API Docs for:

QuadraticBezierCurve

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

Overview

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


Quadratic Bezier Curve from WikiPedia

Examples

Usage

Animation along a QuadraticBezierCurve

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

var curve = new xeogl.QuadraticBezierCurve({
    v0: [10, 0, 0],
    v1: [20, 15, 0],
    v2: [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 QuadraticBezierCurve'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 QuadraticBezierCurve'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

QuadraticBezierCurve

(
  • [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 QuadraticBezierCurve.

    • [v0=[0,0,0] optional

      The starting point.

    • [v1=[0,0,0] optional

      The middle control point.

    • [v2=[0,0,0] optional

      The end point.

    • [t=0] optional

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

Methods

create

(
  • [cfg]
)

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

The method is given a component configuration, like so:

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

Parameters:

  • [cfg] optional

    Configuration for the component instance.

Returns:

:

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 QuadraticBezierCurve at the given position.

Parameters:

  • t Number

    Position to get point at.

Returns:

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 Component/superTypes:property, 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.Mesh); // Returns false, because xeogl.Rotate does not (even indirectly) extend xeogl.Mesh

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

(
  • subId
)

Cancels an event subscription that was previously made with Component#on() or Component#once().

Parameters:

  • subId String

    Publication subId

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 subIdd.

This is equivalent to calling Component#on(), and then calling Component#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.

length

Number

Length of this Curve.

metadata

Object

Arbitrary, user-defined metadata on this component.

model

Model final

The Model which contains this Component, if any.

Will be null if this Component is not in a Model.

point

Array of Number

Point on this QuadraticBezierCurve at position t.

scene

Scene final

The parent Scene that contains this Component.

t

Number

Progress along this QuadraticBezierCurve.

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.

For example: "xeogl.AmbientLight", "xeogl.MetallicMaterial" etc.

v0

Float32Array

Starting point on this QuadraticBezierCurve.

Fires a v0 event on change.

Default: [0.0, 0.0, 0.0]

v1

Float32Array

Middle control point on this QuadraticBezierCurve.

Fires a v1 event on change.

Default: [0.0, 0.0, 0.0]

v2

Float32Array

End point on this QuadraticBezierCurve.

Fires a v2 event on change.

Default: [0.0, 0.0, 0.0]

Events

destroyed

Fired when this Component is destroyed.

t

Fired whenever this QuadraticBezierCurve's t property changes.

Event Payload:

  • value Object

    The property's new value

v0

Fired whenever this QuadraticBezierCurve's v0 property changes.

Event Payload:

  • value Object

    The property's new value

v1

Fired whenever this QuadraticBezierCurve's v1 property changes.

Event Payload:

  • value Object

    The property's new value

v2

Fired whenever this QuadraticBezierCurve's v2 property changes.

Event Payload:

  • value Object

    The property's new value