Re: percieving fast motion (was: Re: gettimeofday() and clock)

["Adam D. Moss" <adam@gimp.org>]

Steve Baker wrote:
> [Not-Steve-Baker wrote:]
> > Another, simpler idea I had before I stumbled over this article was to
> > approximate the movement the object makes by a series of linear segments
> > each one being as long as the time the frame is displayed. Then you blur
> > it along this line segment while rendering the corresponding frame by
> > drawing it several times (using alpha-blending, of course)

Just wanted to say that Descent 3 does a continuous interpolation of
stars along a line from their old position (at zero intensity) to
their new position (at full intensity) and it's a very pleasing effect
even (or especially!) at low frame-rates.

Hell of a lot easier to do for points than for arbitrary
textured objects though!

An accumulation buffer initially sounds like the 'right' way
to perform the above quoted effect, but then thinking about it
I realized that this probably only adds two useful options:

1) Accumulate (say) 3 time-interpolated frames' worth and display
the result.  Unless you're after a particular 'effect' then
this is probably useless on PCs with high-refresh monitors (that
is to say, just get your new frames to the front-buffer ASAP
instead of accumulating them), but lovely if your display device
is low-fixed-refresh (say 50Hz) but your engine and hardware can
push out (say) 150fps and you have fast-moving scenery.

2) Accumulate the majority of the new frame with a fair pinch of
the previous frame.  In theory this does nothing except simulate
pretty lousy relatively-long-retention phosphor, but I've seen
it used in a few games (Magic Carpet, GTA3) and it's not an
*un*pleasant effect, though I wonder why they bother.

> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net

Is your skeletal animator still alive, Steve?  It looked very
interesting.

--Adam
-- 
Adam D. Moss   . ,,^^   adam@gimp.org   http://www.foxbox.org/   co:3
"Beware the leader who bangs the drums of war in order to whip the
citizenry into a patriotic fervor, for patriotism ... both emboldens
the blood, just as it narrows the mind." -- Julius Caesar