- Qt 6.9
- Qt Quick 3D
- QML Types
- Loader3D
- Qt Quick 3D | Commercial or GPLv3

# Loader3D QML Type

Allows dynamic loading of a 3D subtree from a URL or Component. More...

Import Statement: | `import QtQuick3D`
Inherits: | Node

- List of all members, including inherited members

## Properties

- active : bool
- asynchronous : bool
- item : object
- progress : real
- source : url
- sourceComponent : Component
- status : enumeration

## Signals

- loaded()

## Methods

- object setSource(url source, object properties)

## Detailed Description

Loader3D is used to dynamically load QML components for Qt Quick 3D.

Loader3D can load a QML file (using the source property) or a Component object (using the sourceComponent property). It is useful for delaying the creation of a component until it is required: for example, when a component should be created on demand, or when a component should not be created unnecessarily for performance reasons.

Note: Loader3D works the same way as Loader. The difference between the two is that Loader provides a way to dynamically load objects that inherit Item, whereas Loader3D provides a way to load objects that inherit Object3D and is part of a 3D scene.

## Property Documentation

active : bool

This property is `true` if the Loader3D is currently active. The default value for this property is `true`.

If the Loader3D is inactive, changing the source or sourceComponent will not cause the item to be instantiated until the Loader3D is made active.

Setting the value to inactive will cause any item loaded by the loader to be released, but will not affect the source or sourceComponent.

The status of an inactive loader is always `Null`.

See also source and sourceComponent.

asynchronous : bool

This property holds whether the component will be instantiated asynchronously. By default it is `false`.

When used in conjunction with the source property, loading and compilation will also be performed in a background thread.

Loading asynchronously creates the objects declared by the component across multiple frames, and reduces the likelihood of glitches in animation. When loading asynchronously the status will change to Loader3D.Loading. Once the entire component has been created, the item will be available and the status will change to Loader.Ready.

Changing the value of this property to `false` while an asynchronous load is in progress will force immediate, synchronous completion. This allows beginning an asynchronous load and then forcing completion if the Loader3D content must be accessed before the asynchronous load has completed.

To avoid seeing the items loading progressively set `visible` appropriately, e.g.

     Loader3D {
         source: "mycomponent.qml"
         asynchronous: true
         visible: status == Loader3D.Ready
     }

Note that this property affects object instantiation only; it is unrelated to loading a component asynchronously via a network.

item : object `[read-only]`

This property holds the top-level object that is currently loaded.

progress : real `[read-only]`

This property holds the progress of loading QML data from the network, from 0.0 (nothing loaded) to 1.0 (finished). Most QML files are quite small, so this value will rapidly change from 0 to 1.

See also status.

source : url

This property holds the URL of the QML component to instantiate.

To unload the currently loaded object, set this property to an empty string, or set sourceComponent to `undefined`. Setting `source` to a new URL will also cause the item created by the previous URL to be unloaded.

See also sourceComponent, status, and progress.

sourceComponent : Component

This property holds the Component to instantiate.

     Item {
         Component {
             id: redCube
             Model {
                 source: "#Cube"
                 materials: DefaultMaterial {
                     diffuseColor: "red"
                 }
             }
         }

         Loader3D { sourceComponent: redCube }
         Loader3D { sourceComponent: redCube; x: 10 }
     }

To unload the currently loaded object, set this property to `undefined`.

See also source and progress.

status : enumeration `[read-only]`

This property holds the status of QML loading. It can be one of:

Constant | Description
--- | ---
`Loader3D.Null` | The loader is inactive or no QML source has been set.
`Loader3D.Ready` | The QML source has been loaded.
`Loader3D.Loading` | The QML source is currently being loaded.
`Loader3D.Error` | An error occurred while loading the QML source.

Use this status to provide an update or respond to the status change in some way. For example, you could:

- Trigger a state change:

       State { name: 'loaded'; when: loader.status == Loader3D.Ready }

- Implement an `onStatusChanged` signal handler:

       Loader3D {
           id: loader
           onStatusChanged: if (loader.status == Loader3D.Ready) console.log('Loaded')
       }

- Bind to the status value:

       Text { text: loader.status == Loader3D.Ready ? 'Loaded' : 'Not loaded' }

Note that if the source is a local file, the status will initially be Ready (or Error). While there will be no onStatusChanged signal in that case, the onLoaded will still be invoked.

See also progress.

## Signal Documentation

loaded()

This signal is emitted when the status becomes `Loader3D.Ready`, or on successful initial load.

The corresponding handler is `onLoaded`.

Note: The corresponding handler is `onLoaded`.

## Method Documentation

object setSource(url source, object properties)

Creates an object instance of the given source component that will have the given properties. The properties argument is optional. The instance will be accessible via the item property once loading and instantiation is complete.

If the active property is `false` at the time when this function is called, the given source component will not be loaded but the source and initial properties will be cached. When the loader is made active, an instance of the source component will be created with the initial properties set.

Setting the initial property values of an instance of a component in this manner will not trigger any associated Behaviors.

Note that the cached properties will be cleared if the source or sourceComponent is changed after calling this function but prior to setting the loader active.

See also source and active.