Re: _that_ effect.

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Sun, 31 Aug 1997 04:43:28 -0500
>From: P3D Wolfie!  <werewolf@xxxxxxxxxxxxxxxxxxxxx>
>Subject: _that_ effect.

>I've seen an effect used in recent commercials, a car commercial and
>a twisties [australian] commercial. I saw the same effect in a country
>music video.

Which "country" was the music video? :-)

>what happens is that a person or thing is frozen [usually in mid air] and
>somehow the camera pans around the person, although not really 3D, it does
>give a 3D feel. [similar to what people would call 3D in a lot of polygon
>type games].

>so does anyone have an idea of how it's done?

>My theory is that they have 30 cameras or so in half a circle and they all
>fire at once, the frames are scanned into computer and made into an
>animation. 

I first saw that effect in a Rolling Stones video a year or two back - I
*think* the effects were made by "BUF COMPAGNIE" (I think they also had
a hand in the computer-animated "M&M's" commercials we get in the US,
possibly in conjunction with Will Vinton's "Claymation" company). This
year I saw a music video which pushed the effect much further - here are
the "screen credits":
  artist:   bally sagoo
  title:    dill cheez
  label:    tri-star
  director: tim macmillan

This video features full 360-degree rotation, frozen motion of flower petals
tossed in midair, dripping water, and so on. Some of the animations appear to
show at least 170 different viewpoints of the same scene. Several scenes appear
to show traces of sparklers, and at least one appears to show the sparkler
trace, and a moving sparkler drawing the trace at the same time.

The relevance to P3D is the possibility that the techniques used in these
music videos could be applied to stereoscopic still images or animation.
(Come to think of it, I could have tried to watch the video with Pulfrich
glasses.)

My guess would be that they got a fairly large number of cameras (in a
full circle, for the effects I saw), took simultaneous photographs (flash
would be the simplest way to get perfect synchronization of a large number
of cameras), scanned the photographs, then used the information to build up
a 3D computer model (not completely "solid" since all the images were taken
from a single plane), and then the model was used to interpolate between
the images shot with cameras. 

One scene in the more recently seen video showed a woman in midair in the
middle of a jump, inside a room - the whole interior of the room was shown,
but no sign of a camera. I would guess that the woman and the room were
photographed separately, and the images scanned and put together to make
the computer model.

The ability to put multiple images into a 3D computer model could be very
useful in producing "arbitrary viewpoint" stereo pairs. Note, however, that
"perfect" viewpoint interpolation is impossible unless constraints are put
on the choice of subject for the photograph. There is always the possibility
that some important detail is visible only from points of view that are
not covered by the cameras used. (For a music video, there's no reason you
couldn't use imagination to fill in the missing details.)

John R


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