NAME

zbuffer − starts or ends z-buffer mode

SPECIFICATION

C
zbuffer(bool)
Boolean bool;

FORTRAN
subroutine zbuffe(bool)
logical bool

Pascal
procedure zbuffer(bool: Boolean);

DESCRIPTION

zbuffer starts bool = TRUE or ends bool = FALSE z-buffer mode.  In z-buffer mode, each pixel has an associated z value.  To draw a pixel, the system compares the new z value with the z value already associated with it.  If the new z value is less than or equal to the existing value (i.e., closer to the viewer), then a new color and z value are stored in the bitplanes; otherwise, the color and z value for the pixel are left unchanged. 

All obscured surfaces in objects drawn in this mode are not displayed.  z values range from 0xC000 to 0x3FFF on a 32-bitplane system, and 0x0 to 0xFFF on a 28-bitplane system.  setdepth sets this range. 

z-buffering does not work for lines greater than 1. 

z-buffering is not effective on systems with less than 28 bitplanes.  Because memory bandwidth is reduced on 60Hz monitors, you can improve performance by using blankscreen to blank the screen during z-buffer drawing. 
 

SEE ALSO

blankscreen, getzbuffer, setdepth, zclear Programming Guide, Section 12.1, Z-Buffer Mode

BUGS

A bug exists in the line and point code.  Lines and points are not drawn if the z values are exactly the same as the existing value. 

Version 3.6  —  December 20, 1987