Created attachment 165861 [details] Fisheye Perspective Curves are segments of Perfect Circles Krita's Fisheye Assistant is using the wrong kind of curves. The Fisheye Assistant is currently using ellipses for its curves. However, a proper Fisheye Perspective can only be achieved by using segments of perfect circle. In fact, Krita's Curvlinear Perspective Rulers is doing this the correct way -- it makes sense too -- Fisheye perspective is just an application of Curvlinear Perspective. Although the effects of using ellipses and perfect circles might look similar, ellipses only works for projecting spherical objects on a flat screen -- for example, a photo of a globe. As such, it can only loosely mimic 1-point dead-center Fisheye Perspective. If we increase the center points for more complicated Fisheye Perspectives, this misuse of curves will prevent people to understand how things works, and things fall apart. A will attach a proper Fisheye Perspective guideline for reference.