# Curves with Formulas

Grace… Yes this is very useful to add/delete points / lines/ splines in a detail, but I’m referring to when working in draw mode where say you add a curve… then later want to add points to use for the control points or reference a line angle to start the curve perpendicular to a seam. Can’t do it. You have to delete the curve (and any subsequent dependencies), then add the curve back in AFTER any other objects you want to reference. It can be a PITA. You have to have an idea ahead of time what steps to take to create a pattern… which again makes it hard to try and fix or modify a pattern.

No, you can add points at a point back in history and use them in the curve. At most, you may have to delete the actual curve and remake it, but even this is mostly not necessary.

Ahh… I got it now… good to know, but of course I’ve discovered yet another bug… You can’t for example add a line between 2 points BEFORE the points exist in the history or you get this:

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Haha, Great! & no, I always check from the end going towards the top to see where the 2 points were added and then go below where the 2nd point was added to create the line & I ALWAYS save my work before using this.

@Douglas, can you report the bug in the issue tracker of github : Issues · valentina-project/vpo2 · GitHub ?

Have you by any chance added a tutorial for this on the Wiki? OR can you help me understand a little better? I’m feeling lost. I had formulas I would use (Say a curve is made with 3 points A,B, C. I would draw lines from A to B and B to C, Then Also the cross points like your X3 and so on. Then the angle for handles at B would be the angle of line A to B plus the angle of line B to C divided by 2. Length would be half the cross point lengths. Close to .55 but not quite close enough) I am finding that my method makes great curves sometimes, but if I change sizing or something they get rough and seam allowances can sometimes go wonky.

Long story short. I understand your handle lengths and how you determine those, but how do you determine the angle for the handles? I’m felling lost on that portion.

@kmf - The wiki provider is not about to change soon!

Hi @caychochang, The handle angles at the shoulders are the angle of the shoulder line plus or minus 90 degrees - (AngleLine_B9_B11-90)

The next handle is the added line going out of it +/- 90 degrees - (AngleLine_B16_x4+90)

The next one is that short connecting line’s angle +/- 90 degrees - (AngleLine_A22_x2+90)

And the centre one at the side seam is the added line going out of it +/- 90 degrees - (AngleLine_x6_B32-90)

Continue in the same fashion to the other shoulder seam.

So where two blue lines meet a node, use a line connected to the node and where there is a blue line, use the blue line, all with plus or minus 90 degrees to get the handle to go at a right angle to the line.

I’ve got the arm curves good now. Thank you. But I’m also working with a Dart it needs to curve. It doesn’t seem to make sense to have it perpendicular to the lines it is attached too. does anyone have useful formulas for curved darts?

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Sorry I haven’t been around, guys. I’ve been dealing with a lot of serious personal issues, as well as starting a new physically demanding job, and I just don’t have the time or energy to be doing much on LF.

Basically, my idea of the ‘ideal curve’ is based on two things:

1. Smooth seams. Unless you are doing something artistic, seams should flow in a smooth line. That is, the angles between two pieces need to add up to 180 degrees. Most will be 90 + 90. (i.e. two right angles.)
2. Smooth curves. If you think about it, a perfect circle (…or section of it) is the smoothest possible curve, with the smallest change in angle over adjoining sections. As I linked to in another post, some mathematical genius figured out that if you multiply the X/Y offsets between two points by 0.55 to determine the control points, you can create a Bezier curve that comes closest to approximating a circle. (i.e. the smoothest curve) That is what the ‘X’ construction points in the above diagram are for; by setting the control points as points along the line, it makes it easy to calculate. (It occurred to me later that the short diagonal lines in the ‘corners’ should not be used when drafting in LF, as we can set the curves mathematically, and those additional points just unnecessarily increase complexity.) As well, each curve section follows the first rule and meets the next at 180 degrees.

Hope this helps!

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I’ve just started reading this thread. The result of your method looks fabulous. Unfortunately, I can’t load the examples as I must have a later version of the program; I get an error message saying Maximum Supported Version 0.4.8 Secondly, you mention the Wiki/tutorial. Could it be written as pdf with a link to, say, DropBox for download?

Hey @Russell! What version does it show when you click on Help and select About Valentina?

Hi @Russell!

Thanks for you interest in the documentation. Here is an article about how to download a MediaWiki to PDF. If you’re successful at downloading, please share it! If you hit a snag, we’re here to help.

https://www.mediawiki.org/wiki/Extension:PdfBook

Actually you have an earlier version of the program. The 0.4.8 refers to the max pattern ver the release v5+ program will load… which is the ver of the program I assume you’re using?

In other words the pattern was created with a more current test build version of the program. You will need to download the 0.6.0 test build to load the pattern file.

Sorry, folks. I completely forgot to add a link to the tutorial I posted in the wiki.

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Thanks for the prompt reply. I have version 0.5.0.1

You are a star, I obviously misunderstood the warning. Thanks for the help.

Thanks for the help but I did have trouble locating the LocalSettings.php:. I downloaded the zip file without any problems and found the pdfBook folder. However, I’m not a programmer so can’t think of where I’m supposed to move it to.

Thank you, I installed the test build and was able to access the file. Thanks for your help

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