QLevelOfDetail

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

Inherited by: QLevelOfDetailSwitch

Synopsis

Functions

• def camera ()

• def createBoundingSphere (center, radius)

• def currentIndex ()

• def thresholdType ()

• def thresholds ()

• def volumeOverride ()

Slots

• def setCamera (camera)

• def setCurrentIndex (currentIndex)

• def setThresholdType (thresholdType)

• def setThresholds (thresholds)

• def setVolumeOverride (volumeOverride)

Signals

• def cameraChanged (camera)

• def currentIndexChanged (currentIndex)

• def thresholdTypeChanged (thresholdType)

• def thresholdsChanged (thresholds)

• def volumeOverrideChanged (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);
QList<qreal> thresholds = {20, 35, 50, 65};
lod->setThresholds(thresholds);
lod->setCamera(mainCamera);
renderableEntity->addComponent(lod);

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

class PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail([parent=None])

Parameters

parent – PySide6.Qt3DCore.Qt3DCore.QNode

Constructs a new QLevelOfDetail with the specified parent.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.ThresholdType

Specifies how the values in the thresholds are interpreted

Constant	Description
Qt3DRender.QLevelOfDetail.DistanceToCameraThreshold	Distance from the entity to the selected camera
Qt3DRender.QLevelOfDetail.ProjectedScreenPixelSizeThreshold	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.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.camera()

Return type

PySide6.Qt3DRender.Qt3DRender.QCamera

Holds the id of the camera that is used to compute the actual distance or the screen size.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.cameraChanged(camera)

Parameters

camera – PySide6.Qt3DRender.Qt3DRender.QCamera

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.createBoundingSphere(center, radius)

Parameters

• center – PySide6.QtGui.QVector3D

• radius – float

Return type

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetailBoundingSphere

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.currentIndex()

Return type

int

The index in the range array which matches the current distance to the camera or screen size.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.currentIndexChanged(currentIndex)

Parameters

currentIndex – int

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.setCamera(camera)

Parameters

camera – PySide6.Qt3DRender.Qt3DRender.QCamera

Holds the id of the camera that is used to compute the actual distance or the screen size.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.setCurrentIndex(currentIndex)

Parameters

currentIndex – int

The index in the range array which matches the current distance to the camera or screen size.

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.setThresholdType(thresholdType)

Parameters

thresholdType – ThresholdType

Specifies how range values are interpreted.

See also

ThresholdType

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.setThresholds(thresholds)

Parameters

thresholds –

Array of range values as float point numbers. The value for the most detailed representation should be specified first.

If thresholdType is set to DistanceToCameraThreshold , values should be specified in ascending order, in camera space coordinates

If thresholdType is set to ProjectedScreenPixelSizeThreshold , values should be specified in descending order, in screen space pixels.

See also

ThresholdType

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.setVolumeOverride(volumeOverride)

Parameters

volumeOverride – PySide6.Qt3DRender.Qt3DRender.QLevelOfDetailBoundingSphere

The default is a sphere of radius 1 and centered at the local origin of the entity. This proxy volume is used to compute the distance to the camera or the size of the screen projection.

If this value to nullptr, the bounding volume of the entity is used. Care must be taken that this bounding volume never becomes invalid.

See also

QLevelOfDetailBoundingSphere

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.thresholdType()

Return type

ThresholdType

Specifies how range values are interpreted.

See also

ThresholdType

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.thresholdTypeChanged(thresholdType)

Parameters

thresholdType – ThresholdType

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.thresholds()

Return type

Array of range values as float point numbers. The value for the most detailed representation should be specified first.

If thresholdType is set to DistanceToCameraThreshold , values should be specified in ascending order, in camera space coordinates

If thresholdType is set to ProjectedScreenPixelSizeThreshold , values should be specified in descending order, in screen space pixels.

See also

ThresholdType

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.thresholdsChanged(thresholds)

Parameters

thresholds –

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.volumeOverride()

Return type

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetailBoundingSphere

The default is a sphere of radius 1 and centered at the local origin of the entity. This proxy volume is used to compute the distance to the camera or the size of the screen projection.

If this value to nullptr, the bounding volume of the entity is used. Care must be taken that this bounding volume never becomes invalid.

See also

QLevelOfDetailBoundingSphere

PySide6.Qt3DRender.Qt3DRender.QLevelOfDetail.volumeOverrideChanged(volumeOverride)

Parameters

volumeOverride – PySide6.Qt3DRender.Qt3DRender.QLevelOfDetailBoundingSphere