This shows you the differences between two versions of the page.
rhino:meshtonurb [2015/09/14] |
rhino:meshtonurb [2020/08/14] (current) |
||
---|---|---|---|
Line 1: | Line 1: | ||
+ | ====== The MeshToNurb Command ====== | ||
+ | > **Summary: | ||
+ | |||
+ | =====MeshToNurb: | ||
+ | | ||
+ | To fully understand what this operation does, familiarize yourself with some of the basics of 3D constructive geometry as well as characteristics of both mesh and NURBS objects. | ||
+ | |||
+ | =====Meshes vs. NURBS===== | ||
+ | To understand what **MeshToNurb** does, one must also understand the fundamental differences between a //Mesh// model and a //NURBS// surface model. | ||
+ | |||
+ | A mesh represents 3D surfaces as a series of discreet facets, much as pixels represent an image with a series of colored points. | ||
+ | |||
+ | NURBS surfaces are mathematical representations of curves and surfaces. | ||
+ | |||
+ | It is important to note here that NURBS can be easily converted to Meshes at any time, in the same way that you can easily take a digital image of a person’s face with a camera. | ||
+ | |||
+ | |||
+ | ===Mesh terminology used in this article=== | ||
+ | To repeat, meshes are faceted representations of 2D and 3D surfaces. | ||
+ | |||
+ | **Important note: | ||
+ | |||
+ | ===NURBS terminology used in this article=== | ||
+ | There is a huge amount of information available on NURBS. It is a very complex subject and will not be discussed in detail in this article. NURBS are curves based on mathematics. | ||
+ | |||
+ | =====OK, so much for all the technogeekspeak...===== | ||
+ | The **MeshToNurb** command - **//what does it do, really?//** | ||
+ | |||
+ | ===What it doesn’t do:=== | ||
+ | As stated above, MeshToNurb does not automatically " | ||
+ | |||
+ | ===What it does:=== | ||
+ | MeshToNurb will convert a (faceted) mesh structure to a (faceted) NURBS structure. | ||
+ | |||
+ | ===How it is done:=== | ||
+ | **Mesh Quads** are converted to 4-sided untrimmed degree1 NURBS surfaces. | ||
+ | |||
+ | **Mesh Triangles.** Triangles are by definition planar. | ||
+ | |||
+ | Based on the above, the resulting polysurface from MeshToNurb will have **// | ||
+ | |||
+ | **Important note:** MeshToNurb will not subdivide the quad areas into triangles to create planar surfaces. | ||
+ | |||
+ | =====Things to watch for:===== | ||
+ | |||
+ | ===Memory use and file size=== | ||
+ | |||
+ | Mesh objects can contain from a few to hundreds to thousands to millions of polygons. | ||
+ | |||
+ | ===Downstream operations=== | ||
+ | |||
+ | If you now have a NURBS object produced by MeshToNurb composed of many thousands of tiny NURBS surfaces (just like the mesh was) what can you do with it? Not much – most normal operations will probably fail... | ||
+ | |||
+ | ===Geometric considerations=== | ||
+ | An understanding of the type of geometry produced is essential. | ||
+ | |||
+ | =====With all its limitations… what is this command useful for then?===== | ||
+ | |||
+ | ===Converting low poly mesh models=== | ||
+ | |||
+ | MeshToNurb is useful for converting low-polygon count meshes that are mostly planar into NURBS surfaces for further work in Rhino. | ||
+ | |||
+ | ===Unrolling objects=== | ||
+ | Since you cannot currently unroll mesh objects, you can use MeshToNurb and then unroll the resulting polysurface. | ||
+ | |||
+ | ===Exporting to programs which do not support meshes=== | ||
+ | Again, beware of file sizes, but occasionally this can get you out of a jam, although you will still have a faceted model. | ||
+ | |||
+ | //WIP msh 13.04.2011// | ||