Suppose that the surfaces K0 and Kr are the boundaries of two convex, complete, connectedC2 bodies in R3. Assume further that the (Euclidean) distance between any point x in Krand K0 is always r (r > 0). For x in Kr, let Pi(x) denote the nearest point to x in K0. Weshow that the projection Pi preserves geodesics in these surfaces if and only if both surfacesare concentric spheres or co-axial round cylinders. This is optimal in the sense that the mainstep to establish this result is false for C1;1 surfaces. Finally, we give a non-trivial example of a geodesic preserving projection of two C2 non-constant distance surfaces. The question whether for any C2 convex surface S0, there is a surface S whose projection to S0 preserves geodesics is open.
2020 Mathematics Subject Classification: 52A15, 53A05.