This page shows the step by step process for creating a complex human face from digitized data. This tutorial uses NURBS curves and surfaces that will have isoparms that align.
People would create a model like this for several reasons. Models that are built this way will bind inside of Maya and Alias with clusters that will not tear surfaces at the seams. This also enables rapid and accurate conversion to polygons. Polygonal models can be painted in Amazon Paint and Flesh, and exported into systems there NURBS surfaces cannot be used.
The process shown here was used to create the head models shown below.
|Head Final Shaded||Head Final Wire Frame|
Terms used in this page:
Isoparm: The lines within and surrounding a surface when a surface is constructed from curves. The number an placement of these lines correlate with the number and placement of the edit points on the curves that create the surfaces.
Parameterization: A surface has an inherent range of values along each side. These values are also related to the number of isoparms, and thus, the number of edit points in the curves that created the surface.
These values are measured in values of "U" and "V". In the case of a single span skin surface (using the same curves on each side to construct the surface), the "U" values correspond to the number of edit points on the curves on each side. The "V" value would be "1" by default.
These values relate also to the number of "spans". By selecting the single span skin surface, and reading the information window sats on the selected surface, you can see that the "spans" relate to the way the surface was constructed.
When you begin to attach, detach, insert, and rebuild surfaces, you
begin to make changes to the number of spans in the surface , and thus,
the parameterization .