5:42 p.m.
Hi,
I'm after some functionality in Inkscape but unfortunately I don't know
what it's called, but I will try to describe it:
1. I draw a polyline (a path of straight line segments with a few nodes).
2. I use the node tool to grab one of the nodes and reposition it.
Currently in Inkscape when I do (2) the line segments either side of the
node adjust their lengths to accomodate the new position of the node.
What I'm after is where the entire line is treated as if the segments were
*rigid* (i.e. fixed length) and think of the nodes as hinges. So I drag one
of the nodes to a new position, and by virtue of the fixed length line
segments the rest of the line is dragged with the node, to some extent.
For example you could imagine if I had a straight line with two segments
and nodes A/B/C:
(A) --- (B) --- (C)
If I grab (B) and drag it upwards, this is what Inkscape does (on the left)
compared to what I want (on the right):
(B) | (B)
/ \ | / \
/ \ | / \
/ \ | (A) (C)
/ \ |
/ \ |
/ \ |
/ \ |
(A) (C) |
(it renders OK for me in monospace)
On the left, the segments AB and BC are lengthened and A and C remain in
their original positions.
On the right, AB and BC preserve their length, and as a result the entire
line is dragged upwards.
The particulars of exactly how (A) and (C) reposition themselves is not
important to me, as long as they act in a way consistent with AB and BC
having the same length before and after.
1. what is this feature called (so I can ask about it/search for it
better)?
2. Does Inkscape support this? (say I can toggle between the fixed-length
and variable-length modes)?
cheers,
Amy
7:49 p.m.
This is a very interesting idea, but I don't know what it is called and am
fairly certain that Inkscape does not currently support it.
The problem is that there will be some ambiguity as to how to impose these
constraints. For example if you have a line segment with 5 points ABCDE, and
you start pulling on A to make the line longer. Initially you will be able
to deal with this just by adjusting B alone. But at some point ABC will be a
straight line, so you will now have to adjust C as well. So now there is
ambiguity, should you adjust C on the assumption that ABC remains straight,
Or should you adjust both B and C simultaneously to deal with the change in
A? And what happens when the entire line ABCDE is completely straight?
Should all stretching movement now be forbidden or should the entire line
move as a straight line? And when you start to compress the straight line
length by moving A inwards, should you adjust only B, or should you perhaps
move all the points equally to introduce curvature to the whole line?
Anyways, I would be very interested to see if anyone has ever tackled this
problem.
Alvin Penner
--
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http://inkscape.13.x6.nabble.com/joint-and-wire-type-polylines-fixed-leng...
Sent from the Inkscape - User mailing list archive at Nabble.com.
9:29 p.m.
Maybe we could look at it from another 'angle'? This way of reasoning can also be
founnd in programs like SolidWorks (parametric modelling), where it's all about
'degrees of freedom' . Looking at two points in a 2-dimensional plain with a line
between them, there are 4 degrees of freedom(*). Presently, Inkscape doesn't fix any
of these. But you could image that when two nodes are selected, Inkscape would allow us to
partially 'fix' the relation between them. We should be able to tell Inkscape,
for example:
-Node A is always 3 centimetres to the right of node B and 4 centimetres to to the top
or
-Node A is always 3 centimetres to the right of node B, but the vertical position is free
or
-the distance between A and B should always be 5 centimer, but their angle is free (this
situation reflects the idea of the original question)
or
-the angle between A and B is always 36 degrees, but the distance is free.
These relations could be made pair-wise, so also between A and C and B and D. But, the
number of relations should not be larger then the total degrees of freedom.
(*) You can look at this in a number of ways:
(1) two points have both two ordinates (x,y) that can all be set independently, which
makes 2 cordinates x 2 points = 4 D.O.F. .
(2) One point has one set of ordinates, the other has a relative distance to the
previous.
On Sep 24, 2013, at 12:49 PM, alvinpenner <penner@...2467...> wrote:
This is a very interesting idea, but I don't know what it is
called and am
fairly certain that Inkscape does not currently support it.
The problem is that there will be some ambiguity as to how to impose these
constraints. For example if you have a line segment with 5 points ABCDE, and
you start pulling on A to make the line longer. Initially you will be able
to deal with this just by adjusting B alone. But at some point ABC will be a
straight line, so you will now have to adjust C as well. So now there is
ambiguity, should you adjust C on the assumption that ABC remains straight,
Or should you adjust both B and C simultaneously to deal with the change in
A? And what happens when the entire line ABCDE is completely straight?
