Is there a command to remove unneeded Isocurves from a nurbs surface


#1

When using the Mesh from polysurface command, Isocurves in a surface can cause this command to add more polygons than you may want. especially if you want to have a very low polygon count and have adjusted the detailed settings acordingly.

I am meshing some simple shapes made from sweeps.
The rail is a square with only knots in corners.

Here is an example or one side of the square sweep.


Is there a command to just remove isocurves from inside a surface such as this?

Here is the mesh of the above, with the minimum edge length set bigger than the length of the edge of the square


And here is a mesh of a surface using the same settings but I just made a surface from the planar surface from curve command of the same square.

I know there are workarounds Like Silhouetting the object, andthen with a relatively simpel object I can then just build the mesh manually.

Thanks


(Chris Kuether ) #2

Try ‘removeknot’


(John Brain) #3

Well - You can rebuild or fit the surface - depending on the surface itself you should get various results.


#4

Note on the terminology, “isocurves” are just curves drawn on a surface to indicate the shape, they’re not actually part of the definition of the surface–though the number of them Rhino draws is indicative of the number of knots in it(unless there are zero so it draws one along the middle.) Yeah it’s subtle.

It’s not actually the number of knots in the surface that affect the meshing as in your example, it’s whether or not the edges of surfaces are TRIMMED, trimmed edges are always meshed with triangulated edges, and PlanarSrf makes a planar surface by trimming off a larger surface with the input.


#5

That does not hold true on this simple example Jim.


#6

Yeah in that particular case it identifies the input a square and makes it an untimmed plane. In every other case though, it doesn’t.

In your original example, I believe you made some sort of a solid from a sweep, so it has JOINED edges, which are also triangulated since “joining” is actually sort of a “trimming” operation, the joined edge curves are added to the surfaces, and if you explode the object those edges remain until they are untrimmed.