Despite our unwavering optimism and bordering on ridiculous pretentiousness, we were actually rather amazed that we were able to get VP·SQUARED to write anything at all on the whiteboard. From the onset, there were countless nonbelievers, who will remain nameless, but all have been awestruck by the shear power and subtle elegance of the point-to-point drawing capability of VP·SQUARED. We see our results as less of a goal achievement assessment than an evaluation of the process of continuous improvement. A theme that keeps coming up is that of the journey. As with any journey, ours has had its stumbling blocks, its "forks-in-the-road", its "dragons-to-slay", if you will, and of course its "lights-at-the-end-of-the-tunnel." We will now go into some detail as to these various aspects:
Our initial efforts were concentrated on building a mounting for the motors and pen cradle, as well as building a stand-alone programming board with ports. We initially had lofty dreams of a machined mounting for the marker, or should we say markers. A certain teaching assistant filled our heads with notions of tri-color markers mounted in a tetrahedral configuration, with each marker having retraction capabilities. We were young and naïve, and the creative juices blinded us to the ultimate constraints of time and resources. It merely took us a visit to the local mall to bring us down from the stratosphere and back to terra firma (see Breakthroughs, 04.06.01). What we casually called a "makeshift temporary configuration" gradually transformed, in name if not in form, into the glorious structure that would ultimately pass for our final project. Some would call it a curtain rod, a spool of fishing line, two stepper motors, an LCD display, keypad, and a bunch of wires, all bound together with duct tape and solder. We call it a work of art.
In all seriousness, VP·SQUARED has surpassed our wildest dreams. The user interface is remarkable, allowing for the point-by-point drawings, which in turn enables block letter drawing and polygons, as well as polynomial plotting, and ultimately general function plotting such as trigonometric functions. It is entirely menu driven, handles negative numbers, and allows for manual calibration. Which brings us to a few of the shortcomings with regard to the accuracy of the plotter. All the calculations that take place in order to perform the plotting operation (see High Level Design), of which there are a substantial number, depend heavily on the plotter being calibrated correctly and on a the accuracy of a constant scaling factor which amounts to the number of inches of string that are released per rotation of a stepper motor, a quantity which may, in fact, be slightly variable depending on how much wire is wound up. Proper calibration requires that both string lengths start out at the same length, and that this length be equal to the length of the separation between the motors, thus making an equilateral triangle with vertices being the motors and the marker. We tried a few schemes for this, which ranged from primitive in nature, to slightly less primitive in nature. One scheme entailed drawing an arc from each motor and marking the intersection, a clever method indeed, but also difficult. Another method was to let one string out to the desired length as measured by ruler and mark the string at that length, then do the same for the other string. This method proved convenient, but over time the marks became imperceptible on the fishing wire. Alas either method gets us a calibration point that is "good enough." The result of not having a perfectly calibrated system is that images become distorted due to exaggerated components in VP-space. Instead of seeing stretching in Cartesian space (i.e. horizontal and vertical dimensions), we observed stretching, in a sense, along arcs.
Other than some minor scaling issues due to imperfections in calibration, the vertical plotter is very quite accurate, has a user friendly interface, has the potential to draw just about anything. It's potential applications are extremely broad, and it's hard to imagine that this device will not eventually touch every persons life in some way. The realization of VP·SQUARED is clearly one of the major turning points in recent history.