🚀 go-pugleaf

chrisg@cbmvax.cbm.commodore.com (Chris Green) writes: 

> ... render your animation with the knowledge that
> each pixel is (for instance) 35ns later than the preceeding pixel, 
> and that each scan-line is ~63uS later than the preceeding one.

forgive my being brusque: the effects of ignoring the 35 ns temporal
offset between adjacent pixels are absolutely negligible.

even the 63 us temporal offset between adjacent lines is negligible for
all practical purposes: an ever-so-slight temporal slant is introduced,
but no viewer can tell. in fact tube cameras (e.g. vidicons) have the
slant, but modern (frame-transfer) CCD cameras integrate every pixel
during the same exposure interval, and so have no V/T slant.

the effect that is NOT negligible is the exposure time with respect to the
frame time. this has to do with motion blur, but there's more to it than
that. I'm preparing a note about this, but i'll give you the teaser:

  an infinitely short exposure time is optimum to capture motion IF the
  viewer's eye, at the ultimate display device, is tracking the motion.

but if the viewer's eye is NOT tracking motion, say she's locked on the
stationary background, then you should expose for a frame time and
introduce blur, else the temporal content of the moving thing is liable to
generate spatial aliasing. 

for example, if the shot is across a street, and the viewer's eye is
dwelling on a restaurant sign, and a truck with ten-pixel-pitch black and
white stripes speeds by in front at a velocity of ten pixels per frame,
the black and white stripes will alias to become stationary if you've used
an instantaneous shutter. the viewer will judge the apparently-stationary
stripes that appeared for an instant in front of the restaurant to be an
artifact. if you integrate for a frame time, you will get the blur that
the visual system expects.

however if the viewer was eye-tracking the truck, then she will judge it
to be an artifact that the truck's stripes turned gray when it started to
move.

there is no correct solution to this problem. my belief is that the best
pragmatic solution is to integrate for a third of the frame time.

but i can't prove it.

c.

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