Qt3D Core

Core elements

The Core exposes a few default elements that make up all Qt3D scenes.

Node

A base Qt3D element.

Entity

An Entity is a Node which has a list of Component properties. This is the type of elements that are actually rendered.

Component

Components are elements that are used to further specify an Entity.

Transformations

• Transform

A Component that contains a list of transformation

Transform {
 id : transform_0
 Rotate {
 axis : Qt.vector3d(0,1,0)
 angle : 30
 }
 Scale {
 scale3D : Qt.vector3d(0.5, 0.25, 0.5)
 }
 Translate {
 dx : –9; dy : 2; dz : 20
 }
 }

• LookAtTransform

Performs a LookAtTransform.

• MatrixTransform

Performs a transformation based on the Matrix provided.

• TranslateTransform

Performs a translation.

• RotateTransform

Performs a rotation around an axis.

• ScaleTransform

Performs a scaling.

Others Components

• CameraLens

Contains the lens properties of a Camera.

' Projection Type ' Far plane ' Near plane ' Field of view ' Aspect ratio =====

Custom elements

Custom elements can be created by subclassing an Entity and predefining a set of properties.

• Camera

The Camera elements is an Entity that contains a Transform and a CameraLens.

Camera {
 id : camera2 =====

lens : CameraLens {
 projectionType: CameraLens.PerspectiveProjection
 fieldOfView: 45
 aspectRatio: 16/9
 nearPlane : 0.01
 farPlane : 1000.0
 }

transform : Transform {
 LookAt {
 position: Qt.vector3d( 0.0, –1.0, –5.0 )
 upVector: Qt.vector3d( 0.0, 1.0, 0.0 )
 viewCenter: Qt.vector3d( 0.0, 2.0, 10.0 )
 }
 Rotate {
 axis : Qt.vector3d(0, 0, 1)
 angle : 40
 }
 }
 }

Resources Management

To achieve high rendering performances, the memory access to the resources has to be properly managed and structured. Therefore, a set of templated resources management oriented classes have been developed in the core of Qt3D.

• QHandle
• QArrayResourcesManager
• QListResourcesManager

The use of a Handle systems allows for resources to be easily accessed and managed while allowing for memory structure to be realigned so as to maintain a contiguous memory alignment and reduce fragmentation. This should lower the amount of cache misses and speed up rendering.

Other Resources management oriented classes include :

• QCircularBuffer