class 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¶

Properties¶

cameraᅟ
currentIndexᅟ
thresholdTypeᅟ
thresholdsᅟ
volumeOverrideᅟ

Methods¶

def __init__()
def camera()
def createBoundingSphere()
def currentIndex()
def thresholdType()
def thresholds()
def volumeOverride()

Signals¶

def cameraChanged()
def currentIndexChanged()
def thresholdTypeChanged()
def thresholdsChanged()
def volumeOverrideChanged()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

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 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.

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.

Note

Properties can be used directly when from __feature__ import true_property is used or via accessor functions otherwise.

property cameraᅟ: QCamera¶

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

Access functions:

camera()
setCamera()
Signal cameraChanged()

property currentIndexᅟ: int¶

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

Access functions:

currentIndex()
setCurrentIndex()
Signal currentIndexChanged()

property thresholdTypeᅟ: Qt3DRender.QLevelOfDetail.ThresholdType¶

Specifies how range values are interpreted.

See also

ThresholdType

Access functions:

thresholdType()
setThresholdType()
Signal thresholdTypeChanged()

property thresholdsᅟ: list of qreal¶

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

Access functions:

thresholds()
setThresholds()
Signal thresholdsChanged()

property volumeOverrideᅟ: 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

Access functions:

volumeOverride()
setVolumeOverride()
Signal volumeOverrideChanged()

__init__([parent=None])¶

Parameters:: parent – QNode

Constructs a new QLevelOfDetail with the specified parent.

camera()¶

Return type:: QCamera

See also

setCamera()

Getter of property cameraᅟ .

cameraChanged(camera)¶

Parameters:: camera – QCamera

Notification signal of property cameraᅟ .

createBoundingSphere(center, radius)¶

Parameters:

center – QVector3D
radius – float

Return type:

QLevelOfDetailBoundingSphere

currentIndex()¶

Return type:: int

See also

setCurrentIndex()

Getter of property currentIndexᅟ .

currentIndexChanged(currentIndex)¶

Parameters:: currentIndex – int

Notification signal of property currentIndexᅟ .

setCamera(camera)¶

Parameters:: camera – QCamera

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

See also

camera()

Setter of property cameraᅟ .

setCurrentIndex(currentIndex)¶

Parameters:: currentIndex – int

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.

See also

currentIndex()

Setter of property currentIndexᅟ .

setThresholdType(thresholdType)¶

Parameters:: thresholdType – ThresholdType

Sets the way thresholds values are interpreted with parameter thresholdType

See also

thresholdType() ThresholdType

Setter of property thresholdTypeᅟ .

setThresholds(thresholds)¶

Parameters:: thresholds – .list of qreal

Sets the range values in thresholds.

See also

thresholds() thresholdType

Setter of property thresholdsᅟ .

setVolumeOverride(volumeOverride)¶

Parameters:: volumeOverride – QLevelOfDetailBoundingSphere

See also

volumeOverride()

Setter of property volumeOverrideᅟ .

thresholdType()¶

Return type:: ThresholdType

See also

setThresholdType()

Getter of property thresholdTypeᅟ .

thresholdTypeChanged(thresholdType)¶

Parameters:: thresholdType – ThresholdType

Notification signal of property thresholdTypeᅟ .

thresholds()¶

Return type:: .list of qreal

See also

setThresholds()

Getter of property thresholdsᅟ .

thresholdsChanged(thresholds)¶

Parameters:: thresholds – .list of qreal

Notification signal of property thresholdsᅟ .

volumeOverride()¶

Return type:: QLevelOfDetailBoundingSphere

See also

setVolumeOverride()

Getter of property volumeOverrideᅟ .

volumeOverrideChanged(volumeOverride)¶

Parameters:: volumeOverride – QLevelOfDetailBoundingSphere

Notification signal of property volumeOverrideᅟ .