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There are many different types of modeling technologies available to the 3D artist today. There are six common types of model data that can be used to generate a 3D model on a computer, and each of these offer distinct advantages and disadvantages to the 3D artist, regardless of their chosen discipline. This short series of articles will examine each of these types individually. You can find the previous article on NURBs here, and Polygons here,   Subdivision Surfaces

Catmull-Clark subdivision of a cube, showing progressive smoothing of the surface. Image credit Wikipedia.

Catmull-Clark subdivision of a cube, showing progressive smoothing of the surface. Image credit Wikipedia.

Subdivision surfaces are a relative newcomer to home 3D applications, but are now supported by virtually every 3D modeling and animation package. In many ways, they are the most popular method of displaying curved surfaces in 3D space, due to their ease of use, wide implementation, and good surface qualities. They work by iteratively adding detail to an object to create predictable smoothed surfaces from basic geometry.

A subdivision surface showing the rougher polygonal control cage in green. Image credit: Author.

A subdivision surface showing the rougher polygonal control cage in green. Image credit: Author.

Subdivision surfaces use an easy to edit polygon control cage, and a workflow similar to polygon modeling; individual faces and vertices are selected and moved to adjust the form of an object. Additional detail and creasing is performed by adding edge loops to a model, and models are built via a series of tools, such as extrusions, bevels, etc. Subdivision surfaces are also easy to texture; just like polygons, they can be easily unwrapped for additional texture detail.

One of the weaknesses, or at least considerations, to be factored in when using subdivision surfaces, is something called polyflow. Subdivision surfaces smooth most predictably when interpolating quad-based models; triangles and n-gons (polygons with n number of sides) can cause a model to smooth in strange and unexpected ways. Thus models should be planned at least a little beforehand, with proper poly flow so as to minimize spiral loops, triangles, and ngons – though sometimes they may prove unavoidable. Above is an excellent video of various considerations when working with subdivision surfaces. For even more resources, you can look here on Polycount’s wiki.

Artist’s website Subdivision surfaces are excellent for smooth objects, or creating organic curves. They can be used for machinery, but the process is a bit more involved than a NURBs or polygon object; extra loops and edge weights have to be added to crease corners, and edge fillets are much less controllable than a NURB object. However, for ease of use in building complicated organic/smoothed forms efficiently, subdivision surfaces are at the top of the list. subdivlogos Try programs like BlenderMayamodoCinema4DLightwaveWings3D, or Silo3D to give Subdivision surfaces a shot. Any polygonal geometry built in other software can be brought into these packages and turned into a subdivision surface, however remember to keep your model mostly as quads. Below is a video of subdivision modeling using the free software Blender.

Pros:

  • Excellent at curved, smooth surfaces
  • Theoretically “infinitely smooth” surfaces allow for extremely high resolution meshes
  • Easy to edit using techniques similar to polygon workflows
  • Fast to render

Cons:

  • Less control than a NURBs surface
  • Has difficulty with irregular, non quad-based polygons
  • Hard surfaces could prove more challenging than other workflows
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