QLevelOfDetail Class

(Qt3DRender::QLevelOfDetail)

The QLevelOfDetail class provides a way of controlling the complexity of rendered entities based on their size on the screen. More...

Header:	#include <QLevelOfDetail>
qmake:	QT += 3drender
Since:	Qt 5.9
Instantiated By:	LevelOfDetail
Inherits:	Qt3DCore::QComponent
Inherited By:	Qt3DRender::QLevelOfDetailSwitch

This class was introduced in Qt 5.9.

• List of all members, including inherited members

Public Types

enum	ThresholdType { DistanceToCameraThreshold, ProjectedScreenPixelSizeThreshold }

Properties

camera : Qt3DRender::QCamera* currentIndex : int thresholdType : ThresholdType

thresholds : QVector<qreal> volumeOverride : Qt3DRender::QLevelOfDetailBoundingSphere

Public Functions

	QLevelOfDetail(Qt3DCore::QNode *parent = nullptr)
Qt3DRender::QCamera *	camera() const
int	currentIndex() const
Qt3DRender::QLevelOfDetail::ThresholdType	thresholdType() const
QVector<qreal>	thresholds() const
Qt3DRender::QLevelOfDetailBoundingSphere	volumeOverride() const

Public Slots

void	setCamera(Qt3DRender::QCamera *camera)
void	setCurrentIndex(int currentIndex)
void	setThresholdType(Qt3DRender::QLevelOfDetail::ThresholdType thresholdType)
void	setThresholds(const QVector<qreal> &thresholds)
void	setVolumeOverride(const Qt3DRender::QLevelOfDetailBoundingSphere &volumeOverride)

Signals

void	cameraChanged(Qt3DRender::QCamera *camera)
void	currentIndexChanged(int currentIndex)
void	thresholdTypeChanged(Qt3DRender::QLevelOfDetail::ThresholdType thresholdType)
void	thresholdsChanged(const QVector<qreal> &thresholds)
void	volumeOverrideChanged(const Qt3DRender::QLevelOfDetailBoundingSphere &volumeOverride)

Detailed Description

QLevelOfDetail can be used to control the representation of an entity based on distance from the observer or size on the screen.

In order to improve rendering performance, objects that are very small can be rendered using far fewer details, in geometry or texture.

The component is controlled by specifying thresholds of values which are interpreted as either distances from the camera or screen size.

As the point of view changes, the currentIndex property will change to reflect matching value in the range array.

The currentIndex property can then be used, for example, to enable or disable entities, change material, etc.

The LevelOfDetail component is not shareable between multiple entities.

 #include <Qt3DCore/QEntity>
 #include <Qt3DRender/QGeometryRenderer>
 #include <Qt3DRender/QLevelOfDetail>

// Scene
Qt3DCore::QEntity *rootEntity = new Qt3DCore::Qt3DCore::QEntity;

Qt3DCore::QEntity *renderableEntity = new Qt3DCore::QEntity(rootEntity);
Qt3DRender::QGeometryRenderer *geometryRenderer = new Qt3DCore::QGeometryRenderer(renderableEntity);
renderableEntity->addComponent(geometryRenderer);
Qt3DRender::QLevelOfDetail* lod = new Qt3Render::QLevelOfDetail(renderableEntity);
QVector<qreal> thresholds = {20, 35, 50, 65};
lod->setThresholds(thresholds);
lod->setCamera(mainCamera);
renderableEntity->addComponent(lod);

// connect to QLevelOfDetail::currentIndexChanged to toggle rendering
...

Member Type Documentation

enum QLevelOfDetail::ThresholdType

Specifies how the values in the thresholds are interpreted

Constant	Value	Description
Qt3DRender::QLevelOfDetail::DistanceToCameraThreshold	0	Distance from the entity to the selected camera
Qt3DRender::QLevelOfDetail::ProjectedScreenPixelSizeThreshold	1	Size of the entity when projected on the screen as seen from the selected camera, expressed in number of pixels on the side of the bounding square in screen space.

Member Function Documentation

QLevelOfDetail::QLevelOfDetail(Qt3DCore::QNode *parent = nullptr)

Constructs a new QLevelOfDetail with the specified parent.

[slot] void QLevelOfDetail::setCamera(Qt3DRender::QCamera *camera)

Sets the camera relative to which distance and size are computed.

Note: Setter function for property camera.

See also camera().

[slot] void QLevelOfDetail::setCurrentIndex(int currentIndex)

Sets the currentIndex.

Note: This should not normally be set by the user.

However, if the component is disabled, then changing the current index is a simple way of switching between multiple representations.

Note: Setter function for property currentIndex.

See also currentIndex().

[slot] void QLevelOfDetail::setThresholdType(Qt3DRender::QLevelOfDetail::ThresholdType thresholdType)

Sets the way thresholds values are interpreted with parameter thresholdType

Note: Setter function for property thresholdType.

See also thresholdType() and Qt3DRender::QLevelOfDetail::ThresholdType.

[slot] void QLevelOfDetail::setThresholds(const QVector<qreal> &thresholds)

Sets the range values in thresholds.

Note: Setter function for property thresholds.

See also thresholds() and Qt3DRender::QLevelOfDetail::thresholdType.