## Phaser. Hermite

#### new Hermite(p1x, p1y, p2x, p2y, v1x, v1y, v2x, v2y, accuracy)

A data representation of a Hermite Curve (see http://en.wikipedia.org/wiki/Cubic_Hermite_spline)

A Hermite curve has a start and end point and tangent vectors for both of them.
The curve will always pass through the two control points and the shape of it is controlled
by the length and direction of the tangent vectors. At the control points the curve will
be facing exactly in the vector direction.

As these curves change speed (speed = distance between points separated by an equal change in
't' value - see Hermite.getPoint) this class attempts to reduce the variation by pre-calculating
the `accuracy` number of points on the curve. The straight-line distances to these points are stored
in the private 'points' array, and this information is used by Hermite.findT() to convert a pixel
distance along the curve into a 'time' value.

Higher `accuracy` values will result in more even movement, but require more memory for the points
list. 5 works, but 10 seems to be an ideal value for the length of curves found in most games on
a desktop screen. If you use very long curves (more than 400 pixels) you may need to increase
this value further.

##### Parameters:
Name Type Argument Default Description
`p1x` number

The x coordinate of the start of the curve.

`p1y` number

The y coordinate of the start of the curve.

`p2x` number

The x coordinate of the end of the curve.

`p2y` number

The y coordinate of the end of the curve.

`v1x` number

The x component of the tangent vector for the start of the curve.

`v1y` number

The y component of the tangent vector for the start of the curve.

`v2x` number

The x component of the tangent vector for the end of the curve.

`v2y` number

The y component of the tangent vector for the end of the curve.

`accuracy` number <optional>
10

The amount of points to pre-calculate on the curve.

Source - geom/Hermite.js, line 39

### Members

#### accuracy :number

The amount of points to pre-calculate on the curve.

Source - geom/Hermite.js, line 396

#### p1x :number

The x coordinate of the start of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 420

#### p1y :number

The y coordinate of the start of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 444

#### p2x :number

The x coordinate of the end of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 468

#### p2y :number

The y coordinate of the end of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 492

#### v1x :number

The x component of the tangent vector for the start of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 516

#### v1y :number

The y component of the tangent vector for the start of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 540

#### v2x :number

The x component of the tangent vector for the end of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 564

#### v2y :number

The y component of the tangent vector for the end of the curve. Setting this value will recalculate the curve.

Source - geom/Hermite.js, line 588

### Methods

#### calculateEvenPoints() → {number}

Calculate a number of points along the curve, based on `Hermite.accuracy`, and stores them in the private `_points` array.

##### Returns:
number -

The total length of the curve approximated as straight line distances between the points.

Source - geom/Hermite.js, line 146

#### findT(distance) → {number}

Convert a distance along this curve into a `time` value which will be between 0 and 1.

For example if this curve has a length of 100 pixels then `findT(50)` would return `0.5`.

##### Parameters:
Name Type Description
`distance` integer

The distance into the curve in pixels. Should be a positive integer.

##### Returns:
number -

The time (`t`) value, a float between 0 and 1.

Source - geom/Hermite.js, line 173

#### getAngle(t) → {number}

Calculate and return the angle, in radians, of the curves tangent based on time.

##### Parameters:
Name Type Argument Default Description
`t` number <optional>
0

The `t` (time) value at which to find the angle. Must be between 0 and 1.

##### Returns:
number -

The angle of the line at the specified `t` time value along the curve. The value is in radians.

Source - geom/Hermite.js, line 336

#### getAngleWithDistance(distance) → {number}

Calculate and return the angle, in radians, of the curves tangent at the given pixel distance along the curves length.

##### Parameters:
Name Type Argument Default Description
`distance` number <optional>
0

The distance along the curve to get the angle from, in pixels.

##### Returns:
number -

The angle of the line at the specified distance along the curve. The value is in radians.

Source - geom/Hermite.js, line 354

#### getEntryTangent(point) → {Phaser.Point}

Get the angle of the curves entry point.

##### Parameters:
Name Type Description
`point` Phaser.Point | Object

The Phaser.Point object, or an Object with public `x` and `y` properties, in which the tangent vector values will be stored.

##### Returns:

A Point object containing the tangent vector of this Hermite curve.

Source - geom/Hermite.js, line 376

#### getPoint(t, point) → {Phaser.Point}

Get a point on the curve using the `t` (time) value, which must be between 0 and 1.

##### Parameters:
Name Type Argument Default Description
`t` number <optional>
0

The time value along the curve from which to extract a point. This is a value between 0 and 1, where 0 represents the start of the curve and 1 the end.

`point` Phaser.Point | Object <optional>

An optional Phaser.Point, or Object containing public `x` and `y` properties. If given the resulting values will be stored in the Objects `x` and `y` properties. If omitted a new Phaser.Point object is created.

##### Returns:

An Object with the x, y coordinate of the curve at the specified `t` value set in its `x` and `y` properties.

Source - geom/Hermite.js, line 276

#### getPointWithDistance(distance, point) → {Phaser.Point}

Get a point on the curve using the distance, in pixels, along the curve.

##### Parameters:
Name Type Argument Default Description
`distance` integer <optional>
0

The distance along the curve to get the point from, given in pixels.

`point` Phaser.Point | Object <optional>

An optional Phaser.Point, or Object containing public `x` and `y` properties. If given the resulting values will be stored in the Objects `x` and `y` properties. If omitted a new Phaser.Point object is created.

##### Returns:

The point on the line at the specified 'distance' along the curve.

Source - geom/Hermite.js, line 309

#### getX(t) → {number}

Get the X component of a point on the curve based on the `t` (time) value, which must be between 0 and 1.

##### Parameters:
Name Type Argument Default Description
`t` number <optional>
0

The time value along the curve from which to extract a point. This is a value between 0 and 1, where 0 represents the start of the curve and 1 the end.

##### Returns:
number -

The X component of a point on the curve based on the `t` (time) value.

Source - geom/Hermite.js, line 210

#### getY(t) → {number}

Get the Y component of a point on the curve based on the `t` (time) value, which must be between 0 and 1.

##### Parameters:
Name Type Argument Default Description
`t` number <optional>
0

The time value along the curve from which to extract a point. This is a value between 0 and 1, where 0 represents the start of the curve and 1 the end.

##### Returns:
number -

The Y component of a point on the curve based on the `t` (time) value.

Source - geom/Hermite.js, line 243

#### recalculate() → {Phaser.Hermite}

Performs the curve calculations.

This is called automatically if you change any of the curves public properties, such as `Hermite.p1x` or `Hermite.v2y`.

If you adjust any of the internal private values, then call this to update the points.

##### Returns:

This object.

Source - geom/Hermite.js, line 123
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