This week, 2 different approaches to building a 3D model. I'm still trying to find a comfortable way to approach the modeling process and build something up quickly. For a subject I went back to my slug friend from a few weeks ago. At work we use 3DS Max for all of our modeling activities, so I've been making an effort to get used to the program. Both 3DS Max and Maya (and Blender for that matter) are general modeling programs and have basically the same kind of interface. Modeling is basically done by manipulating vertices, edges, and faces. It's a very "engineering" like approach, and although there are some tools to help you build things up quickly --- mirroring, soft selections, and stock primitives to work from --- in the end it comes down to moving points around little by little.
Here's my rough model of the slug in Max:
Another approach to modeling are 3D sculpture programs like Mudbox and ZBrush. In these programs you use 3d tools to sculpt and mold a model like clay. This has several advantages: you can sculpt something quickly, you can generate a lot of detail, and it feels much more "artistic". However the final models are much more complex (they have many more faces, which means longer render times), and you don't have as much control over the structure which can make the final model difficult to animate later on.
Here is the same character modeled in ZBrush:
It feels much easier to add the little details that give something character in ZBrush, but the resulting models are kind of messy. In practice I think often pros would make a basic rough model in Maya or 3DS Max and then import that into ZBrush or Mudbox for details.