QWaitFence Class

(Qt3DRender::QWaitFence)

FrameGraphNode used to wait for a fence in the graphics command stream to become signaled. More...

Header:	#include <QWaitFence>
qmake:	QT += 3drender
Since:	Qt 5.13
Inherits:	Qt3DRender::QFrameGraphNode

This class was introduced in Qt 5.13.

• List of all members, including inherited members

Properties

• handle : QVariant
• handleType : HandleType
• timeout : quint64
• waitOnCPU : bool

Public Functions

QVariant	handle() const
Qt3DRender::QWaitFence::HandleType	handleType() const
void	setHandle(QVariant handle)
void	setHandleType(Qt3DRender::QWaitFence::HandleType type)
void	setTimeout(quint64 timeout)
void	setWaitOnCPU(bool waitOnCPU)
quint64	timeout() const
bool	waitOnCPU() const

Signals

void	handleChanged(QVariant handle)
void	handleTypeChanged(Qt3DRender::QWaitFence::HandleType handleType)
void	timeoutChanged(quint64 timeoutChanged)
void	waitOnCPUChanged(bool waitOnCPU)

Detailed Description

Fence allow to synchronosize GPU and CPU workloads. GPU commands usually are non-blocking. When issued, commands are inserted in command buffers which will be read at a later time by the GPU. In some cases, you want to continue processing or issue specific command only when you are sure a command has been executed by the hardware. Fences are a way to do so. This is especially important when using 3rd party engines with Qt3D, Qt3D should only access shared resources when we know the other engine command are done modifying the resource.

QWaitFence is a FrameGraph node that will force to wait for it to become signaled before subsequent commands are inserted into the command stream. It can then be used in conjunction with QSetFence and contains properties to configure how long it should wait and whether it should block on the CPU side.

Note: Qt 3D uploads GPU resources (Texture, Shaders, Buffers) before issuing draw calls.