Euler spiral

An Euler spiral, also known as a "spiral of constant curvature" or "clothoid," is a curve in which the curvature changes linearly with the arc length. This means that the radius of curvature of the spiral increases (or decreases) smoothly as you move along the curve. The curvature is a measure of how sharply a curve bends, and in an Euler spiral, the curvature increases from zero at the start of the spiral to a constant value at the end.