# 5 sided hole

When faced with a challenge like this (and these are challenging!) the first thing to figure out is the optimal patch layout - everything will flow from that. In order to find the basic patch layout, I first simplify everything to the greatest extent possible - you first have to figure out how to model the general shape, and then tailor and tweak to make any specific shape. So, in this case, I’ve greatly simplified the input curves. It should also be noted - every single one of these curves is highly suspect from a surface modeling standpoint. They’re pretty garbage-ey, to be blunt - there’s a strong whiff of AutoCAD spline tools all over them. You’re never going to make a quality model by directly using them as input. Anyway, I rebuilt all of them to degree 5 single span or less, and started playing around. The real breakthrough for me came when I made a blend between the main neck loft, and a guide surface I’d created at the outside corner:

This blend is curvature to the neck loft, tangent to the guide surface:

I created a trim curve along the blend surface, by pulling a blend and then rebuilding single span.

I then made this surface using Surface from Edge Curves:

From there, it’s a matter of sculpting and matching your surface to get to your desired tangency on all surfaces. For me, since this is a woodworking piece that will get extensively hand finished, it’s hard to see any reason to go below 0.1 degree, and that’s probably overkill as it is. I’m working on an entire video called Zen and the Art of the Trimmed Edge, but if you pull the surfacing apart you’ll notice that the trimmed edge is not single span, it’s 2. In short, what I’ve found is that for best results when matching to a trimmed edge, I’ll up the degree to 5, then I’ll insert a span from 1 to 2, and then after that if I need I’ll keep adding degrees. Surfaces over degree 5 that are single span suffer from some issues when matching to trimmed edges, but inserting a knot/span into them using the natural option will keep the MatchSrf math “stable” much more often. So you’ll see the trimmed edge ends up at 7-2. This trimmed edge is fairly complex - it’s relatively long and doing quite a bit of “work” so the point count will need to be a bit high. That being said, I think this is a case where a trimmed edge is superior to an untrimmed solution.

This is only a patch layout study, but to me this feels like the best/most viable way forward proposed thus far. Alternately - doing these in subd is quite a joy! I did a whole bunch of necks and heels for Santa Cruz Guitar back in the day using T-Splines. For things that have that hand carved feel, often you can capture the feel and shape better with subd, so it’s a route I’d encourage you to test out.

-Sky

3 Likes