# xeogl / API Docs

API Docs for: 1.0.0

# Quaternion

Extends Transform
Module: transforms
Parent Module: xeogl

A Quaternion is a Transform that rotates associated Entities or Models.

## Overview

• Instances of Transform and its sub-classes may be connected into hierarchies.
• When an Entity or Model is connected to a leaf Transform within a Transform hierarchy, it will be transformed by each Transform on the path up to the root, in that order.

## Usage

In this example we have two Entities that are transformed by a hierarchy that contains Quaternion, Translate and Scale transforms. The Entities share the same BoxGeometry.

``````var quaternion = new xeogl.Quaternion({
xyzw: [0, 0, 0, 1], // Unit quaternion
});

var translate1 = new xeogl.Translate({
parent: quaternion,
xyz: [-5, 0, 0] // Translate along -X axis
});

var translate2 = new xeogl.Translate({
parent: quaternion,
xyz: [5, 0, 0] // Translate along +X axis
});

var scale = new xeogl.Scale({
parent: translate2,
xyz: [1, 2, 1] // Scale x2 on Y axis
});

var geometry = new xeogl.BoxGeometry();

var entity1 = new xeogl.Entity(scene, {
transform: translate1,
geometry: geometry
});

var entity2 = new xeogl.Entity({
transform: scale,
geometry: geometry
});
``````

Since everything in xeogl is dynamically editable, we can restructure the transform hierarchy at any time.

Let's insert a Scale between the first Translate and the first Entity:

``````var scale2 = new xeogl.Scale({
parent: translate1,
xyz: [1, 1, 2] // Scale x2 on Z axis
});

Entity2.transform = scale2;
``````

Let's spin the Quaternion:

``````// Rotate 0.2 degrees about Y-axis on each frame
scene.on("tick", function(e) {
quaternion.rotate([0, 1, 0, 0.2]);
});
``````

## Constructor

### `Quaternion`

(
• `[scene]`
• `[cfg]`
)

#### Parameters:

• `[scene]` Scene optional

Parent Scene - creates this Quaternion in the default Scene when omitted.

• `[cfg]` optional

Configs

• `[id]` String optional

Optional ID, unique among all components in the parent scene, generated automatically when omitted.

• `[meta]` String:Object optional

Optional map of user-defined metadata to attach to this Quaternion.

• `[parent]` String | Transform optional

ID or instance of a parent Transform within the same Scene.

• `[xyzw=[0,0,0,1]]` Array(Number) optional

The initial Quaternion elements.

## Methods

### `create`

(
• `[cfg]`
• `[instanceId]`
)

Convenience method for creating a Component within this Component's Scene.

You would typically use this method to conveniently instantiate components that you'd want to share (ie. "instance") among your Entities.

The method is given a component type, configuration and optional instance ID, like so:

``````var material = myComponent.create({
type: "xeogl.PhongMaterial",
diffuse: [1,0,0],
specular: [1,1,0]
}, "myMaterial");
``````

The first time you call this method for the given `type` and `instanceId`, this method will create the PhongMaterial, passing the given attributes to the component's constructor.

If you call this method again, specifying the same `type` and `instanceId`, the method will return the same component instance that it returned the first time, and will ignore the new configuration:

``````var material2 = component.create({ type: "xeogl.PhongMaterial", specular: [1,1,0] }, "myMaterial");
``````

So in this example, our PhongMaterial will continue to have the red specular and diffuse color that we specified the first time.

Each time you call this method with the same `type` and `instanceId`, the Scene will internally increment a reference count for the component instance.

#### Parameters:

• `[cfg]` optional

Configuration for the component instance - only used if this is the first time you are getting the component, ignored when reusing an existing instance.

• `[instanceId]` String | Number optional

Identifies the shared component instance. Note that this is not used as the ID of the component - you can specify the component ID in the `cfg` parameter.

:

### `destroy`

()

Destroys this component.

Fires a destroyed event on this Component.

Automatically disassociates this component from other components, causing them to fall back on any defaults that this component overrode on them.

TODO: describe effect with respect to #create

### `error`

(
• `message`
)

Logs an error for this component to the JavaScript console.

The console message will have this format: `[ERROR] [<component type> =<component id>: <message>`

Also fires the message as an error event on the parent Scene.

#### Parameters:

• `message` String

The message to log

### `fire`

(
• `event`
• `value`
• `[forget=false]`
)

Fires an event on this component.

Notifies existing subscribers to the event, optionally retains the event to give to any subsequent notifications on the event as they are made.

#### Parameters:

• `event` String

The event type name

• `value` Object

The event parameters

• `[forget=false]` Boolean optional

When true, does not retain for subsequent subscribers

### `hasSubs`

(
• `event`
)
Boolean

Returns true if there are any subscribers to the given event on this component.

#### Parameters:

• `event` String

The event

#### Returns:

Boolean:

True if there are any subscribers to the given event on this component.

### `isType`

(
• `type`
)
Boolean

Tests if this component is of the given type, or is a subclass of the given type.

