To see how my smooth drawing is forced into aligned nodes, see https://youtu.be/bGruR4Ce3d0 for a ~30 second demonstration. You will see that the results are the same before and after turning off snapping. Smoothing on the pencil tool is down to its lowest setting- 1. I switch to the node tool after making the drawing. You can see how ridiculous is it.

The thing is, it's not just this tool. Some artwork made external has started to open up all square, basically ruining it. This is making Inkscape unusable.

OS: OSX El Capitan. 10.11.4
Inkscape version: 0.91
XQuartz 2.7.7

Things I have tried:
Reinstalling Inkscape.
Turning off snapping or turning down all snapping distance settings to the lowest setting.
Deleting the Preferences.xml file.

I hope that someone here has an idea about this- Inkscape has become ruined for me in its current state.

You could try these hints:

- Leave the Spiro mode: look at the top, where the tool bar for the pencil tool is. There are two modes, one spiro, one normal.
- Also make sure that the stroke you are applying does not have any dashes set and that its width is set to a reasonable value (Fill and stroke dialog - open via Object -> Fill and Stroke, third tab).

I'm not sure you deleted the correct preferences.xml file, that should have reset the spiro mode, at least...
Hope this helps!

And if these don't help - please tell us which download file from our website you used. Did you use any experimental builds or the official ones?

Thank you for the reply. I'm afraid that I was expecting a notification to appear if there was activity on this post, and I had not gotten one. I was seconds away from buying Illustrator when I decided to look one more time and confirm.

In regular mode (versus Spiro) the tool creates a very similar result. I notice that in my video, I only have the fill settings set, and I have changed it to stroke 1.2 pixels, no dashes. No difference.

I have to say now that this is not the only function affected by the problem. Opening external vector files, say, converting from AI, produces a very similar looking effect. The paths are very square on an image I know to look smooth, either from a PNG version also provided to me, or because I had opened the file in the past without this rigid or rectangular node corruption going on.

The file for installing is from
https://inkscape.org/en/download/mac-os/
and is specifically
Inkscape-0.91-1-x11-10.7-x86_64.dmg

I notice now that OS X El Capitan is 10.11, whereas the link above says the Inkscape version is for 10.7-10.10. Perhaps there is an issue with 10.11 compatibility? I don't remember exactly when I upgraded versus noticing problems with Inkscape.

The preferences.xml I deleted was in .config/inkscape/preferences.xml, which was rewritten when I started a new Inkscape session. I retained the previous file to perform a diff, and although there are some differences, the behavior did not change- hence this thread.

Thank you again for your suggestions (I have clicked the option below to notify me for a reply).

Can you upload a file that you created with this? (There isn't a bug report at https://bugs.launchpad.net/inkscape for this yet, so if we don't find the problem in the file, the next step will be to make one - or to ask this question to the Mac people in the Inkscape devel mailing list or devel IRC channel)

You can also try if an experimental build from here:
https://launchpad.net/~suv-lp
might help with the problem. Unfortunately, there's no support for those currently.

Do I understand correctly that Inkscape was functioning properly in the past? Or is this how it worked from the first time you installed it?

I can see that is indeed a serious problem!

It reminds me a little bit of the option that the Pen tool has, to only draw 90 degree angles. Of course it should not affect any tool except the Pen. But it seems so similar, and it certainly would only take a couple of seconds to enable the Pen tool and check the control bar. This button

Not that I really have any technical skills, and I have no idea about this. But it would be interesting if you could install an older version of Inkscape. It can be installed side by side, so you don't have to uninstall 0.91. I would try installing 0.48.5 (the last stable version before 0.91).

If an older version works correctly, at least you could use Inkscape until this is fixed. Or as Moini suggested, the development version.

Did you (intentionally or inadvertently) lower the value for numeric precision (Edit > Preferences > Input/Output > SVG Output > Numbers)?

The default values are '8' for numeric precision and '-8' for minimum exponent. A lower value for numeric precision (≠ number of decimal places) can produce similar output.

Oh ~suv -- happy to see you!

I believe ~suv has solved it!! Yes, I see the numeric precision is 1, and I recall lowering it so that I could more easily manipulate the SVG output by eye. I now use python to do any extractions from the SVG itself.

I have set the numeric precision back to 8, and so far it seems to be back to normal. Many, many thanks!!

Apparently, deleting my ~/.config/Inkscape/.../preferences.xml did not reset this, yet Inkscape restores that file... curious.

Thanks to everyone for their input.

Wow! And a good lesson for those of us who struggle to answer questions about Inkscape.

I don't know if this can be answered in non-technical language, but how does Numeric Precision affect paths? I thought Numeric Precision had to do with decimal places.

Yes, it is curious that deleting prefs file did not reset it!

It's the anchor and control point coordinates in the path. But my question was- why have 8 decimal places when my target pixel resolution is barely 1/10th pixel? Like I said above, I was studying the SVG directly, probably looking at the formulation of bezier curves, and just needed something easier to manipulate in the file.

My guess about maintaining 8 decimals for each coordinate: matrix operations accumulate round-off errors quickly, so I assume the precision is necessary for maintaining accuracy in the transforms. Now that I think about it, the results could look awry in a single scale operation, but a rotate or skew which use cos/sin would simply obliterate any sense of preserving the object's shape. I did notice this happening, but I didn't make the connection.

However, I guess I would be surprised that Inkscape's internal numeric representation is effected by the setting. I assumed it only effected the Output SVG, since it is called that, but in-session coordinates were normal, double-space floating point precision data.

Yes, that's what I was thinking (although I was thinking it much more basically than you, lol). If it's about the SVG Output, why does it affect the canvas. This is probably WAY beyond my understanding. But I guess The SVG/XML is both input and output. Because if you change something in the XML, it changes the selection on the canvas. And if you draw something on the canvas, it creates the XML.

If you're really curious, you could ask the developers, via mailing list or IRC.
https://inkscape.org/en/community/mailing-lists/
https://inkscape.org/en/community/discussion/