Critique of Forrest Gump
The movie chronicles the adventures of Forrest Gump (played by Tom Hanks), a somewhat dim
witted man who lived through the 50s to the 80s.
- Feather in the Opening Scene
The movie begins with a feather falling from the sky and eventually
landing against Gump's right shoe. The scene is one fluid shot, with no
camera changes, so there is little doubt that the "feather" in
the first two images is computer generated, and that the
"feather" in the last frame is real. But what puzzled us is
the seamless transition from a computer modeled feather over to a real
world. Within a span of eight frames, one can see the fading from one
feather to another, but the question is how they removed the real
feather while the fake one was falling.
We chose this scene because our original thought was that they probably
had to track the real feather falling in order to overlay the CG feather
at the correct time. It seems likely, however, that they did not track
the feather but instead did any changes by hand.
- Tang's Analysis
After examining the clip several times, I believe that the visual
editors computer generated a portion of Gump's right shoe.
Specifically, they overlayed the footage with a "shoe" lacking
the feather. Several clues lead me to this conclusion:
- First, the first view of the shoe (not shown above) is from a
distance. The camera does not focus upon it; the viewer cannot
determine if there is a feather there or not.
- By the time one can see the shoe, the camera has slowed down. True,
the computer would need to synchronize with the camera movement, but
this is not a Herculean task.
- Third, only part of the shoe needs to be modeled. Specifically, the
computer would only need to draw the front left quarter of Gump's right
- Furthermore, during the time that it needs to be modeled, the shoe
is not moving -- only the camera is floating about.
- This may or may not be an artifact of the television, but it
appeared to me that the shoe suddenly changes color. This seemed to
coincide with the feather darkening, as the computer model blends into
the real one.
- Finally, the geometry of the shoe appears to alter during the scene.
It looks like the shoe is fatter in the beginning, but suddenly slenders
during the same time as the transition. Again, this may be caused by
sub-optimal viewing conditions or by sleep deprivation.
- Eric's Analysis
My explanation was slightly different. I think the visual editors made
a difference map and extracted the feather from the shoe till the
appropriate time. We both agree that the feather had to be CG.
- First, They made one shot with the feather on the shoe.
- Second they made a second shot (or just the affected portion of a
shot) with no feather on the shoe.
- They then made a difference map and extracted the feather from the
shoe till the point where it lands on the shoe.
- They then computer generated the feather and synchronize it to land
on the shoe right as they take the mask off.
- This seems to be the case for several reasons. First, it seems
to be the easiest way by far.
- Second the feather can be seen on the shoe from a distance (they
forgot to take it out in one of the "far-off" shots).
- Third you can see a slight color change right as the feather lands
on the shoe. This would mark the change from CG graphics to the real
- How it was really done
According to a post on the alt.movies.visual-effects newsgroup, the
"Making of Forrest Gump" segment on the laser disc describes how the
shot was generated:
- First, the feather was suspended in front of a blue or green screen
and filmed twisting and turning in the air.
- The scene was choreographed and shot without a feather floating
through the air, but with a real feather on Hanks' foot. The real
feather can be glimpsed in the final shot during one brief pan where
Hanks is visible in the background.
- The bluescreened feather was digitized and manipulated. A virtual
shot was constructed which matched the original (real camera) shot, and
digitized footage of the feather twisting and turning in the air was
inserted. In addition, the feather was manipulated to move closer to
and further from the camera, since the original bluescreened footage was
at a static distance from the camera.
- Specific frames from the feather footage were pasted together to
form the final twirling path of the feather as it fell. Computer
generated reflections and shadows were inserted when necessary (for
instance, when the feather passes over the car and lands on the man's
- Finally, the feather came down toward Hanks' foot, morphing into the
real feather at the last minute. The real feather was airbrushed out of
the earlier frames by hand, allowing frame-by-frame touchups and
providing a very smooth transition.
There is some argument, especially on alt.movies.visual-effects, as to
whether this constitutes CG or not. Many people maintain that since the
path of the feather was completely manipulated and not natural, this is
CG. Other say that since the original frames of the feather were
digitized from real life, this can't be Computer
Generated. In any case, a large portion of the effect was done
by hand, lessening the digital influence on the scene.
In conclusion, we tended to overanalyze and over-digitize the scene,
when in fact most of the work was not done with finesse, but with sheer
brute force. Only recently have movies started doing complete 3D models
of objects that interact seamlessly with real-life objects.
Critique by Group 1 [the to-be-renamed group], Spring 2000, Mark
Haines, Eric Stevens, and Jason Tang
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Last modified 1 May 2000.
Jason Tang / firstname.lastname@example.org