If you’ve ever visited a Disney theme park, or if you happen to be a fan
of B-rated films from the 1950’s, then there’s a good chance that you have been
tricked by the illusion of forced perspective; A technique that employs visual and psychological
cues to make objects appear larger, smaller, closer, or farther away than they really are.
Examples of forced perspective can be found just about everywhere if you have a sharp enough eye,
from ancient architecture in Greece and Rome, to modern photography and blockbuster films.
It is also used extensively at many theme parks and tourist destinations,
but especially at the Disney parks where Imagineers use just about every trick in the
book to increase the level of immersion. Forced perspective allows them to build
unbelievable structures that would otherwise be impossible, or at least too impractical
to construct in reality, and it’s a technique that Disney has mastered over the past 65 years.
There is definitely a fine art to creating good forced perspective,
however it is also something that is heavily grounded in math and science.
This is the part that I mainly want to focus on in today’s video, and once we have an understanding
of the underlying principles, we will then use them to explain why some instances of
forced perspective work so well at Disney, and why others don’t really work so well.
To start things off, we should begin by taking a look at the different ways that humans perceive
depth, which is something we have become quite good at through many years of evolution.
Like many mammals, humans have two front-facing eyes that provide us with stereoscopic vision,
meaning that we are able to view the world in 3-dimensions by interpreting
images from two slightly different angles. When both eyes are focused on the same object,
our brain can use the difference in perspectives to estimate how far away it is
by using a process called triangulation. This is basically just a trigonometry problem
where we can solve for the length of the triangle using the distance between our
eyes and the angle of each image, however our brain does this subconsciously in real time.
The ability to perceive depth in this way is commonly referred to as stereopsis,
and it allows us to estimate distances with a high degree of accuracy.
It is also the exact same concept that tricks our brain into seeing depth when watching 3D movies,
because the special glasses allow each eye to view a slightly different image.
Another way that humans perceive depth is called convergence,
and this is pretty similar to stereopsis, however it is based
on muscle sensations rather than visual cues. When an object is placed relatively close to us,
our eyes tend to converge inward so that they can both focus on the exact same point.
This movement is controlled by extraocular muscles that are attached to each eye,
and our brain can sense how much these muscles have contracted or relaxed
in order to determine the angle of convergence. That angle can then be used to calculate exactly
how far away the object is by using a bit of trigonometry, again something
that our brain handles subconsciously. Depth perception by convergence only
works well when the angle is relatively large, however, and it becomes practically
ineffective when an object is further than 30 ft because the angle approaches zero.
This can actually be used to our advantage when trying to create forced perspective, because we
can limit the viewer’s ability to perceive depth simply by keeping them more than 30 ft away.
If you want to see just how much of our depth perception comes from stereoscopic vision,
all you have to do is to cover one eye and try reaching around for a few objects in front of you.
You should find that it is much more difficult to judge how far away things are
because your vision can no longer rely on stereopsis and convergence.
Fortunately, the human brain can also use monocular cues in addition to binocular or
stereoscopic cues, which allows us to perceive depth even when one eye is not functioning.
One way that we do this is through the process of accommodation, which involves
the contraction and relaxation of ciliary muscles that control the shape of our eye lens.
When we try to focus our eyes on objects that are far away, the ciliary muscles relax in order to
make the lens thinner and increase the focal length, and when we try to focus on something
up close, the muscles contact in order to make the lens rounder and decrease the focal length.
Our brain is able to sense the degree of contraction, just like with convergence,
and this provides us with an accurate estimate of how far away the object is,
as long as the distance is greater than 6 feet. Another way that we perceive depth with monocular
cues is based on the principle of angular size, which simply refers to the physical size of the
image that is projected onto our retina. The angle that a given object spans on
the retina is directly proportional to the angle created by the light entering the lens,
and it is dependent on both the actual size of the object and its distance from our eye.
This means that if we are already familiar with the size of a given object,
such as a tree, or a car, or anything else that we might interact with on a regular basis,
then our brain can use the angle subtended on our retina to calculate how far away it is.
This method of depth perception always relies on pre-existing knowledge, or at least a visual
reference, but as long as we have a rough idea of either the scale or the distance,
then our brain can estimate the other simply using the angle.
However, since the apparent size of an object changes with distance,
it is also possible to trick the brain by manipulating angular size, which is the
fundamental technique behind forced perspective. By making a familiar object larger or smaller,
it can appear closer or farther away since this would have the same effect on its angular size,
and conversely, moving the object closer or farther can also make it appear larger or smaller.
