Division and nodes

General discussions about Inkscape.
User avatar
Espermaschine
Posts: 892
Joined: Thu Jun 05, 2014 9:10 pm

Division and nodes

Postby Espermaschine » Wed Apr 06, 2016 2:19 am

This is something i noticed earlier: performing a Division with circles, creates a huge amount of nodes.
Is this perhaps some kind of bug ? Why cant Inkscape preserve the four nodes for a circle when i perform the boolean operation ?
.
Attachments
Nodes_Circles_Division.jpg
Nodes_Circles_Division.jpg (107.15 KiB) Viewed 1069 times

User avatar
brynn
Posts: 10309
Joined: Wed Sep 26, 2007 4:34 pm
Location: western USA
Contact:

Re: Division and nodes

Postby brynn » Wed Apr 06, 2016 3:16 am

I don't know why either. But a LOT of Inkscape tools and features add all kinds of extra nodes, sometimes double or tripled up. And how it decides to throw in cusp/corner nodes along what it clearly a smooth curve, I don't know. I used the Paint Bucket tool the other day, and found 8 nodes, all piled up on one spot!

This issue is so pervasive throughout Inkscape, I'm tempted to think it's unavoidable and unfixable. But it would be nice if extra nodes didn't get added.

Although I see what you mean! Division with anything from the Ellipse tool does seem to add super-excessive number of nodes. Maybe it could be a bug. Did you search on Lauchpad?

User avatar
Espermaschine
Posts: 892
Joined: Thu Jun 05, 2014 9:10 pm

Re: Division and nodes

Postby Espermaschine » Wed Apr 06, 2016 3:33 am

brynn wrote:found 8 nodes, all piled up on one spot!

This one is especially annoying. And when you try to merge two nodes, afterwards the curve is all wrong.

Did you search on Lauchpad?

No i didnt. I reserve that and interaction with the olympians to other, more capable folk.
Moini inspired me to report (or add) to a bug, and afterwards i deleted my account.

User avatar
brynn
Posts: 10309
Joined: Wed Sep 26, 2007 4:34 pm
Location: western USA
Contact:

Re: Division and nodes

Postby brynn » Wed Apr 06, 2016 3:51 am

I recently found a trick to handle the double and triple nodes issue, without changing the curve. At least this works for me. And it works, no matter how many nodes are there. It seems to automatically get rid of most of them. I couldn't explain why.

Anyway, do a selection box around the stack of nodes, then either "Break path at selected nodes" or "Delete segment between selected nodes". Then "Join selected nodes". After you break the path, the last 2 nodes stay selected, so it's just 2 clicks for the whole thing. 3 if you count the selection box.

You don't have to have an account to just search at LP.

Lazur
Posts: 4717
Joined: Tue Jun 14, 2016 10:38 am

Re: Division and nodes

Postby Lazur » Wed Apr 06, 2016 3:56 am

You mention four nodes, while from 0.91 circles are converted to 8 noded paths? (Maybe that also has to do with precision and size settings.) Circle objects weren't even present before.

On the boolean problem, it is common behave of segments over eachother.
There is an "ideal line" you see on screen, while in reality the Bézier path can never match it.
And, if you have the same "ideal line" drawn on top of each, with different start/end nodes, they differ from that shape almost by zero, yet that differences are different on each.
Making the operator behind the screen scratch their head, and choke on calculating the differences between the two.

A trivial example -draw a circle, duplicate it, rotate the duplicant and add them together.

You see many nodes added? That's because the result is computed right and there is no action taken like -"if the result would get rubbish, interpolate the resulting segments instead". Which action would be hard to code I guess.

I said it is common as I did get it hundreds of times working with autocad's solid objects (a decade before but guessing it couldn't be changed.)
General solution is avoiding such situations where parts of the objects are at the same coordinates, especially if they are curved segments.
(Or use nurbs, maybe?)

User avatar
Espermaschine
Posts: 892
Joined: Thu Jun 05, 2014 9:10 pm

Re: Division and nodes

Postby Espermaschine » Wed Apr 06, 2016 4:06 am

brynn wrote:I recently found a trick to handle the double and triple nodes issue, without changing the curve.

This for stacked nodes, right ?

I mean they have to be on top of each other ?

Lazur URH wrote:You mention four nodes, while from 0.91 circles are converted to 8 noded paths?

Not sure if im following but in my IS version and the devel i have on my machine, a circle converted to a path still has only 4 nodes.

User avatar
brynn
Posts: 10309
Joined: Wed Sep 26, 2007 4:34 pm
Location: western USA
Contact:

Re: Division and nodes

Postby brynn » Wed Apr 06, 2016 4:25 am

That trick works if they are exactly on the same spot, or if they are not quite on the same spot. But if the nodes are not all exactly on the same spot, there will be a small change when the nodes are joined. Usually it's not noticeable when nodes are very close, but not on top of each other. But the further apart they are, the more you will notice.

Oh ok, I just did some testing, with nodes that are nowhere near each other. The trick only works if you use "Delete segment between nodes". It gets rid of all the extra nodes in between, and joins the outer of the selected nodes.


Return to “General Discussions”