a migraine

definitely…meshes are also typically larger in file size/system overhead

but isn't the difference between mesh/surface similar to raster/vector??

A mesh is triangulated polygons approximating the geometry (the more dense the triangles, the closer to the actual geometry), whereas a "surface" is the actual mathematical expression of the geometry (NURBS and the like) and what you're seeing in the viewport is a translation of that expression (which is why the shaded bits don't always line up perfectly with the isoparms) for reference but any work done on the object is done on the actual expression, under the hood so-to-speak.

Rendering engines (and some other analysis-type tools) need meshes in order to work (the plugins for Rhino translate the surface into a mesh at rendertime); if for example you have the render mesh settings low--the rendered image will most likely be faceted instead of smooth (even though the surface you're working on in Rhino is perfectly smooth)

Ooooo..thanks!

so why would anyone want to use meshes versus surfaces?

there are no true meshes in rhino. it is essentially a simulated surface i.e. if you explode it, it becomes a series of surfaces.

meshes are in the category of 'solid modeling' which is a far different approach than nurbs modeling. solid modeling is the 'play-dough' approach where nurbs you start with curves. this is not very evident in rhino however, and meshes are more cumbersome than it is worth compared to other softwares like maya or microstation. load the UDT tools in rhino to find out why you would use meshes.

the mesh is more dense depending on the detail you need , always under a surface exists a mesh, just how tessellated it is is based on the settings need.

sometimes the last step when all edits are done, a final mesh would be the last step to export for other uses and programs.

ahh....makes sense.

thank you dot and antisthenes!

any one tell me exact diff between mesh and surface.