flipangle

Flipangle is a term encountered in computer graphics and animation to describe the magnitude of a flip transformation applied to a model or sprite with respect to a chosen axis. It is commonly used to denote the orientation difference between two poses or views, such as switching a character from facing left to facing right. The precise meaning of flipangle varies by tool, but it is generally treated as an angle parameter that controls a flip or mirrored orientation.

In three dimensions, a flip can be implemented as a rotational or reflective operation. A pure reflection through a plane perpendicular to a unit vector n is described by the matrix F = I − 2 nn^T, which flips components across the plane but preserves distances. A rotation around axis n by angle θ is described by Rodrigues' formula. In many systems, the term flipangle refers to the angle used in such a rotation to achieve the flip, often constrained between 0 and 180 degrees.

Common applications include sprite flipping in 2D games, character rigging in 3D animation, and camera-orientation controls in interactive software. The concept helps separate pose logic from rendering, allowing efficient toggling between facing directions or mirroring experiences without duplicating geometry. Caution is needed because flips can alter handedness when reflections are used, whereas rotations preserve it.

See also: rotation, reflection, Euler angles, axis-angle, quaternion.