Changing tangency conditions

The degree of smoothness across individual patch boundaries can be controlled using the tangency controls. These are displayed for all patches by selecting DISPLAY \ PATCH \ TANGENCY or . Each patch has 8 tangency controls - one along each side, and one on each corner (for 3-sided patches, there are no controls on the corners of the degenerate edge).

The tangency controls affect the behavior of lines of control points next to those running along the patch edges, as shown in Figure 3:109 below- these determine the tangency conditions along the boundaries. The transition between two patches can be made smoother by aligning these control points from both patches across the boundary, as shown in Figure 3:110.

Figure 3:109. The control points (highlighted) that determine the tangency conditions around the edge of the patch.

Figure 3:110. Aligning adjoining control net legs across a patch boundary improves the smoothness of the join between the patches.