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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, they just bend 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 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
    Commented Jul 27, 2016 at 10:14
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    $\begingroup$ See blender.stackexchange.com/questions/56713/… for the best possible answer. $\endgroup$ Commented Jul 27, 2016 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. $\endgroup$ Commented Jul 27, 2016 at 11:29
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    $\begingroup$ 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
    Commented Jul 27, 2016 at 12:28

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I make quite extensive use of Bezier Curve objects in Blender, I use them a lot more than I actually use mesh objects.

I work mainly in architecture mostly doing archviz, decoration and interior design projects. This is not a popular nor a 'standard' modeling technique, and I am well aware how exotic it is, even in similar business areas.

Curve objects in Blender suffer from severe limitations when compared to meshes, like limited availability of modifiers, poor texture mapping capabilities, can't be unwrapped, can't have particles or participate in Boolean Operations, and can't be rigged or easily animated with armatures like meshes do.

Although Geometry Nodes alleviated most of these, their very limitations are also their biggest strength, and when taken advantage of provide particular constraints that make them well suited for these use cases.

Bezier Curves

By being inherently bidimensional, bezier curve objects (in 2D Mode) automatically guarantee a flat 2D surface, avoiding dealing with accidental non planar surfaces unintentional caused by negligent geometry snapping, which is a frequent occurrence in real world situations.

Because they you don't have to work with faces directly, you don't have to worry much about topology nor maintaining a good edge flows like you would with mesh objects. This alone lifts a huge burden and frees you from worrying about mico-managing geometry.

Hard-edge modelling is easier, mixed straight and curved shapes live happily together, automatically handled by the bezier handle types and curve fill engine as well; so you also avoid having to worry about adding support edge loops or unwanted smoothing in straight areas.

Since curves have a builtin quality setting for curved segments smoothness you don't have to use Subdiv Modifiers which are often a source of concern for topology, while maintaining quality settings non destructive.

Because the fill engine also handles automatically inner curves and recursive shapes inside shapes it easily creates holes and islands inside outlines, avoiding extensive use of Booleans, which are slow, error prone and a frequent source of frustration.

The builtin beveling, offsetting and extrusion features allow for a non destructive workflow, which you can easily go back to and change parametrically without having to redo manually.

Bevel objects also allow defining extrusion shapes along complex paths, common in metal work, frames and railings frequently found in architecture, and often provided in CAD format by manufacturers.

In building and construction area, Bezier curve objects end up being very versatile in designing:

  1. Building walls, which can conveniently be defined as an extrusion of an architectural plan outline, that is often already provided by the client, guaranteeing planar closed shapes with dimension accuracy.
  2. Facades, curtain walls, and elevations can also be easily defined from client provided elevation drawings, since again they are often mainly bi-dimensional extrusion structures with holes and island that are well defined from a 2D closed curve with holes for windows, doors, openings and stonework around them.
  3. Pavement finishes or floor areas (like an room with a certain type of wood, carpet or ceramic tile finish) which are defined by a closed boundaries combining complex shapes with mixed curved and straight geometries.
  4. Concrete slabs, or extensive ceilings areas with arbitrarily shaped openings for lighting and holes for installed equipment, are also easy to define because you don't have to worry about topology, manually deal with gaps, fill holes nor use booleans.
  5. Railings, metal work, extrusion profiles and frames along complex paths are easily handled by the builtin Bevel objects.
  6. A lot of other real world objects made from sheet materials (like table tops, wood board, wood furniture benefit from the same advantages like easy extrusion, tessellation and bevelling.

Other than that, they are also very useful as complement for 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 you never deal with faces directly, the emphasis on precision, trimming, Boolean operations and CSC (Constructive Solid Geometry).

Looking at Blender alone it's hard to imagine using them as an actual full featured 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. have actually usable and full featured NURBS modelling tools, capable of very accurate surface definition, surface trimming, Boolean operations, etc.

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

Paths

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 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
    Commented Jul 27, 2016 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. $\endgroup$ Commented Jul 27, 2016 at 13:04
  • $\begingroup$ Aren't bezier curves and nurbs curves mathematically the same thing? $\endgroup$
    – June Wang
    Commented May 19, 2020 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". $\endgroup$ Commented May 19, 2020 at 19:07
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Think of Bezier curves like nurbs, but on steroids. But as we all know, steroids can get you into trouble!!! There's a great film on youtube (link below) that shows that they're actually kinda like the same thing as N curves.

You know that first, 4 point N curve you get when you first create it? Well, just think of B curves like a whole series of those, joined together. Once you start to see these "troughs" in your B curves, it makes it much easier to manipulate them how you want!

https://www.youtube.com/watch?v=Qu-QK3uoMdY

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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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