Jump to content

Bad NURBS, bad!!!


kiwi

Recommended Posts

Does anyone know wy a scrip building a nurb suface with "CreateNurbsSurface()" and "NurbsSetPt3D()" (on the right V and U order) give me a surface smaller than the same points building a 3D poly. A bit like if the surface was build by control instead of interpolation...

Is any other nurb function that will create the exact surface describe by my points?

Link to comment

quote:

Originally posted by kiwi:

Does anyone know why a scrip building a nurb suface with "CreateNurbsSurface()" and "NurbsSetPt3D()" (on the right V and U order) give me a surface smaller than the same points building a 3D poly. A bit like if the surface was build by control instead of interpolation...

Is any other nurb function that will create the exact surface describe by my points?

Link to comment

I listed something that might be comparable in this thread... http://techboard.nemetschek.net/ubb/ultimatebb.php?ubb=get_topic;f=21;t=000216

Andrew Bell provided me with an answer in the VS mailing list:

Nurbs have an additional set of parameters not shown in the OI palette:

the knot values. Explaining exactly how they work requires showing some

reasonably complex mathematical expressions, so I'll just tell you the

code you need:

NurbsSetKnot(h1, 0, 3, 0.5);

NurbsSetKnot(h1, 0, 4, 0.5);

###

I don't know if that gives any insights, but it tells me that these are complex beasts whose complexity is never fully visible. So when you're trying to replicate something, you're doing it without seeing all the information used by the nurbs.

Link to comment

Interesting! after u,v, index,weight and degres, we have knots... and this time I couldn't find any reference on the pdf's other than the short descriptions on the related functions, and the exemple about the "cos surface".

Since, I script each "u" curve and loof them: works not so bad, but don't give a great control over the shape. Will study this Knots: any idea where find more info about how they react to math and trigo?

Thanks,

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...