I lofted two clean, closed, non-planar, star-shaped curves with matching control-point structures. I used Patch for the top and bottom surfaces and joined everything together. So far, so good—it is a valid closed polysurface.
However, when I look at the star in Top view using the Technical display mode to see the hidden edges at a glance—for example, to identify possible undercuts for CNC machining—I see some strange, irregular lines that are not visible in Shaded mode at all.
Some of these lines belong to the top surface and others to the bottom surface. I figured this out by exploding a copy of the polysurface and selecting the individual surfaces.
Does anyone know what is going on here? How can I get rid of this fuzz?
Thank you for taking the time to answer. I’m still a little confused, but I think I understand the issue better now.
I start with a very clean, closed, non-planar NURBS curve — from watching many of your tutorials I have learned how important clean, well structured curves are.
I use it for Patch, since that seems to be the easiest way to create a smooth surface from such a complicated boundary.
In my case, Patch produces a much more complicated trimmed boundary.
I think my actual mistake was creating the sidewalls from the original clean curves and then joining them to the Patch surfaces. Since the Patch edge is slightly different, they did not fit perfectly, and my AI-Grasshopper setup – I am rambling to the AI and it does things – used some hacky fixes to force them together.
What solved the problem was creating the sides from the actual Patch boundary, so everything matches exactly.
Thank you for all your tutorials — I’ve learned a lot from them!
when you built your surface using patch (which is fine) the edge curves end up being trimmed.
trimmed edge are always quite complex and as such you can use them, but ideally you should use simpler curves and surfaces that represent the intersection you want, (by overbuilding them) then trim them back. that way the transition surfaces between your primary surfaces are much lighter.
The idea is to simplify all the surfaces that make up your model, so that limits how much building you want to do from trim edges. To clarify, this is a goal, not a do or die rule. I use trim edges often if I have to get somewhere fast, but I also am very aware of the risks and consequences of that choice and have already decided how I’m going to handle them down stream before I do so.
Sky does an amazing job bringing this point home here in his primary surfacing video series, which I recommend to everyone and never miss a chance to share the links-
