Nurbs Nerds

[Owen]

Having spent far too much time with Nurbs in the last three weeks - I've had enough..

There must be some way to automate the control of these unruly buggers!?

I understand that Friendship have developed a tight grip with the loss of certain design freedoms, but what of a fairing algorithm that jiggles all the CP about whilst maintaining surface shape, with an end result of a fairer surface..

Don't tell me all these supercomputers are good for nothing in the world of hull design!?!?

[Gilbert]

What software are you using?

[nero]

Surf the TouchCad website. One of the best things about TC is that the handles of the control curves are directly on the lines.

Getting a fair surface can be easy. First up use as few control points as possible. Use the scale tool or command as much as possible. Then there is always changing the amount of control points comand. This last one interpolates the curve with the number of points you enter.

Also look at the jaggies. As you look along a line along, the stair steps will tell you the direction of the curve.

There are some expensive meshing programs in the FEA and CFD areas that will smooth out a mesh. But to reach that level of a design, one would already have a design smooth enough to be built.

[yipster]

"Don't tell me all these supercomputers are good for nothing in the world of hull design!?!?"
check out the programs in the software section and you may want to have a look at T splines

[Tim B]

By Nero: There are some expensive meshing programs in the FEA and CFD areas that will smooth out a mesh. But to reach that level of a design, one would already have a design smooth enough to be built.

Nero - can I point out that a grid generator is not a tool for smoothing or repairing gemoetry? It's a tool to create a mesh that matches the geometry.

I'm sure I've said it before on this forum. Good Geometry, Good Mesh, Good Result.

That goes for all geometry of course, just because you can't build to 1/1000 of a millimeter, doesn't mean that your CAD drawing should be any less accurate. If you start with clean, accurate geometry you will ALWAYS end up with a better result/build (or whatever).

NURBS is actually quite an easy system to use, once you get into it. For anyone wanting to understand it fully I strongly suggest that you sit and write some code to draw a NURBS Curve (or surface). Once you've done that you'll find yourself creating clean geometry almost by default!!

Cheers all,

Tim B.

[nero]

Okay Tim B. You are correct.

But, from the hours of reading (with no personal worthwhile experience in the FEA side) , many of the meshing programs talk about repairing and smoothing the mesh. Much of this has to do with joints between surfaces that do not touch or share points. But some of them can bring the joint between two surfaces fair. Some of them will add a fillet and build it into the mesh.

Regards,