xeogl / API Docs

API Docs for: 1.0.0

CubicBezierCurve

Extends Curve
Module: curves
Parent Module: xeogl

A CubicBezierCurve is a Curve along which a 3D position can be animated.

Overview

• As shown in the diagram below, a CubicBezierCurve is defined by four control points.
• You can sample a point and a CubicBezierCurve/tangent:property vector on a CubicBezierCurve for any given value of t in the range [0..1].
• When you set t on a CubicBezierCurve, its point and CubicBezierCurve/tangent:property properties will update accordingly.
• To build a complex path, you can combine an unlimited combination of CubicBezierCurves, QuadraticBezierCurves and SplineCurves into a Path.

Usage

Animation along a CubicBezierCurve

Let's create a CubicBezierCurve, subscribe to updates on its point, tangent and t properties, then vary its t property over time:

``````var curve = new xeogl.CubicBezierCurve({
v0: [-10, 0, 0],
v1: [-5, 15, 0],
v2: [20, 15, 0],
v3: [10, 0, 0]
});

curve.on("point", function(point) {
this.log("curve.point=" + JSON.stringify(point));
});

curve.on("tangent", function(tangent) {
this.log("curve.tangent=" + JSON.stringify(tangent));
});

curve.on("t", function(t) {
this.log("curve.t=" + t);
});

curve.scene.on("tick", function(e) {
curve.t = (e.time - e.startTime) * 0.01;
});
``````

Randomly sampling points

Use CubicBezierCurve's getPoint and getTangent methods to sample the point and vector at a given t:

``````curve.scene.on("tick", function(e) {

var t = (e.time - e.startTime) * 0.01;

var point = curve.getPoint(t);
var tangent = curve.getTangent(t);

this.log("t=" + t + ", point=" + JSON.stringify(point) + ", tangent=" + JSON.stringify(tangent));
});
``````

Sampling multiple points

Use CubicBezierCurve's getPoints method to sample a list of equidistant points along it. In the snippet below, we'll build a Geometry that renders a line along the curve. Note that we need to flatten the points array for consumption by the Geometry.

``````var geometry = new xeogl.Geometry({
positions: xeogl.math.flatten(curve.getPoints(50))
});
``````

Constructor

`CubicBezierCurve`

(
• `[scene]`
• `[cfg]`
)

Parameters:

• `[scene]` Scene optional

Parent Scene.

• `[cfg]` optional

Configuration

• `[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 CubicBezierCurve.

• `[v0=[0,0,0]]` optional

The starting point.

• `[v1=[0,0,0]]` optional

The first control point.

• `[v2=[0,0,0]]` optional

The middle control point.

• `[v3=[0,0,0]]` optional

The ending point.

• `[t=0]` optional

Current position on this CubicBezierCurve, in range between 0..1.

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

`getPoint`

(
• `t`
)
Array of Number

Returns point on this CubicBezierCurve at the given position.

Parameters:

• `t` Number

Position to get point at.

Array of Number:

}

`getPoints`

(
• `divisions`
)
Array of Array

Samples points on this Curve, at the given number of equally-spaced divisions.

Parameters:

• `divisions` Number

The number of divisions.

Returns:

Array of Array:

Array of sampled 3D points.

`getTangent`

(
• `t`
)
Array of Number

Returns a normalized tangent vector on this Curve at the given position.

Parameters:

• `t` Number

Position to get tangent at.

Returns:

Array of Number:

} Normalized tangent vector

`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

`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.

`length`

Number

Length of this Curve.

`metadata`

Object

Arbitrary, user-defined metadata on this component.

`point`

Array of Number

Point on this CubicBezierCurve at position t.

`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.

`t`

Number

Current position of progress along this CubicBezierCurve.

Automatically clamps to range [0..1].

Fires a t event on change.

Default: 0

`tangent`

Array of Number

Tangent on this Curve at position t.

`type`

String final

JavaScript class name for this Component.

`v0`

Float32Array

Starting point on this CubicBezierCurve.

Fires a v0 event on change.

Default: [0.0, 0.0, 0.0]

`v1`

Float32Array

First control point on this CubicBezierCurve.

Fires a v1 event on change.

Default: [0.0, 0.0, 0.0]

`v2`

Float32Array

Second control point on this CubicBezierCurve.

Fires a v2 event on change.

Default: [0.0, 0.0, 0.0]

`v3`

Float32Array

End point on this CubicBezierCurve.

Fires a v3 event on change.

Default: [0.0, 0.0, 0.0]

Events

`destroyed`

Fired when this Component is destroyed.

`t`

Fired whenever this CubicBezierCurve's t property changes.

• `value` Object

The property's new value

`v0`

Fired whenever this CubicBezierCurve's v0 property changes.

• `value` Object

The property's new value

`v1`

Fired whenever this CubicBezierCurve's v1 property changes.

• `value` Object

The property's new value

`v2`

Fired whenever this CubicBezierCurve's v2 property changes.

• `value` Object

The property's new value

`v3`

Fired whenever this CubicBezierCurve's v3 property changes.

• `value` Object