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GT Module

Skandha4 uses a graphic-terminal driver library to access the workstation graphics. This means that by writing a new driver, you can use all of Skandha4's 3D capabilities on your favorite high performance graphics workstation, even if it doesn't support the SGI-defined OpenGL (Open Graphics Language) that the current driver uses.

This manual is primarily oriented towards doing 3-D raster graphics in Skandha4, so we won't document the older 2-D functions heavily, or encourage their use particularly.

Please note that most 3-D graphics in Skandha4 is done via :DRAW messages to a camera, with very few calls directly to the GT module. (CAMERA does internal calls to GT to generate the image, of course.)

In fact, other than for user I/O via mouse or keyboard, the only direct GT calls a normal Skandha4 application is likely to make are:

;; Initialize to usual mode:
(gt-graphics-mode)                   ; Enter graphics mode.
(gt-set-double-buffering-is-on t) ; Select double-buffered mode.
(gt-set-zbuffering-is-on t)          ; Ask for hidden-surface removal.

;; At beginning of each screen redraw:
(gt-set-color '(0 0 0))           ; Set current color to black.
(gt-clear-viewport)               ; Clear screen to current color.

;; Redraw code here, probably including a (:draw camera ...)

;; At end of each screen redraw:
(gt-swap-buffers)                 ; Make new frame visible to user.

So ... please don't get too excited or depressed over the number of calls supported by the gt!

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