Graphics Generator

The Graphics Generator (DPS 1561) or GG was a programmable graphics-generating system released by Themiclesian computer developer and manufacturer Data Processing Systems in 1968. Though primarily intended for creating digital graphics and later animations, it instead is best remembered as the first computer to support video games by hardware design. DPS saw extensive use in the publishing and design industry to generate illustrations and diagrams that accompanied text or were publications in their own right. Like many DPS products of the day, it is based on the /1200 series mainframe, though it is not directly compatible with that line of general-purpose systems.

Hardware

Input methods

Structurally, the BLU (binary logic unit) of the GG is not dissimilar to a conventional /1200 mainframe, though its instruction set is heavily modified to include circuitry dealing with graphics rather than complex mathematical operations or manipulative functions (such as multi-step branching). Graphics-related instructions include those that defined geometric shapes, their positions relative to the centre of the display. Through later additions, geometric shapes could also be made to move in a pre-determined or response-dependent manner. Except for input by stored programming, the GG innovated by including a "manual control mechanism", which permitted programmers to manipulate objects on the display with buttons and a light pen, whose input were interpreted by the computer in a manner itself programmable. The results of the input were immediately reflected on the display. To some degree, this permitted non-specialists to operate a computer with very limited introduction and basic intuition.

Graphics & display

The display that the console used was 21" monochrome CRT. However, instead of having an electron gun that scanned lines in a fixed patter, the GG display allows the computer to control its scanning. This meant the computer could intentionally re-scan or under-scan certain places to create contrast, in effect giving greyscale ability to what was supposed to be a monochrome monitor. While the display itself could not distinguish pixels in the modern sense, the computer had a nominal resolution of 512 × 512 dots; that is, all arbitrarily-defined display information had to be completely described within the confines of that plotted plane. As such, if a user defines an irregular shape by giving its outline discretely, the displacement of the topmost and bottommost, and that of the leftmost and rightmost, cannot exceed 512 in either axis; however, if a user defines a circle as an equation with an arbitrarily-given point as its centre, only the centre point needs to be described as a pair of co-ordinates, while the computer automatically generates its perimeter as analog information.

These limitations appear in stark contrast with more modern systems, where generating graphics by discrete plots (sprites) is the norm. The GG was limited primarily by the price of computer memory at the time, and storing discrete plots of any significant size would have made the system unmarketably costly. Through its relatively efficient and developed circuitry for calculating floating-point numbers, the GG could generate well-defined geometric shapes much more quickly than could replicate a raster from memory, which still had to hold program code.