Vice President of Autodesk Labs, Brian Mathews, points out that DWF supports NURB surfaces, which are a much more compact way of defining a curved surface instead of tessellation and a much more accurate way as well. NURBS, short for non-uniform, rational B-splines, is a mathematical model commonly used in computer graphics for generating and representing curves and surfaces. NURBS provide a mathematically exact representation of freeform surfaces like those used for car bodies and ship hulls that can be exactly reproduced whenever technically needed. When a surface is stored in a DWF file as a NURB (equation) instead of geometry (polygons), the Autodesk DWF Viewer or Autodesk Design Review can tessellate the geometry at load time to any level of precision, since a NURB is a perfect mathematical definition.
We have all heard the old adage that prescribes a reliable way to settle a controversy: "If it walks like a duck and quacks like a duck, it's a duck."
The links to these DWF files are for a tessellated duck and a NURBS duck. (Yes we know the geometry has a missing path, but this is just a test file meant to show the difference in file sizes when using a NURBS definition versus a tessellated definition.) Shoot, even Dick Chaney can see that the NURBS duck is smoother in appearance and is one tenth the size.
Unfortunately none of our design applications (nor DWF Writer for 3D) publish NURB surfaces to DWF, but our DWF Toolkit, DWF Viewer, and Autodesk Design Review fully support it. We expect future versions of Autodesk publishing applications to make use of NURBS in DWF. On the other hand, C++ developers using the DWF Toolkit can take advantage of NURBS today. The ability to represent complex geometry exactly, instead of pre-scaled to one specific page size, is another way DWF goes beyond the paper.
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