How to slash and spread a pattern with move and rotate?


I am having a problem to understand how I can open the hem of my pattern.

I made a sketch of what I try to achieve.


y + (y/2) should be x/2

I trie different options, but currently I am just completely confused , how and what I need to rotate and move by what angle so that the left part comes down just the amount needed to open up the hem.

On a sidenote, I have some pleats on the neckline, hence I don’t want to cut through the entire pattern, but just somewhat below the armhole.

Thank you so much.

Regards Éva

OK maybe I have it.

  1. Mark where y ends, draw a line up to the rotation point and rotate the right part so that it meets the angle.
  2. This will obviously make the side go over the upper part of the pattern. So now I select all points on the lower part and move it down until it meets the original side point.
  3. Finally I can add the missing half y to the right.

If there is a better way, I’ll be glad to hear it :grin:

Thanks Éva

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Hi @Evica

I would use the side seam as the pivot point and mark the distance to be opened at the bust. Add a dotted line from the pivot point to the new point created for the angle direction: image

And then use the Rotation Tool to rotate the points R11, R10 & A2 using the AngleLine_PivotPoint_Y

Add a new point at the lowered Waist Line and draw in the new lines or curves:


The secret is in choosing your pivot point carefully depending on whether you want to just open up or to open up in one place and close up in another. :slight_smile: In this case, you want to open up and add to the bottom and the width.

However, your method should work, too :smiley:

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Hi Grace,

thank you so much for your response. I was thinking about your solution, but I think I would get a different result, as basically I don’t know yet how much I need to come down. The hem will be gathered, and I want the ratio to be 1.5. I tried it the way I wrote and I think I have an acceptable result, but I checked how much the pattern came down to allow for the opening and the distance wasn’t y.

But I appreciate your response :slight_smile:

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Yes, that distance is actually X/2=Y, and Y/2 - (X/2)/2 - so that is the distance that you want to move the pattern outwards and downwards. I just used an amount in the Y position, but you can put in your formula as (X/2)/2.

What it does is it moves the side seam outwards by the amount specified and adds the space to the bustline, thereby increasing the length at the waistline.

@Evica Background info: We’re going to use trig. Don’t worry, we’re here to help make it easier!

Step 1: Rotate points A4, A5, and A3 around point A1 by angle
radTodeg( 2 * asin( (y/2) / (2 * Line_A1_A3) ) ) using the Rotate tool. This finds the central angle given chordlength and radius. Original formula is sin(theta) = opposite/hypoteneuse, but only for half the chordlength, so we have to multiply by 2 then find the arcsine then convert to degrees etc. Don’t worry about it :wink: We really need a tool that does this easily.
If typing in asin gives you errors, click on the f(x) symbol and select the Functions radio button then select asin from the list. This example we use 3 instead of your (y/2):

Step 2: Move the center section down.
a. Draw point A8 with Point from X and Y, using A4 for vertical line and A4a1 horizontal line.
b. Then draw a line from A4 to A8 using the Line Between Points tool.

c. Use the Move tool to move Points A, A2 and A5 down length Line_A4_A8 at angle 270 d. Draw lines between your new points with the Line Between Points Tool

We could have moved the center section down and over to meet up with A4a1, but then we would have had to draw a new center line. Both approaches yield similar results.

Let us know how this works for you! HTH


wowww ! A degree in math is needed to use Seamly2D ? :rofl: :crazy_face: Give me an aspirin please :rofl:

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LOL, now you see why I use the other way :slight_smile:

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Wow, both methods look great. I will test it out and let you know the results :blush:


@Vice-Versa We’d like to add some new Operations tools because aspirin is not a patternmaking tool!