When 
indicates magnification,
the value assigned to TEXTURE_MAG_FILTER determines how the texture
value is obtained.
There are two possible values for TEXTURE_MAG_FILTER:
NEAREST and LINEAR.
NEAREST behaves exactly as NEAREST for
TEXTURE_MIN_FILTER
(equation 3.13 and 3.14 are used);
LINEAR behaves exactly as LINEAR for
TEXTURE_MIN_FILTER (equation 3.15 is used).
The level-of-detail 0 texture array is always used for magnification.
Finally,
there is the choice of c,
the minification vs. magnification switch-over point.
If the magnification filter is given by LINEAR and
the minification filter is given by NEAREST_MIPMAP_NEAREST
or LINEAR_MIPMAP_NEAREST,
then 
.
This is done to ensure that a minified texture does not appear
``sharper'' than a magnified texture.
Otherwise c = 0.