This is a pattern based on a basic shift dress with gathering at the bust one of my employees draped on a dress form. We’re not sure of the exact size of the form as it was old and got recovered, but the measurements are 37-28-38 and we’re calling a size 12. What I hope you find interesting is the method I came up with - a way to code the formulas so that instead of drafting a pattern based on a system, it grades an existing pattern. How I accomplish this is to apply formulas at standard grade points based on the difference between the original draped size 12, and what size we want to grade to.
*I should note that since many of the drafting systems always deal with only 1/2 the pattern, the instructions will always refer measures like the “Chest Scale” which is 1/2 the Chest measurement… so I simply created custom measurements @ChestScale = bust_circ/2, @WaistScale = waist_circ/2, and @HipScale = hip_circ/2. That way it negates having to divide everything by 2 all the time. I simply use it here for continuity.
So here’s the formula for the point at the top of the side seam at the arm hole (B to B1): 9+((@ChestScale-18.5)*0.5)
To break it down … for the size 12 - the width of the back at the bust line is 9"… and based on the bust measurement of 37" the @ChestScale = 18.5". Normally if we were to grade a simple dress like this 2", each side seam will grade in/out 2" / 4 seams or 1/2" at the bust. Here’s the neat trick… if we subtract 18.5 from the @ChestScale for the size 12 we get 9 + 0 x .5 or 9" or no change, but if the bust_cir is 39" and we grade up 2" we get 9 + (19.5-18.5) x .5 = 9.5". If we grade 4" to a 41 bust we get 9 + 2 x .5 = 10"… or if we grade down to a 35", we get 9 + (-1 x.5) = 8.5". By knowing how much a grade point should move up/dn and in/out per 2" grade we can apply this technique at each grade point. With a little more thought one could make use of the nape_b_to_waist_b measure to customize the torso length instead of having to “lengthen or shorten here”,
A final note on this pattern… in the process I came across a few more bugs in Valentina in regards to the seam allowances and notches when using 0" for a “cut on the fold”… there’s a glitch in the seam allowance at the neck line, and the side of the intersection notch at hem line on the front does not show.