New Rhino / Cinema 4D Import / Export Plugin announced

 From:  Michael Gibson
3642.3 In reply to 3642.1 
Hi Nigel, yeah it sounds like it won't work with 3DM files from MoI because it does not actually process the NURBS data in the 3DM file, it only grabs render mesh data attached to the NURBS models.

When MoI writes a 3DM file, it only writes NURBS data to the file, and does not store display/render mesh data in there as well.

That's because saving display meshes produces a lot of bloating in file size, often times in Rhino 3DM files the display meshes can increase the file size by many times with render mesh data actually taking up the majority of the increased file size.

Rhino basically has to store the render mesh data because its mesher is very slow to calculate the mesh data. So in order to avoid waiting for a long time for meshes to be generated to make an initial shaded display it stores the display meshes in the file.

MoI solves that problem by just having a very fast mechanism for generating display meshes, so it can do it dynamically when the file is loaded rather that bloating up the file.

Having a fast display mesher also solves other problems as well, because whenever you change a model it has to be re-meshed in order to be displayed. That's why it can be painful to work with Rhino in a shaded display mode, where you'll end up seeing the "calculating meshes" message a lot.

You also can't get the same mesh quality from Rhino display meshes either - the display meshes are limited in several aspects as compared to the meshes you get in OBJ format. For example a Rhino display mesh does not have n-gons in it, and also it cannot have welded points where 2 polygons share the same point but have different uvs or normals.

So because of these limitations, it would not be a good solution for MoI to store render mesh data in 3DM files, you would end up getting a lower quality mesh result than what you can get currently by exporting from MoI in OBJ format.

- Michael