Questions tagged [nurbs]

Non-uniform rational basis spline (NURBS) is a mathematical model commonly used in computer graphics for generating and representing curves and surfaces which offers great flexibility and precision for handling both analytic and freeform shapes.

Non-Uniform Rational B-Spline (NURBS) is a mathematical model commonly used in computer graphics and computer aided design for representing curves and surfaces which offers great flexibility and precision for handling both analytic and freeform shapes.

NURBS allow representation of geometrical shapes in a compact form. They can be efficiently handled by the computer programs and yet allow for easy human interaction. NURBS surfaces are functions of two parameters mapping to a surface in three-dimensional space. The shape of the surface is determined by control points.

NURBS are commonly used in computer-aided design (CAD), manufacturing (CAM), and engineering (CAE) and are part of numerous industry wide used standards, such as IGES, STEP, ACIS, and PHIGS. NURBS tools are also found in various 3D modeling and animation software packages, such as form•Z, Blender,3ds Max, Maya, Rhino3D, Cinema 4D, Cobalt, Shark FX, and Solid Modeling Solutions. Other than this there are specialized NURBS modeling software packages such as Autodesk Alias Surface, solidThinking and ICEM Surf.

125 questions
9
votes
2 answers

OpenGL NURBS surface

I'm learning OpenGL and I want to get a surface with a slight hump in the middle. I'm currently using this code and im not sure how to adjust the ctrl points to make it the way i want. Its currently like and i would like to have it like this: im…
Knitex
  • 225
  • 1
  • 6
  • 11
7
votes
1 answer

GLU NURBS rendered wrongly

EDIT: This is a library bug. I reported it to the HOpenGL mail list. I use 9-point rectangular method to represent a circle/ellipse as a NURBS. The points are p1, p2, ..., p9, p9 = p1. They lay as shown: y2 | p2 p3 p4 y1 | p1 p5 y0 | p8 p7…
modular
  • 1,099
  • 9
  • 22
5
votes
1 answer

Find the center of Curvature of a point on 3D b-spline using nurbs / geomdl in python

Once again I am in over my head so please bear with me. I have a B-spline (imported from Solidworks) that I can analyze with geomdl in python. From geomdl I can extract the first and second derivatives as well as the tangent, normal, and binormal…
Burtski
  • 451
  • 5
  • 19
5
votes
2 answers

Meaning of knots when drawing a NURBS curve?

I'm using gluNurbsCurve to draw some curves with some control points. I've got the basic setup as described in the red book working correctly and I'm trying to expand on it. This sample looks like this: float knots[8] = {0,0,0,0,1,1,1,1}; float…
shoosh
  • 76,898
  • 55
  • 205
  • 325
4
votes
1 answer

Implement closed B-Spline interpolation of datapoints

I have a set of 3D points which I am trying to interpolate using a pth-degree B-Spline. I have implemented the algorithm described here https://pages.mtu.edu/~shene/COURSES/cs3621/NOTES/INT-APP/CURVE-INT-global.html so that the curve passes through…
4
votes
2 answers

How to draw NURBs with OpenGL ES

In OpenGL NURBs can be drawn using evaluators. But it seems evaluators were removed from OpenGL ES spec to make it light weight. In that case, how can one draw NURBs using OpenGL ES API?
Jayesh
  • 51,787
  • 22
  • 76
  • 99
4
votes
1 answer

Compute a point on a spline surface

I am working on a control algorithm to be run on an embedded system. My programming language is C and the system will be pretty tightly constrained in terms of memory and processing power. I have a few (in the order of about 10) reference points in…
calamity
  • 41
  • 3
4
votes
1 answer

Slicing a NURBS surface

I have a NURBS surface which has 4 curved edges. (I have the 4 bezier points for the curves) I'd like to slice the NURBS surface with a slicing-plane thats on-axis (not as advanced as 3DSMAX!), and calculate a curve where the slicing-plane and NURBS…
Robin Rodricks
  • 110,798
  • 141
  • 398
  • 607
4
votes
1 answer

Understanding of NurbsSurface

I want to create a NurbsSurface in OpenGL. I use a grid of control points size of 40x48. Besides I create indices in order to determine the order of vertices. In this way I created my surface of triangles. Just to avoid misunderstandings. I have…
TimDor
  • 49
  • 1
  • 8
4
votes
2 answers

NURBS on DirectX 11?

Can you render NURBS on the GPU with DirectX 11? I've been reading up on current trends to rendering surfaces like these, but I don't see anything on NURBS. I found some related references, but nothing solid... like "Approximating Catmull-Clark…
davidotcom
  • 51
  • 4
4
votes
1 answer

How to create a cubic bezier curve when given N points in 3D?

So I need to find out where the control points would be for a cubic bezier curve when only knowing points on the curve, the points can lie in 3D. It would be ideal if I could do this for any number of points on the curve. Most of what I have found…
Saebin
  • 404
  • 6
  • 14
4
votes
1 answer

How to know a specific value position using a Nurbs with OpenGL?

I am using OpenGL to create a nurbs surface (gluNurbSurface(...)) and I would like to know how reach the normal value to the control points(black dot) to the surface market as a red dot. With this information I will be able to calculate the distance…
Ivan
  • 119
  • 1
  • 8
3
votes
1 answer

Exporting BSpline/NURBS control polygon and Knot vectors from Blender

Given a Blender file with one BSpline/NURBS surface (for example, Add -> Surface -> NURBS Sphere), I'm interested in exporting its control polygon (the 3D points which define it) and its Knot vector. The exact format is less important, as long as…
user1071136
  • 15,636
  • 4
  • 42
  • 61
3
votes
3 answers

NURBS Library supporting trivariate NURBS

Does anyone know a free (as in free beer) C, C++ or even FORTRAN library that supports operations not only NURBS curves and surfaces but also Volumes (i.e. trivariate NURBS)? I know about open nurbs, but as far as I know it does not support NURBS…
Matthias
  • 506
  • 5
  • 16
3
votes
1 answer

NURBS surface to watertight stl

I've been making a parametric design using NURBS implementation geomdl in python. the problem is that it is hollow and cannot be processed with cgal or 3dprinted. I am looking for a way to make it watertight by closing the top and the bottom. I…
TrieHard
  • 41
  • 2
1
2 3
8 9