> The ability of the human eye or a real camera to see infinitely small but
> very bright objects has nothing to do the atmosphere.  It has to do with
> sampling an area compared to sampling points.

Fair enough. But when the human eye does this, it is able to accurately
depict the shape of the object.

In the case of a star, the difference may not be noticable between a
pixel-sized square on your computer screen and the shape of a star in the
sky. As I've said, the 3.6 behavior is useful for those who want to make
stars visible, which is why I'm OK with having the behavior as an option.

But in the case of large bright objects, the image that POV-Ray is providing
looks nothing like what the human eye would see. The human eye would not see
a jagged edge where there is a smooth one, regardless of the brightness of
the object. One's brain would use their eyes to seek out the edge of the
object and portray it as it appears: smooth. POV-Ray 3.6 is not emulating
this (more useful) behavior, in favor of creating an arguably aesthetic
effect in the single case of starfields.

You're saying that the eye has a high enough "resolution" that, if it saw a
star unaffected by atmospheric scattering or anything, despite the fact that
the star would be incredibly tiny, the eye would be able to see it. However,
the eye would display it at the size that it was. POV-Ray 3.6 is taking the
tiny object and blowing it up to the size of a pixel, *by letting it affect
the samples taken around it*. It is also doing this for the edges of larger
objects, allowing shapes that should be smaller than a pixel (like a tiny
triangle cut off of the edge of a sphere) to be blown up to the size of a
full pixel, causing aliasing.

Returning to your statement "It has to do with sampling an area compared to
sampling points," the primary difference is this: the human eye does not
take the samples of that area and average them together and then display the
average value as the value for the whole area. It takes them individually
and displays all objects at the correct size and shape. Obviously POV-Ray
can't do this in its output, since it is limited to pixels. Therefore it
must make a compromise: it can't produce exactly what the human eye would
see, so it must do the best it can to display something that *appears*
correct to the human eye. The compromise in 3.5 appeared correct. The
compromise in 3.6 does not.

The primary usage, purpose, and original intent of anti-aliasing is to
remove aliasing. 3.6's anti-aliasing is failing at this.

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

Post a reply to this message