四元数（[name]）

该类实现了 [link:http://en.wikipedia.org/wiki/Quaternion quaternion] 。
四元数在three.js中用于表示 [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotation] （旋转）。

代码示例


		const quaternion = new THREE.Quaternion();
		quaternion.setFromAxisAngle( new THREE.Vector3( 0, 1, 0 ), Math.PI / 2 );

		const vector = new THREE.Vector3( 1, 0, 0 );
		vector.applyQuaternion( quaternion );

构造函数

[name]( [param:Float x], [param:Float y], [param:Float z], [param:Float w] )

[page:Float x] - x 坐标
[page:Float y] - y 坐标
[page:Float z] - z 坐标
[page:Float w] - w 坐标

属性

[property:Float x]

[property:Float y]

[property:Float z]

[property:Float w]

方法

[method:Float angleTo]( [param:Quaternion q] )

以弧度返回该四元数与四元数 [page:Quaternion q] 之间的夹角。

[method:Quaternion clone]()

创建一个与该四元数具有相同[page:.x x]、[page:.y y]、[page:.z z]和[page:.w w] 属性的四元数。

[method:Quaternion conjugate]()

返回该四元数的旋转共轭。四元数的共轭表示的是，围绕旋转轴在相反方向上的相同旋转。

[method:Quaternion copy]( [param:Quaternion q] )

复制四元数 [page:Quaternion q] 的 [page:.x x]、[page:.y y]、[page:.z z] 和 [page:.w w] 属性到该四元数中。

[method:Boolean equals]( [param:Quaternion v] )

[page:Quaternion v] - 用于进行比较的四元数。

将四元数 [page:Quaternion v] 的 [page:.x x]、 [page:.y y]、 [page:.z z] 和 [page:.w w] 的属性与当前四元数的对应属性相比较，以确定它们是否表示相同的旋转。

[method:Float dot]( [param:Quaternion v] )

计算四元数 [page:Quaternion v] 与当前四元数的[link:https://en.wikipedia.org/wiki/Dot_product dot product]（点积）。

[method:Quaternion fromArray]( [param:Array array], [param:Integer offset] )

[page:Array array] - 用于构造四元数的形如(x, y, z, w)的数组。
[page:Integer offset] - （可选）数组的偏移量。（译者注：使用数组中从第offset元素算起的四个元素）

从一个数组来设置四元数的 [page:.x x]、 [page:.y y]、[page:.z z] 和 [page:.w w] 的属性。

[method:Quaternion identity]()

设置该四元数为 identity 四元数，即表示“不旋转”的四元数。

[method:Quaternion invert]()

翻转该四元数 —— 计算 [page:.conjugate conjugate] 。假定该四元数具有单位长度。

[method:Float length]()

计算四元数的 [link:https://en.wikipedia.org/wiki/Euclidean_distance Euclidean length] （欧几里得长度，直线长度），视为一个四维向量。

[method:Float lengthSq]()

计算四元数 [link:https://en.wikipedia.org/wiki/Euclidean_distance Euclidean length] （欧几里得长度，直线长度）的平方，视为一个四维向量。如果要比较两个四元数的长度，这可能会十分有用，因为这比 [page:.length length]() 的效率稍高一些。

[method:Quaternion normalize]()

[link:https://en.wikipedia.org/wiki/Normalized_vector Normalizes]（归一化）四元数 —— 即计算与该四元数具有相同旋转、但长度为*1*的四元数。

[method:Quaternion multiply]( [param:Quaternion q] )

将该四元数与[page:Quaternion q]相乘。

[method:Quaternion multiplyQuaternions]( [param:Quaternion a], [param:Quaternion b] )

将该四元数设为 [page:Quaternion a] x [page:Quaternion b] 。
改编自 [link:http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/code/index.htm here] 所概述的方法。

[method:Quaternion premultiply]( [param:Quaternion q] )

Pre-multiplies this quaternion by [page:Quaternion q].

