Every pixel is identical in the following scene:

// +A0.1 +R3
camera {
 location -z*5
 look_at 0
}
plane {
 -z,0
 pigment {
  rgbt <2,1,1,.5>
 }
}

yet, when rendered with AA and Output_Alpha=on, every pixel is supersampled
(check the stats, it says 9 samples/pixel).

According to "5.2.6.4  Anti-Aliasing Options" in the docs, a pixel is
supersampled if

abs(r1-r2) + abs(g1-g2) + abs(b1-b2) > threshold

(where r1 and r2, etc, are the colors of adjacent pixels.) It seems to me
that the logical extension of this, when outputting alpha, is:

abs(r1-r2) + abs(g1-g2) + abs(b1-b2) + abs(a1-a2) > threshold

where a1 and a2 are the levels of transparency of each pixel. But it seems
that the implementation here is that any partially transparent pixel is
supersampled. This could be horrible in a scene with something like
slow-rendering clouds when alpha output is on.

Version 3.5.beta.RC1, win98, pentium 3 (900mhz), 256MB.

- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]

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