Cross sections representing rendered surface

Hi, apologies im new to rhino and modelling. I have a mesh that I have imported from a 3d scanner (STL file). I realise I cant easily manipulate this file in rhino so i am trying to create a new object using the mesh as a guide. I am creating lines and projecting them onto the mesh.
My question is that the projection appears to be shown projecting onto the mesh itself i.e. the series of flat surfaces. Is it possible to get the projection to project onto the rendered surface.
I realise this is a basic qn, so if there is topic that people can recommend I read up on to understand it more then let me know or if there is a particular tutorial that may help my understanding then that would be great.

I am not sure it is the most right and easy way to resurface a mesh, but me personally is using mesh just as a guide to construct curves. I am using interpolated curves with Vertex snap, that way they follow the mesh pretty closely. After sketching the rails and profiles I simply hide the mesh, and continue as usual.

Hi Drew - I think you are supposing that the ‘rendered’ surface is smooth and the mesh is faceted, correct? That is not the case- the rendering of the the mesh as smooth, if that is how you are seeing it, is done with trickery- it is not in fact smooth. Use the FlatShade command to see the shaded mesh without the visual smoothing applied. Note in RhinoSpeak, meshes and surfaces are completely different types of data. ‘Reverse engineering’ meshes to surfaces cleanly is one of the trickier tasks in surfacing. There is some info here:


Hi, thanks for your replies. I think I understand. It was the fact that the system can display a mesh as rendered that was confusing.
I assume it is because all the lines on my scanner mesh are straight whereas the lines on a rhino created surface can be actual curves. I just thought if it is powerful enough to effectively do what I am trying to do so it can render a mesh for me to look at, could that not be used. It seems there is a lot more to it than this that I don’t understand (or need to as a user) I will just accept that it can’t be done that way!
Most of my work with rhino will start with scan data captured from a David SLS scanner, but I do need to do lots of modifications to the models once I have the scanned shape in there and then get the items cnc machined, so lots to learn! Thanks for the help so far!

I have just read the link Pascal, thanks very much, great info.