Quaternion API

3D rotation maths as an API: convert freely between quaternions, Euler angles, axis-angle and rotation matrices, compose rotations, rotate vectors, and interpolate. The convert endpoint takes any one representation — a quaternion {w,x,y,z}, Euler angles (roll, pitch, yaw), an axis and angle, or a 3×3 matrix — and returns all four forms at once, normalized. The multiply endpoint composes two quaternions (the Hamilton product) so you can chain rotations. The rotate endpoint applies a quaternion to a 3D vector. The slerp endpoint does spherical linear interpolation between two orientations along the shortest path — the standard way to animate smooth rotations. Euler angles use the aerospace Z-Y-X (yaw-pitch-roll) intrinsic convention in degrees; quaternions follow the Hamilton convention with order w,x,y,z; matrices are row-major right-handed. Everything is computed locally and deterministically, so it is instant and private. Ideal for game and graphics engines, robotics and drones, IMU and sensor fusion, aerospace and flight dynamics, VR/AR, and 3D content tooling. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 5 endpoints. This is 3D rotation maths; for 2D geometry use a geometry API and for plain angle-unit conversion use an angle API.