VIDI's Presenter 3D has been an indispensable tool for teaching 3-D modeling and animation at our university. After trying to work within the limitations of other 3-D packages, we finally found the one software that would allow our students the creative freedom to model anything they could imagine. When we purchased a lab copy of Presenter 3D in 1991, we discovered the true heart of the program was its use of b-splines (Bezier). It has been a vital part of our animation program at James Madison University. With its multitude of features, it has helped our graduating students obtain jobs at the top animation and multimedia companies from New York to Los Angeles. With its continuing development of professional character animation tools, Presenter 3D will be instrumental in helping future JMU alumni secure the best positions in the industry.

Parametric Surfaces

The most sophisticated and useful modeling packages use parametric surfaces. These are freeform curved surfaces that can be manipulated by bending or straightening their splines. There are several different splines available in different modeling packages. The two most suitable ones, Bezier and NURBS are usually only found in higher end modeling software. Bezier splines alter the wire mesh model directly on its surface while NURBS influence the mesh with a control hull. Both Bezier and NURBS based modelers are the best ones for modeling characters and other organic forms. Beziers allow one to curve the spline by manipulating its direction line. NURBS use a set of control vertices (CVs) arranged in a geometry matrix called the surface's control hull. This hull acts as a kind of exoskeleton to the spline and controls the shape of its surface. Modelers that use NURBS are more sophisticated than ones that use Beziers because the resulting models have smoother surfaces. Since Beziers influence the shape of the model directly on its surface rather than through a hull, it is quite common to see creasing. The problem of creasing usually is not a concern until one has to create a more sophisticated model such as a face. My forthcoming book, 3-D Human Modeling and Animation will show how to get around this b-spline limitation.

Spline based modelers belong to a category named the bicubic patch. This describes a surface mesh that is flexible because its splines can be bent. A less flexible method uses bilinear patches. These can be manipulated at the vertex level, but the surfaces remain rigid and cannot be curved. The least useful modeling software uses primitive surfaces called polygons. The basic problem with polygons is that they are flat and it takes a great number of them placed side by side to form a curved surface. If one desires a more detailed model, then one has to use more polygons which will require a greater amount of computer memory. The most primitive polygonal modelers will not allow one to change the surface characteristic of the model except to enlarge or reduce the form's entire dimension. Presenter 3D's use of Bezier splines puts it in the category of the select few modelers useful for creating anything one can see or imagine.