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I know that Beziers, Nurbs curves and Paths have different controls:

  • Bezier handles have control over tangents, and the curve always touches the control point
  • Nurbs curves don't touch the control points, the curve just bends towards them. The curve doesn't reach the first or last control points, but ends around the second/second-last point.
  • Paths are the same as Nurbs curves, except the curve continues to reach the first and last control points.

But what are the practical differences between them? What can a each of them be used for that the others can't, or what about each of them makes them easier to use for certain tasks?

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    $\begingroup$ that can help ? blender.org/manual/modeling/curves/… $\endgroup$ – lemon Jul 27 '16 at 10:14
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    $\begingroup$ See blender.stackexchange.com/questions/56713/… for the best possible answer. $\endgroup$ – metaphor_set Jul 27 '16 at 10:15
  • $\begingroup$ It would be much better to ask just about their differences, and let the practical applications to the user. Because it is dependent on the thing you want to do. For different situations different curve types fit the most and to name all the situations is much harder than to name just the curves differences and let the user to understand them, let him think with own head and apply the knowledge to specific practical tasks. $\endgroup$ – Jaroslav Jerryno Novotny Jul 27 '16 at 11:29
  • $\begingroup$ Knowing the differences is easy. Knowing what difference those differences make is a matter of experience and trial+error. I was hoping someone could summarize some of the common applications of each curve type in an answer, explaining why it was best for that case. $\endgroup$ – Greg Zaal Jul 27 '16 at 12:28
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I must say that I make extensive use of Bezier Curve objects in Blender, I use them a lot more than I use actual mesh objects actually.

I work mainly in architecture though, so I mostly make archviz and interior decoration projects. I know this is not a popular nor a 'standard' use of Blender, and I am perfectly aware that most people's workflow is far different from mine, even in similar business areas, in fact I don't think I've ever seen any anyone else use a similar technique.

That being said I find that bezier curve objects are very useful mainly for extrusion based shapes which are common in this business.

Bezier Curves

In building and construction area, Bezier curve objects are versatile for building walls, which can conveniently be defined as an extrusion of an architectural plan outline that is often provided by the client.

Facades and elevations can also be easily defined with a bezier curve from client provided elevation drawings since again they are mainly bi-dimensional extrusion structures that are well defined from a 2D closed curve with extrusion, along with windows, doors and stonework around them.

Floor areas (like an area with a certain type of finish), concrete slabs, and arbitrarily shaped areas with mixed curve and straight shapes, and extensive ceilings with wholes for lighting equipment, are also easy to define using bezier curves, mainly because you don't have to worry about maintaining good topology to close all gaps and fill the ends. They are inherently flat by nature with a simple extrusion that can be defined procedurally (no destructive modelling), and you don't have to manually deal with topology because they are procedurally filled and automatically tessellated.

A lot of other real world flat objects (like table tops, wood board based shapes, flat sheets) benefit from the same advantages like easy extrusion, tessellation and beveling.

Bezier curves can also be useful for other more three-dimensional objects with tube like extrusion geometries like pipes, wires, railings and other tube based shapes.

Other than that, they are also very useful as complement for more illustration based graphical design type of work, like Logo design and symbol creation, or 2D type of motion graphics often used in TV, video and animation work.

NURBS

NURBS surfaces on the other hand are more suited for smooth almost organic-like shapes used in vehicle design like cars, boats, airplanes, or more aerodynamic industrial design objects.

They differ from subdivision surface because of the emphasis on precision, trimming, and Boolean operations.

Looking at Blender alone it's hard to imagine using them as an actual full features modelling tool, since Blender's NURBS tools are admittedly a stub, with very limited features and lacking tools.

They are there more as a remnant of the past than as an actual production ready tool. Other dedicated software like Rhino, MoI, Katia, etc. has a lot more usable and versatile NURBS modelling tools, capable of very accurate surface definition, surface trimming, Boolean operations, etc.

They are very suited for actual technical drawing extraction, since correct and exact elevations, plans and sections can be extracted from a NURBS or Solid based 3D model.

Paths

I don't frequently use them myself, but from what I gather they are mostly used for animations purposes, mainly to define animation paths objects must follow, sort like a railway. They are probably mathematically more accurately and precisely defined, yielding smoother animations and avoiding jitters and sudden movements while animating.

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  • $\begingroup$ Nice examples with the beziers, never thought of using them like that. About nurbs, I was referring to the nurbs curve objects, not the nurbs surfaces. $\endgroup$ – Greg Zaal Jul 27 '16 at 12:47
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    $\begingroup$ Ah yes, I don't think I've ever used a 2D NURBS curve as alternative to bezier. My guess is they are better at defining organic shapes, as opposed to mixed or straight-segments curves with beziers. Also depends on the desired actual shape of the curve, as you mentioned with bezier you define pass-through points, and with NURBS you refine tangents. $\endgroup$ – Duarte Farrajota Ramos Jul 27 '16 at 13:04
  • $\begingroup$ Aren't bezier curves and nurbs curves mathematically the same thing? $\endgroup$ – June Wang May 19 at 15:15
  • $\begingroup$ Not sure about the internal workings, but I've heard paths are more accurate. In practice the way you control them is also different, one passes through points, the other is "fit through". $\endgroup$ – Duarte Farrajota Ramos May 19 at 19:07
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You guys are so wonderfully technical. LOL. For me, the practical difference between the two types of curves in my artwork is that the N-curve lets me put the vertices of the curve exactly where I want them. The B-curve is for me madly confusing making those curves end up in the right place. It may seem tedious but I will almost bet that I can beat anyone time wise creating a complex of curves using the N-curve, extrude, click (rinse and repeat)like a little race car running around the contours of my design.

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