Wings 3D/User Manual/The Nature of Subdivision Modeling/Subdivision and Such

Subdivision and Such
Wings 3d is a polygon modeler that incorporates subdivision as one of its core functions. Wings and other modeling packages that subdivide polygonal meshes are often referred to as "subdivision modelers". Wings is also often called a "box modeler" since most models start out as a cube primitive.

Types of Subdivision
There are fundamentally three types of subdivision surface styles available for polygon modelers:

  Facet Simply subdivides (tessellates) the model without doing any smoothing.   Smooth ''Does the subdivision and smooths the model by displacing the resulting vertices. This makes it look much more organic, which is why subdivision modeling has become so popular for organic modeling.''   Metaform Metaform shows the smoothed model with the un-smoothed cage floating about it.  



To Smooth Or Not To Smooth
One of the mistakes new modelers often make is subdividing their models too soon, and/or too often. When modelers smooth too soon and don't get the organic form they were hoping for they then often resort to smoothing again, to make it look well... smoother. Some people will smooth a model three or four times to try and get it to look right. This is almost always a mistake. It creates very bloated models, meaning a high in polygon count, which devour lots of memory needlessly. If you take the time to hand craft in details, then one smooth is likely to give you the results you want, the model will be much more efficient, and it will most likely look better too.

Hard Edge Modeling: Keeping Edges Crisp
Often a model will lose desired edges and creases when it is smoothed. Fortunately there are several methods to keep sharp details even on a smoothed model.

There are three basic ways to ensure that an edge will stay sharp. You can use Bevel on corners to add a slight chamfer which will help preserve the detail, or you can add control edges on either side of edges you wish to remain defined.

Sometimes these are called mechanical bevels and they offer the most control over how a model appears after smoothing. You can also select the necessary edges and set them to Hard. Be sure the model export format and the rendering engine you intend to use support hard edges, or you may not get the results you expect. The added geometry of Bevels or Control Edges on the other hand will always do the trick.

Another reason to use Bevel instead of hard edges is that they help show off detail. It seems that sharp edges don't show specularity well, making details hard to see.

By giving man made objects softer edges via Bevel, it increases their specularity, thereby drawing out the detail that would otherwise be lost. Some online model stores will not even accept models for sale that do not use beveled edges to maintain detail, so avoid hard edges if you can.

And as with smoothing, some people tend to Bevel too soon in the modeling process. It should be one of the last things you do, unless you are using it to create new base geometry. The reason is that it overcomplicates your model, forcing you to manipulate many more elements than you otherwise would have had to deal with had you not beveled too soon.