Should all stretching movement now be forbidden or should the entire line
move as a straight line? And when you start to compress the straight line
length by moving A inwards, should you adjust only B, or should you perhaps
move all the points equally to introduce curvature to the whole line?
Anyways, I would be very interested to see if anyone has ever tackled this
problem.
Alvin Penner
--
View this message in context:
http://inkscape.13.x6.nabble.com/joint-and-wire-type-polylines-fixed-leng...
Sent from the Inkscape - User mailing list archive at Nabble.com.
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1:27 a.m.
Depending on how you plan to apply this, it might be feasible to write a
program in Javascript or Python or whatever to modify an SVG file on the
fly based on some "physics" rules you make up - I think Maarten's email
would be a good starting point for research. I have heard the word for this
before, I just do not remember it.
-Arlo James Barnes
2:13 a.m.
I believe what is being described is similar to 3d model "rigging" - where
you define a skeleton, angles of movement, and lengths of appendages, etc.
On Tue, Sep 24, 2013 at 9:27 AM, Arlo Barnes <arlo.barnes@...155...> wrote:
Depending on how you plan to apply this, it might be feasible to
write a
program in Javascript or Python or whatever to modify an SVG file on the
fly based on some "physics" rules you make up - I think Maarten's email
would be a good starting point for research. I have heard the word for this
before, I just do not remember it.
-Arlo James Barnes
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3:01 p.m.
Cheers - will have a search around rigging/skeleton/degrees of freedom and
see what I can find. (I think 'rigging' was the word I was looking for,
although I want a simple 2d case and inthe case of ambiguity as to how the
skeleton moves when I drag one of the joints, I do not care so much how
this is resolved so long as it "feels" natural.
I suppose one way to address the ambiguity alvinpenner mentioned would be
to pick some (fairly arbitrary) direction along which "gravity" is applied.
Which brings me back to a 2D physics engine, I think).
I am just trying to write an Inkscape extension for drawing crochet
diagrams (!), and there is a use case where you might have a "string" of
stitches laid out into some particular shape an you want to adjust this
shape, keeping the string (and stitches) the same length and size - that
is, each stitch has a fixed size an each stitch is connected to the stitch
next to it. I had the idea of representing the pattern where the stitches
are nodes along a path (that way not only do I get the shape all the
stitches together should make, but the use of a path with nodes gives me
the *order* the stitches are done in so that I can generate a word pattern
from a diagram).
On 25 September 2013 03:13, Chris Tooley <euxneks@...155...> wrote:
I believe what is being described is similar to 3d model
"rigging" - where
you define a skeleton, angles of movement, and lengths of appendages, etc.
On Tue, Sep 24, 2013 at 9:27 AM, Arlo Barnes <arlo.barnes@...155...>wrote:
> Depending on how you plan to apply this, it might be feasible to write a
> program in Javascript or Python or whatever to modify an SVG file on the
> fly based on some "physics" rules you make up - I think Maarten's
email
> would be a good starting point for research. I have heard the word for this
> before, I just do not remember it.
> -Arlo James Barnes
>
>
> ------------------------------------------------------------------------------
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6:24 p.m.
Other Inkscapers might be of better help for your idea, but you can also set 'mid
markers' for paths. Usually, you use start and end markers to create arrows and so on.
But you also put them in evey node in the path. It's even possible to define your own
custom mid-marker, but I believe it requires editing the SVG directly in a text-editor.
On Sep 25, 2013, at 8:01 AM, Amy <mathematical.coffee@...155...> wrote:
crochet
6:50 p.m.
New subject: joint-and-wire-type polylines/fixed length line segments?
On Wed, 2013-09-25 at 11:24 +0200, Maarten van der Velde wrote:
Other Inkscapers might be of better help for your idea, but you can
also set 'mid markers' for paths. Usually, you use start and end
markers to create arrows and so on. But you also put them in evey node
in the path. It's even possible to define your own custom mid-marker,
but I believe it requires editing the SVG directly in a text-editor.
Editing the SVG directly will get you a "cleaner" marker but you can
also use the Object -> Object to Marker command to create custom
markers. See:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Attributes-Stroke.html#Attri...
I think what is required here is the ability to have different markers
along the path such as o-x-o-x-o-x. That is not possible with SVG 1.1.
