## Glossary

gimbal lock

When applying 3 or more successive rotations about axes that are orthogonal to each other, gimbal lock occurs when a degree of rotational freedom is lost due to two or more axes that cause the same effective rotation.

orthonormal

A transform has the property of being orthonormal if the three basis axes are all orthogonal and the three axes are normal (have a length of 1).

quaternion

A four-dimensional vector that represents an orientation. The first three components of the quaternion, the X, Y and Z, are considered the vector part of the quaternion. The fourth component is the scalar part.

inverse matrix

The inverse matrix of the matrix M is the matrix N for which the following equation is true: MN = I, where I is the identity matrix. The inverse of M is usually denoted as M-1.

conjugate quaternion

Analogous to the inverse matrix. It is computed by negating the vector part of the quatenrion.

spherical linear interpolation, slerp

Interpolation between two unit vectors that is linear based on the angle between them, rather than the vectors themselves.