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