can use Qt to display graphical elements. Qt abstracts the platforms' underlying graphics APIs so that developers can focus on the application code.
The Qt Rendering Hardware Interface (RHI) translates 3D graphics call from Qt applications to the available graphics APIs on the target platform.
The supported graphics APIs are:
- OpenGL (version 3 and higher)
- OpenGL ES (version 2 and higher)
- Vulkan (1.0 and higher)
- Direct3D 11 (11.1 and higher)
Graphics in Qt Quick
Qt Quick applications use a scene graph for rendering. The scene graph renderer can create efficient graphics calls and increase performance. The scene graph is has an accessible API which gives you the flexibility to create complex but fast graphics.
The pages in the following list contain more information about rendering Qt Quick applications.
- Qt Quick Scene Graph
- Scene Graph and Rendering
- Qt Quick Scene Graph Default Renderer
- OpenGL and Qt Quick 2.0 - How to integrate application-provided graphics commands (OpenGL, Vulkan, Direct3D, etc.) into a Qt Quick scene graph.
Qt Quick can also be rendered using Qt Quick 2D Renderer. This raster paint engine enables rendering Qt Quick applications on platforms that do not have OpenGL.
Choosing a Rendering Path
Qt uses the target platform's graphics APIs whenever possible, however, it is possible to set up Qt's rendering path with a specific API. In many cases, choosing a specific API can increase performance and allows the developers to deploy on a platform that have a specific graphics API. Visit the Rendering via the Qt Rendering Hardware Interface page on how to set the render path in QQuickWindow.
3D Graphics with Qt Quick 3D
Qt Quick 3D is an add-on that provides a high-level API for creating 3D content and 3D user interfaces based on Qt Quick. It extends the Qt Quick Scene Graph which lets you implement 3D content on 2D Qt Quick applications.
The Qt Shader Tools provides a tool, QSB, to translate vertex and fragment shaders into a package for Qt Quick interfaces. In particular, the ShaderEffect QML type and QSGMaterial subclasses can use the output of QSB. Qt Quick 3D has its own framework for importing shaders into 3D scenes.
The following list contains information about shader effects.
- Qt Shader Tools
- Programmable Materials, Effects, Geometry, and Texture data - materials and shaders in Qt Quick 3D
High-Level Graphics with Qt GUI
Qt GUI provides a high level windowing, painting, and typography system. QPainter provides an API for drawing vector graphics, text and images onto different surfaces, or QPaintDevice instances, such as QImage, QOpenGLPaintDevice, QWidget, and QPrinter. For Qt Widgets user interfaces, Qt uses a software renderer.
The following list contains information about Qt GUIs high-level drawing APIs.
Qt OpenGL Module
The Qt OpenGL module is for applications that require OpenGL access. This module is to maintain compatibility with Qt 5 applications and with Qt GUI. For user interfaces that use QWidget, QOpenGLWidget is a widget that can add OpenGL scenes.
Qt supports printing both directly to actual printers, locally or on the network, as well as producing PDF output. How to do printing with Qt is described in detail on the Qt Print Support page.
Qt supports convenient reading, writing, and manipulating of images through the QImage class. In addition, for more fine grained control of how images are loaded or saved, you can use the QImageReader and QImageWriter classes respectively. To add support for additional image formats, outside of the ones provided by Qt, you can create image format plugins by using QImageIOHandler and QImageIOPlugin.
See the Reading and Writing Image Files page for more information.