SVG 2 will allow such patterns. See:
http://www.w3.org/TR/SVG2/painting.html#RepeatingMarkers
Tav
7:20 p.m.
The term for the math is inverse kinematics or IK.
Sent from my iPhone
On 24 Sep 2013, at 18:13, Chris Tooley <euxneks@...155...> wrote:
I believe what is being described is similar to 3d model
"rigging" - where you define a skeleton, angles of movement, and lengths of
appendages, etc.
On Tue, Sep 24, 2013 at 9:27 AM, Arlo Barnes <arlo.barnes@...155...> wrote:
Depending on how you plan to apply this, it might be feasible to write a program in
Javascript or Python or whatever to modify an SVG file on the fly based on some
"physics" rules you make up - I think Maarten's email would be a good
starting point for research. I have heard the word for this before, I just do not remember
it.
-Arlo James Barnes
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10:51 a.m.
Tavmjong: Aye, I need arbitrary mid-markers (can put different stitches
next to each other). I was thinking of either waiting for SVG 2 (that will
take forever I guess) or in the meantime just using Inkscape's connector
functionality to try preserve connected-ness of my paths of stitch symbols.
John Cliff: cheers, will check it out
On 25 September 2013 20:20, John Cliff <john.cliff@...155...> wrote:
The term for the math is inverse kinematics or IK.
Sent from my iPhone
On 24 Sep 2013, at 18:13, Chris Tooley <euxneks@...155...> wrote:
I believe what is being described is similar to 3d model "rigging" - where
you define a skeleton, angles of movement, and lengths of appendages, etc.
On Tue, Sep 24, 2013 at 9:27 AM, Arlo Barnes <arlo.barnes@...155...>wrote:
> Depending on how you plan to apply this, it might be feasible to write a
> program in Javascript or Python or whatever to modify an SVG file on the
> fly based on some "physics" rules you make up - I think Maarten's
email
> would be a good starting point for research. I have heard the word for this
> before, I just do not remember it.
> -Arlo James Barnes
>
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most
> from
> the latest Intel processors and coprocessors. See abstracts and register >
>
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg....
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>
>
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8:41 p.m.
New subject: joint-and-wire-type polylines/fixed length line segments?
On Thu, 2013-09-26 at 11:51 +1000, Amy wrote:
Tavmjong: Aye, I need arbitrary mid-markers (can put different
stitches next to each other). I was thinking of either waiting for SVG
2 (that will take forever I guess) or in the meantime just using
Inkscape's connector functionality to try preserve connected-ness of
my paths of stitch symbols.
One solution would be to have arbitrary connecting points and metrics
between shapes. But when you think about how to make even two simple
paths have a single point that occupies the same point, even outside the
svg spec it gets rather hard to imagine how to do it.
No matter how useful such a thing would be ;-)
Martin,
9:59 p.m.
Isnt this the difference between the select tool and the node tool? Ones modifying the
shape structure, ones modifying its position.
Sent from my iPhone
On 24 Sep 2013, at 11:49, alvinpenner <penner@...2467...> wrote:
This is a very interesting idea, but I don't know what it is
called and am
fairly certain that Inkscape does not currently support it.
The problem is that there will be some ambiguity as to how to impose these
constraints. For example if you have a line segment with 5 points ABCDE, and
you start pulling on A to make the line longer. Initially you will be able
to deal with this just by adjusting B alone. But at some point ABC will be a
straight line, so you will now have to adjust C as well. So now there is
ambiguity, should you adjust C on the assumption that ABC remains straight,
Or should you adjust both B and C simultaneously to deal with the change in
A? And what happens when the entire line ABCDE is completely straight?
Should all stretching movement now be forbidden or should the entire line
move as a straight line? And when you start to compress the straight line
length by moving A inwards, should you adjust only B, or should you perhaps
move all the points equally to introduce curvature to the whole line?
Anyways, I would be very interested to see if anyone has ever tackled this
problem.
Alvin Penner
--
View this message in context:
http://inkscape.13.x6.nabble.com/joint-and-wire-type-polylines-fixed-leng...
Sent from the Inkscape - User mailing list archive at Nabble.com.
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11 comments
8 participants
participants (8)
-
alvinpenner -
Amy -
Arlo Barnes -
Chris Tooley -
John Cliff -
Maarten van der Velde -
Martin Owens -
Tavmjong Bah