Fiber optic shape sensing uses embedded sensors to measure the full 3D shape of a flexible surgical device along its entire length in real time. By sensing the device itself from the inside, it provides continuous awareness of how the device bends, twists, and turns as it moves. Optical fiber shape sensing is a form of distributed sensing that uses scattered signals from a multi-core fiber to determine curvature and twist rate to produce the shape of a given structure. In this work, we propose a novel, computationally efficient method for determining the 3D tip position of a bent. S.