- // in formulas:
- // IF there is a (s, sa) for which for all (d, da),
- // s * src(s, d, sa, da) + d * dst(s, d, sa, da) == d
- // THEN, for this (s, sa) and all (colormod, d, da):
- // s*colormod * src(s*colormod, d, sa, da) + d * dst(s*colormod, d, sa, da) == d
- // OBVIOUSLY, this means that
- // s*colormod * src(s*colormod, d, sa, da) = 0
- // dst(s*colormod, d, sa, da) = 1
-
- // note: not caring about GL_SRC_ALPHA_SATURATE and following here, these are unused in DP code
-
- // main condition to leave dst color invariant:
- // s * src(s, d, sa, da) + d * dst(s, d, sa, da) == d
- // src == GL_ZERO:
- // s * 0 + d * dst(s, d, sa, da) == d
- // => dst == GL_ONE/GL_SRC_COLOR/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is a problem for GL_SRC_COLOR only
- // src == GL_ONE:
- // s + d * dst(s, d, sa, da) == d
- // => s == 0
- // => dst == GL_ONE/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is never problematic for these
- // src == GL_SRC_COLOR:
- // s*s + d * dst(s, d, sa, da) == d
- // => s == 0
- // => dst == GL_ONE/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is never problematic for these
- // src == GL_ONE_MINUS_SRC_COLOR:
- // s*(1-s) + d * dst(s, d, sa, da) == d
- // => s == 0 or s == 1
- // => dst == GL_ONE/GL_SRC_COLOR/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is a problem for GL_SRC_COLOR only
- // src == GL_DST_COLOR
- // s*d + d * dst(s, d, sa, da) == d
- // => s == 1
- // => dst == GL_ZERO/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is always a problem
- // or
- // => s == 0
- // => dst == GL_ONE/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is never problematic for these
- // => BUT, we do not know s! We must assume it is problematic
- // then... except in GL_ONE case, where we know all invariant
- // cases are fine
- // src == GL_ONE_MINUS_DST_COLOR
- // s*(1-d) + d * dst(s, d, sa, da) == d
- // => s == 0 (1-d is impossible to handle for our desired result)
- // => dst == GL_ONE/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is never problematic for these
- // src == GL_SRC_ALPHA
- // s*sa + d * dst(s, d, sa, da) == d
- // => s == 0, or sa == 0
- // => dst == GL_ONE/GL_SRC_COLOR/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod breaks in the case GL_SRC_COLOR only
- // src == GL_ONE_MINUS_SRC_ALPHA
- // s*(1-sa) + d * dst(s, d, sa, da) == d
- // => s == 0, or sa == 1
- // => dst == GL_ONE/GL_SRC_COLOR/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod breaks in the case GL_SRC_COLOR only
- // src == GL_DST_ALPHA
- // s*da + d * dst(s, d, sa, da) == d
- // => s == 0
- // => dst == GL_ONE/GL_ONE_MINUS_SRC_COLOR/GL_SRC_ALPHA/GL_ONE_MINUS_SRC_ALPHA
- // => colormod is never problematic for these
-
- switch(src)
- {
- case GL_ZERO:
- case GL_ONE_MINUS_SRC_COLOR:
- case GL_SRC_ALPHA:
- case GL_ONE_MINUS_SRC_ALPHA:
- if(dst == GL_SRC_COLOR)
- return false;
- return true;
- case GL_ONE:
- case GL_SRC_COLOR:
- case GL_ONE_MINUS_DST_COLOR:
- case GL_DST_ALPHA:
- case GL_ONE_MINUS_DST_ALPHA:
- return true;
- case GL_DST_COLOR:
- if(dst == GL_ONE)
- return true;
- return false;
- default:
- return false;
- }
-}
-static qboolean R_BlendFuncAllowsFog(int src, int dst)
-{