algorithmic modeling for Rhino
Here is a script to calculate exact geodesic distance from points on mesh. It is a transcription of "Fast Exact and Approximate Geodesics on Meshes" from "http://research.microsoft.com/en-us/um/people/hoppe/geodesics.pdf" link. It could be used with one or more points. Many points could be used as an approximation of a curve.
The script need a mesh (without too many points) and some source points (at least one).
It outputs distances on each Vertex of the mesh, Isolines are calculated using Millepede plugin. As the script is not optimized it could lead to long calculations (~ 1 min with the example provided).