Creating a New Network

One of the main features of PACE is that it is very quick and easy to create a patch arrangement. It is thus possible and also desirable to experiment with various patch configurations. It is wise to start by loading into PACE the main construction curves; FOS, FOB, stem profile, stern profile, transom, stem tangent curve, sections

PACE allows patches to be created from either boundary information or boundary and data describing the interior of the patch. The data describing the patch is derived from any part of a curve that cross the boundaries of the patch and lie within its interior. Even though ultimately we may wish to incorporate data from all of the curves into the definition of the patches. Initially, it may be better to rely just on boundary information to create the patches. The reason for this is that it is quicker to create patches that do not use data, so it is faster to get an initial patch configuration. Further, if these non-data patches, that use only boundaries, give reasonable results, it is more likely that when we come to using data, the final result will be acceptable. If data is to be used it is advisable to choose a patch size of ten or twelve. The patch size is the number of control vertices (polygon points) along the edge of a patch (see General Page).

Figure 3:140. Basic boundary curve set

Figure 3:141. Basic curve set and surface

It is worth noting that flat patches are not restricted to be bounded by three or four edges as are curved patches. This has an important effect on possible patch configurations. It means that it is possible to stop a curve such as a waterline on the edge of a flat patch, such as the FOS, without having to carry it all the way through the length of the vessel. If the patch boundaries imply a curved patch with more than four sides, then this patch cannot be created or displayed. Additional curves must be added to the network of patch boundaries to overcome this problem. Further, if the boundaries of a patch imply that it is flat, then no attempt is made to alter the tangency at its boundaries, as this would then make the patch non-planar.

Figure 3:142. Surface after addition of extra curves