Hi Klingbeil,
> i'm trying to do this
> http://moi3d.com/forum/index.php?webtag=MOI&msg=817.4
> with a hex instead of a square
NURBS surfaces are fundamentally quad-like in structure. Whenever you have a surface that looks like it has more than 4 edges on it, those are actually trim curves cutting away some base quad-like surface.
It's not quite the same as a polygon quad because the "NURBS quad" is like a sheet of rubber and can be all bendy and have a lot of points in it instead of just 4 corner points, but every underlying surface is made up of a row and column quad-like grid of control points.
You can have edges of the surface squished together into a point, that's how for example spheres are made - those are quad-like surfaces that have their top and bottom edges all compressed down to a pole point.
To get something like that link but with a hex shape would involve making a similar kind of "pole" point as a sphere, with the pole at the center of the hex. You can use Rail revolve to make a shape like that, draw a line from the center of the hex to one edge, then select the line as the profile, run rail revolve, pick the quad as the path, and give a revolve axis vertical to the hex plane, and that should build a revolved hex surface with a squished together edge at its center. It will actually be split up into 6 different surfaces since there is a creased boundary around the outside and surfaces are split into multiple pieces at any sharp edges like that. Also you'll need to turn off the "Cap ends" option in Rail revolve so that it doesn't put a second plane surface joined on to it - it thinks there is a planar opening at the bottom since all the open edges are on the same plane.
I've attached a hex created in this manner - if you turn on control points for it you'll see that it actually has points at all juncture points instead of being trimmed.
You can build a repeated structure out of this tile and join them together and still get control points to turn on (until you do some boolean or trim or something that introduces trim edges instead of natural surface edges), but these are actually little separate triangle facet pieces and won't be a single big smooth surface when you distort their points unlike that example in that link.
- Michael |
