cmode - sets color map mode as the current mode.
cmode instructs the system to treat color as a 1-component entity in the
currently active drawmode. The single color component is used as an
index into a table of RGB color values called the color map. Because
color map mode is the default value for all GL framebuffers, it can be
called in any of the framebuffer drawmodes (NORMALDRAW, PUPDRAW,
OVERDRAW, and UNDERDRAW). To return the normal framebuffer to color map
mode, however, you must call cmode while in drawmode NORMALDRAW. You
must call gconfig for cmode to take effect.
While in color map mode, a framebuffer is configured to store a single
color index at each pixel location. The framebuffer is displayed by
continually translating color indices into RGB triples using the
framebuffer's color map, a table of index-to-RGB mappings. The red,
green, and blue components stored in the color map are used (after
correction for monitor non-linearity) to directly control the color guns
of the monitor. Colors and writemasks must be specified using color
map-compatible commands such as color, colorf, and writemask.
Many advanced rendering features, such as texture mapping, polygon
antialiasing, and fog, are available only in RGB mode. Color map mode
lighting, while functional, is substantially less robust than its RGB
Since cmode is the default, you do not have to call it unless the normal
framebuffer was previously set to RGB mode.
color, drawmode, gconfig, getdisplaymode, getgdesc, multimap, onemap,
Color map mode is available in all framebuffers of all hardware
configurations. getgdesc can be used to determine how many bitplanes in
each of the normal, popup, overlay, and underlay framebuffers are
available in both single and double buffered color map mode.
This routine is available only in immediate mode.
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