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Character Assembly with SurfaceContinuityManager+
By Jeremy Birn

This tutorial will show you how to extend the Zipping process described in the previous tutorial to the task of attaching legs to an animal's body. Once the body is properly assembled, SurfaceContinuityManager+ will be able to hold all of the surfaces together seamlessly during animation and rendering. To begin the tutorial, load the scene scm-tutlegs. (This comes in a zip file from the SCM Tutorials page.)

At the starting point, the body and the leg are two separate objects with gaps between them. Their edges do not face each other, so they cannot be zipped together as the grids were in the previous tutorial. SurfaceContinuityManager+ will only be able to hold them together if they have rows of points already aligned in matching positions, a situation that does not exist yet.

While this may seem counter-intuitive, the first step towards unifying these surfaces with the Surface Continuity Manager is to start by further dividing them. The leg will need to be cut into 4 slices, and the body will need to be cut into 8 rectangular surfaces, in order to expose compatible edges that can be zipped together.

NOTE: If Zip Surfaces fails to work as shown, it is because the two surfaces were not properly matched in steps 6 and 7. Use Info > Selection to verify that they truly have the same number of points running along their shared edge, instead of just counting the points by sight. Sometimes cutting NURBS surfaces produces situations where two rows of points can overlap near an edge, effectively hiding a row of points from you.

NOTE: After you have completed this step, your results should match the models in the hierarchy named "Zipped."

This process of attaching legs to a body has introduced a basic technique of seamless stitching, which is extensible to many other modeling tasks. No matter what the shape of the surfaces, similar patterns can be assembled again and again, so that the steps followed in this tutorial would be applicable to many other modeling situations.

The Pattern

Viewed as flat surfaces, the basic pattern that was followed for attaching a leg could be seen as follows:

The center four surfaces of this pattern were the four quarters of a leg in this tutorial. This is a useful pattern that recurs many times in NURBANA models. The next tutorial uses the same basic pattern to insert an eye into the surface of a head.

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This tutorial copyright © 1999 by Jeremy Birn.
Please do not duplicate any part fo this tutorial without written permission.