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Qt3D Core

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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.

2poe3bn.png

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