[method:Quaternion rotateTowards]( [param:Quaternion q], [param:Float step] )

[page:Quaternion q] - The target quaternion.
[page:Float step] - The angular step in radians.

Rotates this quaternion by a given angular step to the defined quaternion *q*. The method ensures that the final quaternion will not overshoot *q*.

[method:Quaternion slerp]( [param:Quaternion qb], [param:Float t] )

[page:Quaternion qb] - The other quaternion rotation
[page:Float t] - interpolation factor in the closed interval [0, 1].

Handles the spherical linear interpolation between quaternions. [page:Float t] represents the amount of rotation between this quaternion (where [page:Float t] is 0) and [page:Quaternion qb] (where [page:Float t] is 1). This quaternion is set to the result. Also see the static version of the *slerp* below. // rotate a mesh towards a target quaternion mesh.quaternion.slerp( endQuaternion, 0.01 );

[method:this slerpQuaternions]( [param:Quaternion qa], [param:Quaternion qb], [param:Float t] )

Performs a spherical linear interpolation between the given quaternions and stores the result in this quaternion.

[method:Quaternion set]( [param:Float x], [param:Float y], [param:Float z], [param:Float w] )

设置该四元数的 [page:.x x]、[page:.y y]、[page:.z z]和[page:.w w]属性。

[method:Quaternion setFromAxisAngle]( [param:Vector3 axis], [param:Float angle] )

从由 [page:Vector3 axis]（轴）和 [page:Float angle]（角度）所给定的旋转来设置该四元数。
改编自 [link:http://www.euclideanspace.com/maths/geometry/rotations/conversions/angleToQuaternion/index.htm here] 所述的方法。
假定*Axis*已被归一化，*angle*以弧度来表示。

[method:Quaternion setFromEuler]( [param:Euler euler] )

从由 [page:Euler] 角所给定的旋转来设置该四元数。

[method:Quaternion setFromRotationMatrix]( [param:Matrix4 m] )

从[page:Matrix4 m]的旋转分量中来设置该四元数。
改编自 [link:http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm here] 所概述的方法。

[method:Quaternion setFromUnitVectors]( [param:Vector3 vFrom], [param:Vector3 vTo] )

Sets this quaternion to the rotation required to rotate direction vector [page:Vector3 vFrom] to direction vector [page:Vector3 vTo].
Adapted from the method [link:http://lolengine.net/blog/2013/09/18/beautiful-maths-quaternion-from-vectors here].
[page:Vector3 vFrom] and [page:Vector3 vTo] are assumed to be normalized.

[method:Array toArray]( [param:Array array], [param:Integer offset] )

[page:Array array] - （可选）存储该四元数的数组。若未指定该参数，则将创建一个新数组。
[page:Integer offset] - （可选）若指定了该值，结果将会被拷贝到该 [page:Array]。

在形如[x, y, z, w]的数组中，返回四元数中的数字元素。

[method:this fromBufferAttribute]( [param:BufferAttribute attribute], [param:Integer index] )

[page:BufferAttribute attribute] - 源 attribute。
[page:Integer index] - attribute 中的索引。

从 [page:BufferAttribute attribute] 中设置该四元数的[page:.x x]、 [page:.y y]、 [page:.z z]、 [page:.w w]属性。

静态方法

[method:null slerpFlat]( [param:Array dst], [param:Integer dstOffset], [param:Array src0], [param:Integer srcOffset0], [param:Array src1], [param:Integer srcOffset1], [param:Float t] )

[page:Array dst] - The output array.
[page:Integer dstOffset] - An offset into the output array.
[page:Array src0] - The source array of the starting quaternion.
[page:Integer srcOffset0] - An offset into the array *src0*.
[page:Array src1] - The source array of the target quatnerion.
[page:Integer srcOffset1] - An offset into the array *src1*.
[page:Float t] - Normalized interpolation factor (between 0 and 1).

Like the static *slerp* method above, but operates directly on flat arrays of numbers.

源码

[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]