Phil Clute wrote:
> 
> Being a fairly new pov user I have voraciously toured the many websites
> available,
> viewing nearly the entire povray-webring and all the sites in the povray
> gallery(that
> were still good links). In doing so I have had the enjoyment of seeing a
> lot of great
> stuff. But in my travels(well actually I didn't leave my chair) I
> noticed on occasion
> that some objects are surrounded by a kind of ...well... "aura" for lack
> of a better
> description. Most often(or maybe it's just me) this effect seems to
> accompany spline
> based objects. An example of what I'm talking about can be found at the
> Colefax
> website. The Spline Generator page has two images; both have this
> effect(or maybe
> I should say artifact). If you run the animation it's a bit more
> obvious.
> I am wondering what causes this(mystical enchantment?), and how it can
> be avoided
> ("...don't use splines stupid...").
> 
> --
> ...coffee?...yes please! extra sugar,extra cream...Thank you.

  I think what you are seeing is more related to the jpg artifacts
than any real attribute of using slpines. The Colefax example of
columns had high values of reflection on it that create bright
areas around an object that effect how well jpg compression works.
  The second had a background with a high diffuse value that has
similar problems. You will find these kinds of unwanted traits
happen not only with jpgs but also with animations where the original
24 bit image is compressed and or reduced in color content. There
is not much that can be done abuot it other than plan your scenes
around these limitations. By this I mean don't use areas that abruptly
go from shiny bright to dark on a objects edge. You get the bright
objects saturating the pixels around them and it is more visible when
the surrounding areas are dark.

  Either that or splines got magic. You make the call.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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