Measure Extention

[Allymelba]

I am interested in using inkscape to draft and store digital patterns for making clothes.  One of the tools I need is to know the length of a curved line.  When I use the measurement extension it gives what is obviously a very inaccurate  result. For example If I  draw a 10 cm line using the grid and then give it an EXTREMELY SLIGHT curve the result is 13 cm. When I have tried longer lines or deeper curves the errors are larger. Is this a bug?

I also have two items I would like to add to the 'wish list'.  Or perhaps someone can tell me how to achieve them.

 First. It would be nice if with the ruler tool I could also have the numbers showing the measurement at each mark. It would be even nicer if this could update/change automatically as you change the length of the line, or the length of the line increases as you deepen the curve on a curved line.  This is very helpful in pattern making as you often need to match to curves.  At times this is actually two sets of 'parallel' curves as you need to match (or know the difference between the two pieces) for the seam lines and the cutting lines.

Second. It would be nice if I could draw a line that stayed the same length even when the line is deformed from exactly straight into a curve.

[Moini]

I don't get this result. Which document template are you using? Have you created a new document with Inkscape 0.92.3, or have you started from a document pre-0.92, or?

Can you share a file?

As I'm not sure I entirely understand everything else:

- have you already discovered the 'ruler' path effect? It will create marks along the path (but will not label them), you need to count, or play with the major/minor step size to measure quickly.

- the measurement tool shows measurements at each crossing of a line (if set to work that way) - is that what you mean?

[Moini]

When we have fully clarified what you mean, the correct place for posting feature requests will be at https://bugs.launchpad.net/inkscape .

[brynn]

Welcome to the forum!

For example If I  draw a 10 cm line using the grid and then give it an EXTREMELY SLIGHT curve the result is 13 cm. When I have tried longer lines or deeper curves the errors are larger.

I don't understand what you mean.  If you have a straight line of 10 cm, and you curve the line without moving the end point, the line naturally becomes longer.  And the more of a curve, or the more number of curves, the longer it gets.  That's how the Measure Path extension is supposed to work.  It measures the actual length of the path, including the curve(s).

If you are looking to acquire the straight line measurement between the 2 end points, then the Measurement tool    is what you need.

For your 2 potential wishlist items:

1 -- It sounds like you essentially need the digital version of a ruler or measuring tape, right?  Rather than the distance between 2 marks, you want the distance at the mark, right?  And in this case, you do want the curve to be measured?  I don't think such a tool currently exists in Inkscape.  The Measure Path extension does measure the curve, but it doesn't put the distance at certain points along the path - only from beginning to end.

2 -- For this, you don't want the curve to be measured.  You only want the distance between the end points of a line?  As far as I understand, this is what the Measurement tool does.

[Allymelba]

I have investigated a bit further.  When I apply the extension "measure line" to line that has been curved I get a result that is probably accurate. However if  I apply the "Path effects RULER" to the line then the "measure line" extension produces what is obviously a wrong measurement. The error varies depending on the units I have chosen for he ruler effect.

See the attached file.
Line practise April 2018.svg
(10.26 kB . 297x210)
(viewed 1393 times)

[brynn]

To create an appropriate comparison, the paths which you apply the Ruler LPE to, need to be converted back to paths before you measure them.  The Live Path Effect changes the path significantly and can't be used as an accurate measure.

So select them, and do Path menu > Object to path.  After that, you should get the right measurement.

I'm not sure why you would want to use the Ruler LPE for your purpose.  As far as I understand, that just creates a drawing of a ruler.  But it's like a real ruler.  Let's say you make a one meter ruler.  Well, it's always a one meter ruler, and you can't stretch it and use it to measure something longer than a meter.

You could make a ruler, let's say the length of your "fabric" or canvas, and reference it as you draw the pattern pieces.  But it doesn't fit with your previous description of what kind of tools you want.

[Moini]

Aha, you're stacking both on top of each other.

Okay, so the trick is to temporarly disable the path effect by clicking on the 'eye' icon. Then the measure extension gets fed the correct path for measuring.

[Allymelba]

Thankyou Moini. I have given that a try and it works well. I can now get an accurate measure.  I will post the 'wish list' in the appropriate forum.

[Moini]

You're welcome!

Do you sew from your own patterns that you make in Inkscape? If so, there's a group of people collecting interesting user projects which produce real-world items.

Brynn's a member of them and would probably be happy if you could share a picture of something that has turned out nice / cool / interesting / special ;-) (and I'm always curious, too).