Stitching a NURBS character
Leg to Body

After attaching the arm, you'd think that attaching the leg would be a cinch, and it is, if you know what you're doing. The process I'll describe is the way that's worked best for me in the past. Feel free to modify it if it doesn't suit your exact needs.
In Figure 1, you see my scene. Again, I'll work with the super Hero from my 3D Stills Gallery. As you can see, the body and leg are both fully formed, leaving out the entire pelvis/groin area. Also, to simplify things, the openings at the bottom of the body and top of the leg are flat across, not at any sort of irregular angles or whatnot. This isn't necessarily required, but it does kind of make the process a bit easier and quicker.Figure 1
First you want to check # of spans, surface direction, and seams. In Figure 2, you'll see that the seam of the leg is running down the inner thigh. In order to move your seam, there's a couple ways to do it, depending on the program you're using. If you're in the newly released Maya 4.0 (lucky! :), simply select the isoparm that you want to make your seam and go to Edit NURBS > Move Seam. In Maya 3.0, however, you'll have to select the isoparm you wish to make your seam and detach the surface at that point (Edit Surfaces > Detach Surface).Figure 2
In Figure 3, you see the wireframe of the torso mesh. If you look closely, you notice that the U direction is running UP the body and the V direction is running around. You want the leg to do the same. If it is not, use the Reverse Surface Direction options (Edit NURBS > Reverse surface Direction > Options) to make it match.Figure 3
Next you want the spans to match. In my case, I need the V direction to match each other. Use the Rebuild Surface Options (Figure 4, Edit NURBS > Rebuild Surface > Options) with 0 to #Spans, U OR V check (depending on your situation), and CVs UNCHECKED. Now, use the slider for the direction you need and rebuild either surface to correspond with the other. In my case, I rebuild the leg to be 17 spans in the V direction to match the torso. (The reason I need so many is because the torso model is highly detailed with realistic, although exagerrated, musculature. :)Figure 4
Now for the Fillet. Like in the arm attachment, I like to use the Fillet Blend Tool (Edit NURBS > Surface Fillet > Fillet Blend Tool) For it to work, you select one isoparm, press ENTER, select the other, and press ENTER again. The fillet, should form between them. However, watch out for what happens in Figure 5. Obviously, that's WAAAY too many spans! If this happens, undo (Z) the action and select the 2 isoparms in the reverse order. As you can see in Figure 6, this works fine. Again, this only works correctly, if both surfaces have the same number of spans in the correct surface direction. Figure 5Figure 6
With the surface's History still in place, you can now model this portion into the pelvis area without worrying about the seams coming undone. Using this method does have a couple of drawbacks, however. As you can see in Figure 7, you'll always have a hole in the groin of the shape, so if you want a view of this area for... uh... whatever reason, then another method might be better for you. But...Figure 7 seen in Figure 8, this is a workable method of attaching the leg to the torso of a NURBS character.Figure 8
I hope this tutorial has helped you! Any errors, suggesions, comments are welcome. Pleae contact me!

Michael McKinley