"Zeger Knaepen" <zeg### [at] povplacecom> wrote:

>
> The main difference is where you have very bright spots.  Normal 24bit
> images have no way of storing those colors, in POV-Ray-terms, all
> color-components >1 are clipped to 1, hence averaging those images will not
> give accurate results.
>
> Example: let's put it in 1D and black&white.  Let's say you have the
> following frames (every line is a frame)...
>
> This makes all the difference between a realistic animation and a "there's
> just something synthetic about this!"-animation

Oh! I'm seeing the problem now. Thanks for walking me through it with your good
example. Good food for thought. I guess my own blur method will be a
*temporary* one now, until I get to know MegaPOV. :-(

> I suppose screen.inc gives a 1:1 correlation, as long as you're output-image
> is the same size as the input-image.  Be sure though not to use
> anti-aliasing and/or jitter.

Right, right and right. (I actually tried antialiasing while generating some
blurred composite frames--the original images had no AA--as a lazy man's way of
getting AA 'on the cheap.' And it just didn't look very good. Not that I was
really expecting it to...)

BTW, my overall methodology of turning my final POV 'blur' renders into MPEG
animation is to use monkeyjam to gather all the frames together (and to
temporarily see the animation), then use that along with the nice xvid MPEG
codec to generate the animation file, which I then view in Windows Media
Player.  But *somewhere* in this chain, something isn't exactly 'right'--the
final animation viewed in WMP has what looks like slightly increased contrast.
(Or a gamma shift, I'm not sure which.)  I'm betting it's solely the fault of
WMP. (Or else MPEG encoding itself introduces this as a by-product--but I don't
really believe that.) The animation pre-viewed in monkeyjam looks exactly right
(that is, discounting the 'averaging' problem you described.) Right now, I'm
just living with this 'shift', but it's irritating. I've been all through the
xvid app, to make sure I haven't set something wrong there. (It's actually a
menu-driven app where you set up and tweak the codec, which is nice.) Yet I
can't say that I'm an expert with it; I'm surely not!

KW

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