视频图像处理与分析的网络资源.pdf

22/04/98 CAMERON 1 Chapter 1 INTRODUCTION CAMERON is a graphics program designed from scratch with the needs of the crystallographer in mind. It includes manipulation of atom positions using symmetry operators, control over connectivity and gives the user total control over the colour, style and orientation of the pictures produced. 1.1 HOW TO CONTROL THE PROGRAM The program is controlled either by typing commands at the keyboard with the added use of a mouse to pick out atoms and elements if required. The command interpreter is ’intelligent’ and will try to trap as many errors as possible before they are passed onto the program. The error handling routine is user friendly and provides information on the nature of the error and what the correct input should be. There is also an on line HELP facility. 1.2 Command Groups The commands have been collected into groups (twenty-three at present). Each group contains commands and sub-commands which perform related functions or which will act as qualifiers to each other. The command processor will spot invalid combinations of commands and sub commands and enter error mode. Once in this mode the error can be corrected. Command groups are used to decide when the user has finished entering all the qualifiers for a particular operation. The qualifiers are assumed to be finished when a command of another group is entered. For example :- XROT 20 YROT 30 VIEW LINE ALL XROT, YROT and VIEW are all in the same group but LINE (a command that sets the drawing style) is not. When the command processor reaches the LINE command it will then execute the previous commands ie XROT to VIEW. This is useful because it means that th