Modeling a NURBS head (General Concept Tutorial)
Figure 7-4 The first three curves against a template. The second and third ones begin to define the side of the nose and gradually turn away from the first one. Their farthest points from the first curve is at the back of the head.
Some software packages let you rebuild curves so that they have matching points. This means that you do not have to worry about drawing each curve with the same amount of points. Once you finish drawing all the curves, then simply select the rebuild curves option and select uniform for rebuild type. Be sure to specify approximately thirty points for the number of spans.
It is usually a good idea to loft the curves as you continue to draw or duplicate and move them (Figure 7-5).
Figure 7-5 Editing the curves on the partial loft against a templated three dimensional head.
This will give you a general idea of how it will turn out and hopefully avoid unpleasant surprises. If your software has a history option like MayaTM, SumatraTM, or RhinocerosTM you can move the second curve's points to deform the mesh surface until you are satisfied with the results. If you are using a three dimensional head to model from, try templating it and use the X-ray Shade Option for the lofted section. This will let you see the relationship of the loft to the template as you deform the original curve. Another useful tool in MayaTM is the Layer Editor. You can use it to keep the curves and the three dimensional head in separate layers which in turn can be hidden and/or templated. When you are finished refining the curves, you can delete the temporary lofted section, leaving only the splines.
Resume drawing/copying and moving points on the new duplicated curves. Around curves three and four, you will most likely have to shape the wings around the nostrils. Many 3-D artists consider this part to be one of the most difficult sections of the face. This is especially true when trying to form the hollow at the corner of the wings. Some artists prefer to model that section separately and then use a fillet blend to join it to the rest of the nose. If you prefer to keep the entire nose as a part of the overall mesh, then shape the hollow at the wings by keeping two of the adjoining curves close together at this point. Remember to loft parts of the curves and make corrections accordingly.
As you continue drawing/duplicating and moving curves check the spans in the U and V surface direction. The connecting spans can be seen after lofting sections. They should flow smoothly without any severe angles. You can usually spot areas that will cause you problems later on. These will be ones were the curves lack that gentle turn. Figure 7-6 illustrates the head when almost all the curves except the ones for the jaw have been drawn.
Figure 7-6 Edit the points so that the curves in both the U and V directions flow smoothly.
When you start to shape the curves of the cheeks, the number of points that you needed for facial detail start to accumulate in a smaller area. This often increases the likelihood that the surface becomes more bumpy. The side of the face leading to the under surface of the jaw can be one of the more difficult areas to form. This process of creating curves and correcting surfaces is one of the more tedious aspects of modeling a head. The extra time that you spend on this will save you a great amount of labor after the final loft. Figure 7-7 shows all the curves for half the head.
Figure 7-7 The finished half face. Note the directions of the U and Vcurves. The placement of points on each curve will determine the success of your connecting lines.
Once you finish making all the curves for half of the face, then loft the entire set. At this point, it would be a good idea to tweak the original curves with history on to smooth out any bumps on the mesh.
Duplicating and Mirroring the Curves
When you are satisfied with the curves and the placement of their points, then select all of them, except for the middle ones, and duplicate them. While the copied curves are still selected, mirror them so that they are located on the other side of the face (Figure 7-8). Starting with the top middle curve select each of them in a clockwise or counterclockwise direction. Loft all of these with the close option on.
Figure 7-8 Curves are duplicated and mirrored for the other half.