squat: simple quaternion library

A simple quaternion library for JavaScript.

API documentation

squat's API assumes quaternions are represented as an array of four numbers. Given such an array q, a quaternion is:

q[0] + q[1]*i + q[2]*j + q[3]*k

Functions that return a quaternion typically have an optional argument, at the end of the argument list, which serves as an "out" parameter. If the caller passes an object (like an Array, or a Float64Array) via this argument, the function will set the '0', '1', '2', and '3' properties on the object with the computed quaternion's component values. This can be used to recycle space in a preallocated chunk of memory in an array buffer and avoid allocating space for return values.

squat.add(q1, q2, [out])

Adds two quaternions.

squat.mul(q1, q2, [out])

Multiplies two quaternions.

Note: quaternion multiplication is noncommutative.

squat.scale(q, x, [out])

Scales the quaternion q by the scalar value x, multiplying each component by the scalar.

squat.conjugate(q, [out])

Computes the conjugate of a quaternion.

squat.inverse(q, [out])

Computes the inverse, or reciprocal, of a quaternion.

squat.length(q)

Computes the length of a quaternion. Also known as the "norm".

squat.normalized(q, [out])

Normalizes a quaternion so its length is equal to 1. The result of normalizing a zero quaternion is undefined.

squat.real(q)

Provides the real part of a quaternion, as a number.

squat.vect(q)

Provides the vector part of a quaternion, as a three-element array.

squat.zero([out])

Provides an empty quaternion, with all components set to zero.

squat.from_axis_angle(axis, angle, [out])

Constructs a rotation quaternion, given an axis and angle. The axis should be an array or array-like object holding three numbers. The angle is in radians.

squat.angle(q)

Extracts the angle part, in radians, from a rotation quaternion.

squat.axis(q)

Extracts the axis part, as an array of three numbers, from a rotation quaternion.

License

This library is released under an MIT license.