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Based on the definition of smooth nodes vs smart nodes, there should be :)

Have you tried the Affinity Designer Help? If you open the Help file, and search for the term smart node, the first topic shown (About Lines and Shapes) will describe the difference between the two node types.


-- Walt

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See: the node tool and edit vector curves and shapes.

Also: About lines, curves and shapes

The type of node controls the connected segments. There are three basic types of node:

  • Sharp (A)—causes an abrupt change in direction between segments, creating a point.
  • Bézier (smooth) (B)—creates a continuous curve between segments.
  • Smart (C)—creates a continuous curve but uses a line of best fit.

☛ Affinity Designer 1.7.0 ◆ Affinity Photo 1.7.0 ◆ OSX El Capitan

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Actually I think Chris has a very good question.  Let's ask the question slightly different then, what is the meaning of "uses a line of best fit"?

 

I find I never use the Smart because I see so little difference between these two.  And the explanation of "uses a line of best fit" does little to make me decide to use the Smart.  I have tried each in various situations over the years and see very little difference between the smooth and smart.  At least nothing that would make me say "Ah the smart is the way to go."

5a5cb17dd15fe_ScreenShot2018-01-15at6_53_30AM.jpg.fb5a7bfbeef01451d8b159b49a92f156.jpg

Laying the smooth upon the smart...

5a5cb237779e6_ScreenShot2018-01-15at6_58_45AM.jpg.59ed0b44486d614ab028ee639a34b984.jpg

Why is one of best fit versus the other of poorer fit?

 

I'd really like to know why people pick the smart over the smooth or the other way around.


iMac (27-inch, Late 2009) with macOS Sierra

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Can't tell, they look pretty much similar without that much of a difference at all. But maybe there are other drawing usages where differences are then more obvious.


☛ Affinity Designer 1.7.0 ◆ Affinity Photo 1.7.0 ◆ OSX El Capitan

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Well if anyone can come up with an example Chris and I would sure like to see them.  We appreciate any input that can clarify what the best fit really means or does that is advantageous to the user.


iMac (27-inch, Late 2009) with macOS Sierra

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The difference between Smoth and Smart node you see, if you change the node position or your handle between two nodes of the given type - smart node changes the following segment.

"Best fit" means, that the neighboring segment tries to keep on to the one that has just been changed.

In Gear maker image try change the midpoint node position.


Affinity Photo 1.7.0.367, Affinity Designer 1.7.0.367, Affinity Publisher Beta. Affinity Store.
Windows 10 Pro, Version 1903, Build 18362.145.
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9 minutes ago, Gear maker said:

Well if anyone can come up with an example Chris and I would sure like to see them.  We appreciate any input that can clarify what the best fit really means or does that is advantageous to the user.

There is probably a formal mathematical definition somewhere, but I think "line of best fit" in effect refers to the collection of line segments that create the least area between them & all other possible line segments connecting the same set of points, excluding any segments that would cause abrupt changes in direction.

 

So for example, in the diagram below the five black dots represent the points (nodes) to be connected with line (curve) segments. The red line represents one of the infinitely many curves that could connect those points & the blue line represents the curve with the least area between it & any of the other possible ones, thus making it the "line of best fit."

5a5cbd5ae905d_bestfit.png.7e3399c3e262ed435aa2aa99826b7371.png

best fit curve.afdesign 


Affinity Photo 1.7.1 & Affinity Designer 1.7.1; macOS High Sierra 10.13.6 iMac (27-inch, Late 2012); 2.9GHz i5 CPU; NVIDIA GeForce GTX 660M; 8GB RAM
Affinity Photo 1.7.0.135 & Affinity Designer 1.7.0.9 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iOS 12.3.1

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Psenda, thank you for the reply. 

 

Okay after some playing I see what you are saying.  Let me paraphrase it so others get two explanations. 

 

Smart: With the nodes being smart, if one is moved then the smart node(s) on ether side of the moved node automatically adjust their handles to help smooth out the curve.

