AlphaBuffer.txt

Setup
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blendfunc(zero, srcalpha) -> (0) * srca + (srca) * dsta = srca * dsta
or
blendfunc(dstalpha, zero) -> (dsta) * srca + (0) * dsta = dsta * srca

eg. srca = 0.25, dsta = 0.8; result = 0.25 * 0.8 = 0.2

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Comeback??
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blendfunc(one-srca, one) -> (?) * srca + (?) * dsta = ?
eg.                      -> (?) * 0.25 + (?) * 0.2 = 0.8

Doesn't seem to be possible. :(

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Here's an idea (that needs more thinking on):
-render the players first, set the alpha buffer to appopriate value.
-such that when you render the ground on top, it covers up the players
 that are hidden and blends with the ones that are (semi-) visible.
-meh... I didn't get anywhere with it (maybe I didn't think enough).

Another idea (I think it might be doable):
-render the entire ground first.
-then render the invisible zone on top of the scene, making it darker,
 and filling in the alpha buffer at the same time (use stencil buffer
 to prevent overdraw - possible conflict with smoke grenades?)
  A) invizible zone darkening:
      colormask(1,1,1,1)
      blendfunc(zero, srccolor)
      color(0.5, 0.5, 0.5, 0)
      stencilwrite(set 1)
      stenciltest(equal 1)
  B) smoke grenade darkening:
      colormask(1,1,1,1)
      blendfunc(zero, srccolor)? <- unsure; will be using a texture
      color(0.5, 0.5, 0.5, 0)?
      stencilwrite(off)
      stenciltest(equal 1)
-then render all objects on top using alpha buffer blending to prevent
 them from appearing in the hidden areas (potentially use 2 passes for
 transparent objects, first pass to set alpha buffer accordingly, 2nd
 pass to actually render the object)
  A) opaque object:
      1st pass -> colormask(1,1,1,0)
                  blendfunc(dstalpha, one-dstalpha)
  B) transparent object:
      1st pass -> colormask(0,0,0,1)
                  blendfunc(zero, srcalpha)
      2nd pass -> colormask(1,1,1,0)
                  blendfunc(dstalpha, one-dstalpha)
-the stencil buffer conflict with smoke grandes can be overcome by
 turning off the stencil-write when drawing smoke grenade darkening
-BIG PROBLEM: this method still suffers from the inability to reset the
 alpha buffer back to its previous state after rendering a transparent
 object. This only affects overlapping objects, but still is a big prob.