My name is David, I am the developer of Touch Embroidery. It is part of the Photo Embroidery family.
At several of the trade shows we would show digitized photographs and vendors and attendees alike would be amazed, by our embroidery. The program could with a several hours of computer time, easily exceed the best digitizers several weeks of work with unparalleled details. It did this with a lot of development work over the better part of a decade, it was and is an amazing product; it required no work from a human digitizer. As an appreciator of the fantastic artistic skill of the digitizers in the industry and, having already made a radical departure from common embroidery, I made another radical departure in the opposite direction. Touch Embroidery was born.
Rather than using vector shapes as a shortcut in Touch Embroidery to lay down a lot of stitches quickly, Touch Embroidery began with an art concept. Building stitches from first principles. Computerized Embroidery has only one type of stitch. Everything else are more of these stitches in special patterns and a considerable amount of graph theory, and linear geometry and some intractable algorithms.
I built Touch Embroidery with artists in mind, and with a very keen belief not to limit the medium of embroidery into those forms which simply relied on laying down stitches as quick as possible. With this in mind, the earliest tools were simple variations of running stitches. And manipulations of those stitches, in a What-You-See-Is-What-You-Get style. Rather than treating embroidery like a paint-by-number scheme, in cumbersome ways. While this is admittedly a powerful set of tools, it's also limiting. You should be able to fill in areas with any type of stitch rather than some predefined patterns and you should be able to fill them in any possible way rather than some predefined ones.
The more I researched linear art, the more I found ways and forms that simply are not captured by the regular forms of embroidery. But, since the most basic element is the stitch (running stitch, straight stitch) I started from there. I added in a few other forms that were not common for embroidery like Fractals and Cyclocycloids even though they are entirely within the medium. You can make them with connected stitches; you cannot make them with Embroidery Software.
Others linear art forms like harmonographs, and guilloche are all entirely possible and plausible as an embroidery. Commonly they are carved onto printing plates and used for things like very fine lines protecting money to prevent counterfeiting (only very high end printers could duplicate such features), but to carve them into plates they are stored as vectors and run through a CNC machine, which is basically the same thing as embroidery but the head of the CNC machine is a sewing machine. However, the guilloche software is completely different. They work with different forms that are not vector shapes, and build fill lines that are not flat fills or satin fills.
Treating embroidery like vectors with stitches is in error. Most software defines a shape then defines a fill for that shape. Fill stitches and satin stitches and every other stitch is just a sequence of running stitches. Tatumi (flat fill) isn't so much a stitch but an algorithm for filling in non-monotone areas with back-and-forth running stitches and applying underlay to various monotone pieces so that a cut is avoided. But there are many ways to do this and usually the best embroiderers can coax their software into doing it the way they want, or offer enough control that digitizers can to avoid the problems this sometimes creates.
With this in mind, as well as the need of some users to quickly lay fill in areas. I spent a very long time considering how to lay down stitches quickly without sacrificing control. You should be able to draw a vector shape and fill it in with stitches, but also alter how it fills in with stitches rather than some of the properties of the fill or the stitches themselves in another mode. The fill tool was my first movement towards these ideas. While overly basic, it allows simple monotone fills without any requirement for closed vector shapes, but rather works through an algorithm called raytracing and a few algorithms I developed for the purpose.
This bottom up approach allows me to build newer methods that work in this lost middle ground between all the power in the world with running stitches and the ability to put needles into fabric quickly of those of traditional embroidery. Many features have been added moving towards this goal, such as the groups and fill tool and many other unseen improvements moving towards building traditional tools out of untraditional piece that don't lose the full potential of the medium.