Object models for computer aided design

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10 def􁪽􋴚􁪽􋵥ed in t􁪽􋵥e scree􁪽􋵣 cocrdi􁪽􋵡ate space (e.o. ro':ation ro􁪽􋴺:i􁪽􋵥es 􁪽􋵥e 􁪽􋵡aVE define􁪽􋵳 serve as a specification for a ?raphic prccessor. The sra;􁪽􋵩ic processor shoul􁪽􋵡 also p:ovide Eorre facili:y to allo􁪽􋵯 operator contrel of the view:􁪽􋴚􁪽􋴺 :ra􁪽􋵳sfor􁪽􋵡a':ion. 􁪽􋵣cr instance, knobs could be used to co􁪽􋵴trcl rotation about x, y, and z in􁪽􋵦 fer tre􁪽􋵳slation. To be csef􁪽􋵬l to the o􁪽􋵥erator, these functio􁪽􋵳s sho􁪽􋵬ld oe abo􁪽􋵴t y __ al􁪽􋵡ays atout the vertical axis of the screen). The 9raphic support for the Fortran based i ::. :_= :. e IT e r. tat ion is described i;"1 Appendix I . This i􁪽􋴻;le􁪽􋵳sntation contains s@veral features th􁪽􋵴t we have not ce3c􁪽􋵩i􁪽􋴚􁪽􋵇G Gere, cwt which are useful for the particular a􁪽􋴻;lication for 􁪽􋴚􁪽􋵩ich that systerr is being used. \\e have s􁪽􋴚􁪽􋵥e i􁪽􋵴to such detail in this cha􁪽􋵴ter, more to attempt to 􁪽􋵲rovide ar. i􁪽􋵳si?ht into the nature of gra􁪽􋵨hio interaction in :te environrrent of object 􁪽􋵯odels than to suggest a corr;re􁪽􋵥e􁪽􋵳sive su;pcrt syste􁪽􋴮. Tte point is that in the context of object rrcdels it is relatively easy to provide flex1􁪽􋵬le ar.G convenien􁪽􋵧 graFtic support which. can vastly sirr;lify the task of wri:i􁪽􋵣c interactive application f cr different