Fog is initially disabled. While enabled, fog affects rasterized geometry, bitmaps, and pixel blocks, but not buffer clear operations. To enable and disable fog, call glEnable and glDisable with argument GL_FOG. glFog assigns the value or values in params to the fog parameter specified by pname. The following values are accepted for pname : Fog blends a fog color with each rasterized pixel fragment's post-texturing color using a blending factor f. Factor f is computed in one of three ways, depending on the fog mode. Let c be either the distance in eye coordinate from the origin (in the case that the GL_FOG_COORD_SRC is GL_FRAGMENT_DEPTH ) or the current fog coordinate (in the case that GL_FOG_COORD_SRC is GL_FOG_COORD ). The equation for GL_LINEAR fog is f = end - c end - start The equation for GL_EXP fog is f = e - density · c The equation for GL_EXP2 fog is f = e - density · c 2 Regardless of the fog mode, f is clamped to the range 0 1 after it is computed. Then, if the GL is in RGBA color mode, the fragment's red, green, and blue colors, represented by C r, are replaced by C r ″ = f × C r + 1 - f × C f Fog does not affect a fragment's alpha component. In color index mode, the fragment's color index i r is replaced by i r ″ = i r + 1 - f × i f
GL_FOG_COORD_SRC is available only if the GL version is 1.4 or greater.
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glFog: man2/glFog.xml
Fog is initially disabled. While enabled, fog affects rasterized geometry, bitmaps, and pixel blocks, but not buffer clear operations. To enable and disable fog, call glEnable and glDisable with argument GL_FOG. glFog assigns the value or values in params to the fog parameter specified by pname. The following values are accepted for pname : Fog blends a fog color with each rasterized pixel fragment's post-texturing color using a blending factor f. Factor f is computed in one of three ways, depending on the fog mode. Let c be either the distance in eye coordinate from the origin (in the case that the GL_FOG_COORD_SRC is GL_FRAGMENT_DEPTH ) or the current fog coordinate (in the case that GL_FOG_COORD_SRC is GL_FOG_COORD ). The equation for GL_LINEAR fog is f = end - c end - start The equation for GL_EXP fog is f = e - density · c The equation for GL_EXP2 fog is f = e - density · c 2 Regardless of the fog mode, f is clamped to the range 0 1 after it is computed. Then, if the GL is in RGBA color mode, the fragment's red, green, and blue colors, represented by C r, are replaced by C r ″ = f × C r + 1 - f × C f Fog does not affect a fragment's alpha component. In color index mode, the fragment's color index i r is replaced by i r ″ = i r + 1 - f × i f
GL_FOG_COORD_SRC is available only if the GL version is 1.4 or greater.