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
- Tweening position along a QuadraticBezierCurve
- Tweening color along a QuadraticBezierCurve
- Path example
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 optionalParent Scene.
-
[cfg]optionalConfiguration
-
[id]String optionalOptional ID, unique among all components in the parent Scene, generated automatically when omitted.
-
[meta]String:Object optionalOptional map of user-defined metadata to attach to this QuadraticBezierCurve.
-
[v0=[0,0,0]optionalThe starting point.
-
[v1=[0,0,0]optionalThe middle control point.
-
[v2=[0,0,0]optionalThe end point.
-
[t=0]optionalCurrent position on this QuadraticBezierCurve, in range between 0..1.
-
Index
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]optionalConfiguration 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:
-
messageStringThe 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:
-
eventStringThe event type name
-
valueObjectThe event parameters
-
[forget=false]Boolean optionalWhen true, does not retain for subsequent subscribers
getPoint
-
t
Returns point on this QuadraticBezierCurve at the given position.
Parameters:
-
tNumberPosition to get point at.
Returns:
}
getPoints
-
divisions
Samples points on this Curve, at the given number of equally-spaced divisions.
Parameters:
-
divisionsNumberThe number of divisions.
Returns:
Array of sampled 3D points.
getTangent
-
t
Returns a normalized tangent vector on this Curve at the given position.
Parameters:
-
tNumberPosition to get tangent at.
Returns:
} Normalized tangent vector
hasSubs
-
event
Returns true if there are any subscribers to the given event on this component.
Parameters:
-
eventStringThe event
Returns:
True if there are any subscribers to the given event on this component.
isType
-
type
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.MeshParameters:
-
typeString | FunctionComponent type to compare with, eg "xeogl.PhongMaterial", or a xeogl component constructor.
Returns:
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>
Parameters:
-
messageStringThe message to log
off
-
subId
Cancels an event subscription that was previously made with Component#on() or Component#once().
Parameters:
-
subIdStringPublication subId
on
-
event -
callback -
[scope=this]
Subscribes to an event on this component.
The callback is be called with this component as scope.
Parameters:
-
eventStringThe event
-
callbackFunctionCalled fired on the event
-
[scope=this]Object optionalScope for the callback
Returns:
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:
-
eventStringData event to listen to
-
callbackFunction(data)Called when fresh data is available at the event
-
[scope=this]Object optionalScope for the callback
Properties
destroyed
Boolean
True as soon as this Component has been destroyed
length
Number
Length of this Curve.
model
Model
final
The Model which contains this Component, if any.
Will be null if this Component is not in a Model.
t
Number
Progress along this QuadraticBezierCurve.
Automatically clamps to range [0..1].
Fires a t event on change.
Default: 0
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:
-
valueObjectThe property's new value
v0
Fired whenever this QuadraticBezierCurve's v0 property changes.
Event Payload:
-
valueObjectThe property's new value