 

Smooth: With smooth nodes the handles on the node(s) on either side do not get moved when the node is moved.  Possibly causing some odd shaped curves.

 

One oddity I did notice is that if the segment between 2 smart nodes is nudged/moved, both smart nodes are converted into smooth nodes automatically.  Likewise if a node is added between 2 smart nodes, all three are automatically converted to smooth nodes.  Also when a handle is moved that smart node is automatically converted to be a smooth node.  Reconverting them back to smart nodes can cause a pretty good jump in the segments. 

 

Another oddity, if the shape is not closed and the handle of a node that is the second node in from either end is moved, then the handle on the end (smart) node will adjust itself to smooth the curve.  But the handle on any non end (smart) nodes will not be moved.

 

R C-R, maybe I'm not understanding what you are saying, but with the smart nodes the segments are sometimes shortened and sometimes lengthened to try to keep the curve as smoothly flowing as possible when responding to a node being moved.

 

Wow, there's a lot involved with smart vs smooth nodes.

 

Mike


iMac (27-inch, Late 2009) with macOS Sierra

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1 hour ago, Gear maker said:

R C-R, maybe I'm not understanding what you are saying, but with the smart nodes the segments are sometimes shortened and sometimes lengthened to try to keep the curve as smoothly flowing as possible when responding to a node being moved.

I know my explanation was not all that clear to begin with, but it isn't about the length of the curve per se but about minimizing the area 'under the curve' relative to all other possible curves through the same set of nodes. That probably is not any clearer but imagine filling in the areas between the blue curve & the red one, or between any two curves that pass through the same 5 nodes. The 'best fit' curve is the one with the least total filled in area. For the kind of Bezier curves Affinity uses, that will (I think) always be the one like the blue one that consists completely of 'smart' nodes.


Affinity Photo 1.7.1 & Affinity Designer 1.7.1; macOS High Sierra 10.13.6 iMac (27-inch, Late 2012); 2.9GHz i5 CPU; NVIDIA GeForce GTX 660M; 8GB RAM
Affinity Photo 1.7.0.135 & Affinity Designer 1.7.0.9 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iOS 12.3.1

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12 minutes ago, R C-R said:

The 'best fit' curve is the one with the least total filled in area

That's a straight line :-)

Why in Smart mode does the neighboring segment change, when I change the position of the adjacent node? "Best fit" is "best fit", and should remain unchanged.

In my view, they try to keep the smoothness of the curve as smooth as possible.


Affinity Photo 1.7.0.367, Affinity Designer 1.7.0.367, Affinity Publisher Beta. Affinity Store.
Windows 10 Pro, Version 1903, Build 18362.145.
Latitude E5570, i5-6440HQ 2.60 GHz, 8 GB, Intel HD Graphics 530, 1920 x 1080.

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36 minutes ago, Pšenda said:

That's a straight line :-)

Or the shortest connection between two points. ;)


☛ Affinity Designer 1.7.0 ◆ Affinity Photo 1.7.0 ◆ OSX El Capitan

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1 hour ago, Pšenda said:
1 hour ago, R C-R said:

The 'best fit' curve is the one with the least total filled in area

That's a straight line :-)

But it is not one that is free of abrupt changes in the direction of the curve, except in the trivial case of a path for which all its data points are in a single straight line. As I alluded to (none too clearly, I admit) in my earlier post, mathematically derived 'best fit' curves used in statistical analysis usually are designed to exclude any segments that would cause abrupt changes in the curve's direction. They may in fact not even go through every data point, so the analogy with these kinds of curves & those normally used in AD & other general purpose vector apps is not perfect.

 

Still, I think this is what the "continuous curve but uses a line of best fit" refers to in the help topic.


Affinity Photo 1.7.1 & Affinity Designer 1.7.1; macOS High Sierra 10.13.6 iMac (27-inch, Late 2012); 2.9GHz i5 CPU; NVIDIA GeForce GTX 660M; 8GB RAM
Affinity Photo 1.7.0.135 & Affinity Designer 1.7.0.9 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iOS 12.3.1

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