Section 17.1.1. Introduction

The first protein structures to be solved were built as wire models. It was only at the end of the 1970s and the beginning of the 1980s that the necessary hardware and software became available to allow crystallographers to construct their models using computers. The first commercially available computer graphics systems were very expensive, and by today's standards rather primitive in their line-drawing capabilities. They were usually controlled by mini-computers loaded with 64k words of memory and removable disks capable of holding 1 Mbyte of data. The limited amount of addressable memory was a severe limitation in software production. Furthermore, each computer graphics system had its own graphics programming library that was totally incompatible with those of other systems. Despite these limitations, the benefits of using computer-graphics-based systems became apparent and they were fairly rapidly adopted by the laboratories that could afford them. The main benefits were not in the construction of the initial model, but rather as a tool in crystallographic refinement (Jones, 1978). Making small manual changes to a model being refined was difficult and time-consuming work, but rather easy to accomplish even with low-powered graphics systems.

The most widely used program of the early days, Frodo, was available on most of the contemporary computer graphics systems. A major step forward occurred with the development of laboratory-scale 32-bit computers with virtual memory operating systems. In particular, the first Digital Equipment VAX models rapidly became the machines of choice in crystallographic laboratories. This allowed the contemplation of real-time improvements in models under construction (Jones, 1982; Jones & Liljas, 1984). Soon afterwards, colour became available in commercial graphics systems. This was much more than a cosmetic enhancement, since colour could be used to convey information vital to the crystallographer, such as main-chain/side-chain status codes for skeletonized electron density (Jones & Thirup, 1986). Unfortunately, there was still no common graphics programming standard, and moving to a new graphics system was a major effort (Pflugrath et al., 1984).

The next major advance in hardware occurred with the development of the workstation, combining the computer and graphics in one package. Although pioneered by Sun, the major player in the crystallographic community was a small Californian company, Silicon Graphics, which rapidly became large. Running the Unix operating system, workstations flourished, but still lacked a graphics environment that was portable between different hardware platforms. This changed when OpenGL was adopted as an industry standard. At the same time, prices stabilized and began to drop in terms of price/performance. Only in the late 1990s have price/performance indicators plummeted with the arrival of PC/graphics-board combinations capable of meeting the expectations of the current generation of crystallographers. The crystallographic workstation on every desk has finally arrived.