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1answer
33 views

drawing NURBS: knots, multiplicity, divide by zero?

I'm trying to grasp how NURBS curves work. I think I understand the principle, but I'm unsure about the formula. Here, I base myself on this course. From a DXF file, I got the following parameters: <...
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1answer
150 views

B spline curve generation in Python

I am using the de boors algorithm to generate B splines in python. However I am getting spikes in the final figure. I do not understand why this happens. I am posting my code here for reference <...
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0answers
40 views

B splines curve generation [duplicate]

I'm using the de boors's algorithm to generate b splines in matlab. I have managed to generate a curve based on the control points I have given. Unfortunately I have noticed spikes in the curve. I do ...
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1answer
92 views

How does the Lane resienfield algorithm work?

I understand de castlejeau's algorithm and I am familiar although not fully experienced with B-Splines. I am trying to understand the geometric interpretation of B-splines through the algorithm (just ...
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1answer
147 views

Normalize NURBS knot vector

I have NURBS surface data. I have a list of control points, knot vectors in U and V params and the degree. The U knot vector lies in range -3.14 to 3.14 and the knot V vector lies in range -100 to 100....
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1answer
283 views

How do CAD programs render non-polygonal 3D objects?

How CAD programs handle displaying B-Reps and NURBS/T-Splines in their viewports? Assuming viewport uses OpenGL API - are those programs transform every object into triangles and creating/deleting ...
6
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1answer
118 views

How to sample 3D points to visualize a B-spline surface?

Given that I have implemented a function called calc_bspline_surf() in C, and that function has the following declaration: ...
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0answers
45 views

Making surface with common parametrization from bunch of other surfaces

I have bunch of surfaces, like in these two images: Currently to make single surface with common parametrization I sample points uniformly from all source surfaces, and fit single NURBS surface from ...
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1answer
228 views

NURBS topology classification

In what sense is it true that a NURBS surface can only have the topology of a plane, cylinder or torus? For example I can do a NURBS sphere. Is the sphere homeomorphic to one of the above surfaces?
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1answer
410 views

NURBS knot multiplicity

In Splitting of NURBS curves there the answer relied on "maximum knot multiplicity". In order not to mix-up different topics I would like to kindly ask to answer it in another question: what is this "...
8
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1answer
680 views

Splitting of NURBS curves

Splitting Bezier curve into two parts at some parameter t is easy thanks to De Casteljau's algorithm. Is there a similar algorithm for NURBS curves? How to split a ...
6
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1answer
241 views

NURBS curve drawing

How to draw a NURBS curve? Compared with Bezier curve, I just evaluate the Bernstein polynomial, multiply it with control point positions and that's it. Looking at the "General form of a NURBS curve"...
5
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1answer
215 views

NURBS curve offset

One of the benefits of NURBS curve over, say Bezier curve, is the ability to create offset curves exactly. How to proceed with such computation? Do I just translate the control points?
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1answer
1k views

Non-uniform rational B-spline (NURBS) Basics

I'm trying to understand NURBS curves (surfaces later!) but I have some trouble understanding the very basics of its inner workings. Could someone please explain a few things to me? As I come from ...