More concepting: mesh and nurbs

This topic is reaching a fever pitch, I’m just fanning the flames. The wall that has existed between mesh modelers and NURBS modelers is eroding quickly. If you’re not too clear on what all this is, here is a brief primer.

Mesh is a term that denotes the data created by systems like 3D Studio Max and Maya. Autodesk owns both of these products. Mesh modeling is used for game character development, and also movie animation. A model is defined by a set of points in 3D space, and then shaded by connecting all of the points into triangles, and smoothing between the triangles. Animation is created by defining how sets of points react to the motion of a stick skeleton. Mesh can be used for product development, but mainly for visualization. Because the mesh data so closely resembles STL data (stl is a form of mesh), meshes also work well for rapid prototyping, except that mesh modelers typically don’t have a way to hollow out the material on the inside, and so rapid prototypes directly from mesh can be expensive because they use too much material. In general, mesh models are not thought to be accurate enough for manufacturing, because you start with the inherent limitation of the faceted/tessellated face of the model.

NURBS is a more mathematically accurate way of representing general curved surfaces. If the mesh is a series of small, flat triangles defined by point position, NURBS is usually made of larger rectangular patches of curves defined mathematically. NURBS is far more accurate than mesh, but because of all of the calculations needed to create that accuracy, it tends to be slower than working with mesh, and is less easy to change.

To over simplify the issue, use silly stereotypes and risk offending everyone:

Mesh = kid with tattoos, a knit wool cap and dreadlocks on a skateboard (games and animation)

NURBS = married guy with a tie and pocket protector at a desk in a cubicle (CAD)

Not surprisingly, these two worlds have found it difficult to communicate. It is easy to save out a NURBS model as an STL, but it is far less easy to create NURBS data from a mesh model. In fact, people usually just remodel the mesh in a NURBS package, although there are more NURBS tools for working with mesh data than ever. SolidWorks a year or two ago came out with ScanTo3D, which is a rather unfortunate name because it appears to limit it to scanned data (point cloud data also resembles mesh data), but can work just as well with meshes. Another product is Geomagic Raindrop has existed for a long time and is the industry standard for this type of work. Another new offering is RapidWorks. More on that later.

What I really wanted to talk about here was the interview at Novedge of the Autodesk media & entertainment marketing guy. The worlds of the punk-ass-kids and sedate desk jockeys are going to collide. He talks about using mesh modeling in product concepting, and visualizing the mesh data in Inventor (NURBS modeler). In an earlier post I talked about integrating Alias (high end NURBS) with Inventor (low end NURBS), which would appear to be directed at manufacturing product design. The integration of 3DSmax or Maya with Inventor seems to be aimed at concept modeling, or “digital prototyping” as Autodesk so originally calls it.\n\nSo am I jumping ship to Autodesk products to animate game characters? Well, it would beat working for a living, but I don’t think I’m ready for that yet. It would be fun to play around with in all of my spare time. No, I’m just looking down the road to see what if anything this is going to mean for new capabilities in SolidWorks. Much of the focus of late in SolidWorks has been directed somewhere other than the core mechanical design. I think SolidWorks is trying to shift its weight and become more of a competitor for Autodesk rather than simply for AutoCAD. (WAG warning!! [wild ass guess])

Speaking of WAG warnings, Josh Mings, another SW blogger, comes to what seem to me to be bizzare conclusions about the matter, but maybe someone else can read it and explain to me the connection between Alias and web based PLM. The leap of logic I don’t get is where he doubts that “Dessault” (sic) views the integration of Alias with Inventor (mechanical product design software) as any sort of competition, but if they do, they should respond with web browser based CAD and portable viewing devices to make paper obsolete. Whatever. I think they do see it as competition, at least the SolidWorks side of Dassault, and that they will respond by offering a product or combination of products to compete.

Renewed interest in Cosmic Blobs Pro (mesh modeler) also fuels speculation that something is brewing in this direction. CB Model Pro is at least as old as August 06, probably older. The original Cosmic Blobs is 3-4 years old, and is sold in retail big box stores, I understand.

Combine all of this mesh modeling hysteria with the laser scanning hysteria, and we have a real reason to bring mesh and NURBS closer together. In an upcoming post, I’m going to be talking about techniques to convert from mesh/point cloud data to NURBS either manually or automatically using ScanTo3D and RapidWorks. This is becoming a more important task in today’s digitally connected design and modeling world. More tools of the trade.