WGL_3DFX_GAMMA_CONTROL


NOTE: THIS IS *** NOT *** AN OFFICIAL SPECIFICATION FOR 
WGL_3DFX_GAMMA_CONTROL, SINCE I HAVE BEEN UNABLE TO OBTAIN ONE.
IT IS MY UNDERSTANDING OF HOW THE EXTENSION WORKS IN PRACTICE.

On Windows the gamma ramp for cards with 2d / 3d hardware can 
in general be set using the Win32 functions SetDeviceGammaRamp 
and GetDeviceGammaRamp, as described in the standard MSDN
documentation.

Some 3dfx cards, however, do not support these functions.  As of
December 1999, this category includes Voodoo 1, 2 and Rush.  The 
current drivers for these cards export the WGL_3DFX_gamma_control
extension.  This extension includes two functions:

BOOL wglSetDeviceGammaRamp3DFX(HDC, LPVOID)

BOOL wglGetDeviceGammaRamp3DFX(HDC, LPVOID)

The interface definitions for these functions is the same as for
SetDeviceGammaRamp and GetDeviceGammaRamp.

Note that, as of December 1999:

1) On some versions of the Voodoo 1 drivers you may need to click
on the "link gamma sliders to Glide" button in the driver control
panel to get wglSetDeviceGammaRamp3DFX to work.

2) wglGetDeviceGammaRamp3DFX doesn't seem to work, at least on 
Voodoo 1 and Voodoo 2 cards (the returned arrays always contain 
only zero value elements). However, wglSetDeviceGammaRamp3DFX 
takes a "standard" range of gamma values, so this shouldn't 
matter unless you're trying to store the values present on 
game startup and restore them on exit.