Umbra undies: Designer Notes

Umbra is a comfortable and flexible underwear briefs design that aims to be inclusive for as many people as possible.

Umbra is based on some experiments, prototypes and measurements of my favourite underwear.

Umbra is especially designed for diverse users. You can easily add several useful modifications, even if some of them are not directly supported by the software.

Some features of Umbra are as follows:

  • It can be sewn so that no (potentially itchy) seam allowance touches the skin, which helps people with sensitive skin and those with autism. The crotch and side seams are placed on the inside between the front part layers and any elastics on the waist and leg openings can be put on the outside, if so desired.
  • It can be sewn with or without a bulge. You can even draft the design twice, and cut the front lining without bulge and the main fabric front part with one, and you’ll be able to create a front pocket with plenty of space.
  • Rise, back exposure, front exposure and gusset width are controlled separately, so you can create e.g. very comfortable thongs with enough room in the front, or many other designs.

Umbra is based on code from Uma by Natalia Sayang and Joost De Cock, but has been heavily modified in its construction and default style. Some key differences are:

  • Umbra doesn’t have a separate gusset part and instead adds lining to the whole front piece.
  • The hip measurements are being taken into account to better determine the waistband size.
  • The height of the underwear is based on the usually more accurate Cross Seam measurement instead of the Waist to upper leg measurement.
  • The positions of the side and crotch seams can be adjusted freely, even with a bulge selected.
  • The back part has a smoother, more comfortable curve and provides greater coverage by default and at maximum.

Be sure to adjust the “horizontal fabric stretch” and “vertical fabric stretch” options according to your fabric. The default stretch values are rather low. If your pattern appears huge compared to store-bought underwear, they probably use much more stretch.


If you wish to adapt Umbra to a swimwear bottom, it should be easy to do so. Simply use swimwear fabric and, if desired, sew on a folded over piece of fabric with two holes instead of a waistband elastic, to create a drawstring.