zbsize(3G)							    zbsize(3G)

NAME    [Toc]    [Back]

     zbsize - specifies	the number of bit planes desired to comprise the Z
     buffer

C SPECIFICATION    [Toc]    [Back]

     void zbsize(long planes)

PARAMETERS    [Toc]    [Back]

     planes   is the number of bit planes requested to be configured as	Z
	      buffer planes. Only positive values are accepted.	 The default
	      is machine dependent, usually 24 or 32.

DESCRIPTION    [Toc]    [Back]

     zbsize specifies how many bit planes are requested	to be configured as Z
     buffer planes.  The constraints on	planes are machine dependent.  Call
     getgdesc(GD_BITS_NORM_ZBUFFER) to determine the maximum number of bit
     planes available for Z buffer operation.

     zbsize takes effect only after gconfig has	been called.  The number of
     bit planes	granted	for the	Z buffer may not be exactly what was
     requested.	 Call getgconfig(GC_BITS_ZBUFFER) to determine how many	bit
     planes were configured as Z buffer	planes.

     Since Z buffer bit	planes are available only in the normal	framebuffer,
     zbsize should be called only while	draw mode is NORMALDRAW.

SEE ALSO    [Toc]    [Back]

     gconfig, getgconfig, getgdesc, mssize

NOTES    [Toc]    [Back]

     This routine is available only in immediate mode.

     Since most	machines support only a	finite set of Z	buffer sizes, planes
     is	rounded	to the nearest supported size.

     IRIS-4D G,	GT, GTX, VGX, and VGXT models, the Personal Iris, Iris Indy,
     Indigo Entry, XL, XS, XS24, XZ, Elan and Extreme systems do not support
     zbsize.

     The IRIS-4D RealityEngine models support only values of 0,	24 or 32
     planes.  On these models the Z buffer and the depth component in the
     multisample buffer	are independent.  When the multisample buffer is
     requested in the current framebuffer configuration, it is recommended to
     call zbsize(0), as	no Z buffer planes are required.

BUGS    [Toc]    [Back]

     On	the IRIS-4D RealityEngine models the framebuffer cannot	be configured
     to	consist	of 32 Z	buffer planes (or 32 depth planes in the multisample
     buffer) and 8 color planes	for each of the	RGB color buffers
     simultaneously.


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