[Bf-funboard] Restrictions in the order of the NURBS Surface

[Siddharth Palaniappan]

Hi,

I wanted to add that I have noticed that the bezier surface is not being drawn correctly on the control grid. Rather I think it leaves the first row/column of the control grid. Can someone please check this? The bezier surface(NURBS with bezier knots) should be such that the surface should interpolate thru the end control points. That is the end knot vectors should have degree + 1 multiplicity of knots. Is there anyway , I can set the knot vectors for the surface myself? Is there a way I can set the knot vector via the Python Script?

Thank You,

Yours Sincerely,

Siddharth

----- Original Message ----
From: Siddharth Palaniappan <siddharth_univ at yahoo.com>
To: bf-funboard at projects.blender.org
Sent: Wednesday, December 27, 2006 7:47:07 PM
Subject: [Bf-funboard] Restrictions in the order of the NURBS Surface

Hi,

I'm kinda new to blender. I see that there is a restriction in the order of 6. I was wondering why this restriction has been placed. Also I find it wierd to work with bezier knot vector arrangement. For example, if i have 4 points along U and V(default arrangement) and try order = 4 along U and V with bezier knot arrangement. I get no patch. But If i reduce the order to 3 along U and V, i get a patch.(a quadratic patch) 

I tried increasing the vertices by extruding the edges along U and V and then used order 4 along U and V. After extruding, we have a 5*5 control net and I get a cubic patch. 

The point is , it seems that there has to be an extra set of points which are usless when i want a bezier patch. I was wondering if the term order is wrongly used for degree? After all in bezier
 curves/surfaces,  order = degree + 1.

I am currently trying to write an importer/exporter and i find it difficult , as certain patches are more than order 6. And also because of the bezier problem.

If these problems could be fixed, it would be great since Blender could be greatly be used in our university in research. I dont know if the things I mentioned above are bug/problems. If not, please explain them to me.

Thank you,

Yours Sincerely,

Siddharth



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