The type may be given as either a string or a component constructor.

This method works by walking up the inheritance type chain, which this component provides in property superTypes, returning true as soon as one of the type strings in the chain matches the given type, of false if none match.

#### Examples:

``````var myRotate = new xeogl.Rotate({ ... });

myRotate.isType(xeogl.Component); // Returns true for all xeogl components
myRotate.isType("xeogl.Component"); // Returns true for all xeogl components
myRotate.isType(xeogl.Rotate); // Returns true
myRotate.isType(xeogl.Transform); // Returns true
myRotate.isType("xeogl.Transform"); // Returns true
myRotate.isType(xeogl.Entity); // Returns false, because xeogl.Rotate does not (even indirectly) extend xeogl.Entity
``````

#### Parameters:

• `type` String | Function

Component type to compare with, eg "xeogl.PhongMaterial", or a xeogl component constructor.

#### Returns:

Boolean:

True if this component is of given type or is subclass of the given type.

### `log`

(
• `message`
)

Logs a console debugging message for this component.

The console message will have this format: `[LOG] [<component type> <component id>: <message>`

Also fires the message as a log event on the parent Scene.

#### Parameters:

• `message` String

The message to log

### `off`

(
• `handle`
)

Cancels an event subscription that was previously made with on or once.

#### Parameters:

• `handle` String

Publication handle

### `on`

(
• `event`
• `callback`
• `[scope=this]`
)
String

Subscribes to an event on this component.

The callback is be called with this component as scope.

#### Parameters:

• `event` String

The event

• `callback` Function

Called fired on the event

• `[scope=this]` Object optional

Scope for the callback

#### Returns:

String:

Handle to the subscription, which may be used to unsubscribe with {@link #off}.

### `once`

(
• `event`
• `callback`
• `[scope=this]`
)

Subscribes to the next occurrence of the given event, then un-subscribes as soon as the event is handled.

This is equivalent to calling on, and then calling off inside the callback function.

#### Parameters:

• `event` String

Data event to listen to

• `callback` Function(data)

Called when fresh data is available at the event

• `[scope=this]` Object optional

Scope for the callback

### `rotate`

(
• `angleAxis`
)

Rotates this Quaternion. Fires an xyzw event to notify of update to the Quaternion elements.

#### Parameters:

• `angleAxis` Float32Array

Rotation in angle-axis form.

### `warn`

(
• `message`
)

Logs a warning for this component to the JavaScript console.

The console message will have this format: `[WARN] [<component type> =<component id>: <message>`

Also fires the message as a warn event on the parent Scene.

#### Parameters:

• `message` String

The message to log

## Properties

### `destroyed`

Boolean

True as soon as this Component has been destroyed

### `id`

String final

Unique ID for this Component within its parent Scene.

### `isDefault`

Boolean

Indicates whether this is one of the Scene's built-in Components.

### `json`

JSON final

JSON object containing the state of this Component.

### `matrix`

Float32Array

The Transform's local matrix.

Fires a matrix event on change.

Default: [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1]

### `metadata`

Object

Arbitrary, user-defined metadata on this component.

### `parent`

Transform

The parent Transform.

Fires a parent event on change.

### `postMultiply`

Boolean

Flag that indicates whether this Transform is post-multiplied (default) or pre-multiplied by its parent Transform.

Fires an postMultiply event on change.

Default: true

### `scene`

Scene final

The parent Scene that contains this Component.

### `string`

String final

Inherited from Component but overwritten in `src/component.js:1065`

String containing the serialized JSON state of this Component.

### `superTypes`

Array of String final

An array of strings that indicates the chain of super-types within this component's inheritance hierarchy.

For example, if this component is a Rotate, which extends Transform, which in turn extends Component, then this property will have the value:

``````["xeogl.Component", "xeogl.Transform"]
``````

Note that the chain is ordered downwards in the hierarchy, ie. from super-class down towards sub-class.

### `type`

String final

JavaScript class name for this Component.

This is used when loading Scenes from JSON, and is included in the JSON representation of this Component, so that this class may be instantiated when loading it from the JSON representation.

For example: "xeogl.AmbientLight", "xeogl.ColorTarget", "xeogl.Lights" etc.

### `xyzw`

Float32Array

The quaternion elements. Fires an xyzw event on change.

Default: [0,0,0,1]

## Events

### `destroyed`

Fired when this Component is destroyed.

### `matrix`

Fired whenever this Transform's matrix property changes.

• `value` Object

The property's new value

### `parent`

Fired whenever this Transform's parent property changes.

• `value` Object

The property's new value

### `postMultiply`

Fired whenever this Transform's postMultiply property changes.

• `value` Object

The property's new value

### `updated`

Fired whenever this Transform's Transform/leafMatrix:property property changes.

This event does not carry the updated property value. Instead, subscribers will need to read that property again to get its updated value (which may be lazy-computed then).

### `xyzw`

Fired whenever this Quaternion's xyzw property changes.

• `value` Float32Array