The relationship between size and distance follows the rule of similar triangles here,
so if the viewpoint is fixed, then we can calculate exactly what the size and position
should be in order to achieve the desired effect. As long as the difference between the actual and
perceived scale is subtle enough, then this trick alone can be enough to make our brain
think that it is real, even when all our other methods of depth perception tell us otherwise.
A classic example is Main Street USA at Disneyland in California, where forced perspective has been
used to make the buildings appear taller. The first floor of each building is basically
normal size at a scale of 9/10ths, however the second floor has been built slightly shorter at
a scale of 5/8ths, and when there’s a third floor, it has been built at a scale of 1/2.
Our brain is generally familiar with the height of a building, and we have the first story of the
façade as a visual reference, so our mind just assumes that all 3 stories are the same size,
and that the upper floors appear smaller because they are farther away from us.
This illusion can be pretty convincing if you’re not actively looking for it, mostly because the
difference in scale is relatively small, and the buildings can only be viewed from the ground up.
It is easiest to maintain forced perspective when you can control the viewpoint and prevent guests
from getting too close, otherwise the illusion can be broken by revealing the true scale.
This is something that is demonstrated by the American Adventure pavilion over
at EPCOT in Walt Disney World, where forced perspective has been used to make
the building appear smaller rather than larger. The façade of the pavilion has over-sized features
like windows and doors that make it appear as a regular two and a half story building,
and I have to admit that it can actually look pretty realistic when there’s nobody around.
The problem here is that guests are free to walk right up to and inside the building,
which gives us a visual reference for its true size.
Our brain is quite familiar with how tall people are on average, so having a bunch of
guests stand directly in front of the building quickly breaks the illusion, revealing that
the pavilion is actually 5 stories tall. Now, not too far away is a perfect example
that shows just how good forced perspective can be when the viewpoint is totally controlled,
and that’s the corridor scene in Tower of Terror at Hollywood Studios.
In addition to the really cool Pepper’s ghost and lighting effects, the hallway itself is
made to look much longer than it really is by sloping the floor, walls, and ceiling.
Because of angular size, parallel lines will always appear to converge at a single vanishing
point, and it’s possible to increase the perceived distance by making the lines converge faster.
Since the size of the hallway decreases linearly along its length, and smaller objects tend to
appear farther away, it creates the illusion that the hallway is nearly 70 feet long,
even though the sloped portion of the physical set is only about 6 feet deep.
Of course, this is only effective when viewed from just the right distance and
angle within a controlled environment, which isn’t really possible for large
outdoor structures that can be seen from all around the park.
Things like mountains and castles tend to push the limits of forced perspective
a lot further as well, sometimes making them appear as much as 50 times their actual size.
The physics of light starts to become very important at this kind of scale, and simply
manipulating the angular size and distance is not enough to make the illusion believable.
When we look at things that are very far away, they often appear hazy and
dull since the reflected light has to travel much further to reach our eye.
This is primarily due to water droplets and other small particles that are suspended
in the atmosphere, because they reduce apparent contrast and color saturation
by scattering photons as they travel through the air.
Water droplets tend to scatter blue and violet wavelengths more than other colors
on the visible spectrum, and so distant objects can also appear to have a blue tint
because more of these photons get directed towards our eye from incoming sunlight.
For the purpose of forced perspective, it can be useful to replicate these natural
phenomena artificially to make it seem like nearby structures are actually far off in the distance.
This technique is commonly referred to as aerial perspective, and it can be illustrated quite
well with a simple animation of a city skyline. Even though this is just a flat 2-dimensional
image, we can create a sense of depth by using dark saturated colors in the foreground,
and lighter desaturated colors in the middle and background.
Stacking the layers on top of each other helps to further the effect because our brain uses
overlapping to perceive relative depth, and placing certain layers higher up makes them
seem farther away because we perceive them as being closer to the horizon.
We could also choose to add a bit of de-focus blur to give the buildings a slight hazy appearance,
and adding some shadows helps to enhance the 3D perspective.
It’s important that shadows in the foreground are darker and more defined,
while shadows in the middle and background should be lighter and softer due to less contrast.
The final technique that really brings the whole animation together is moving
the layers at different speeds to simulate motion parallax, which is the phenomenon
that causes nearby objects to pass through our field of view faster than distant ones.
This is yet another method that can be used to create an illusion of depth,
and it was actually pioneered by Disney with the help of a multi-plane camera
in some of their classic animated films like Bambi and Snow White.
Now, I’m not aware of any physical examples of motion parallax over at the Disney theme parks,
but there are many attractions that use aerial perspective techniques to appear very far away,
one of my favorites being Expedition Everest at the Animal Kingdom.
The artisans and Imagineers made excellent use of color here,
starting with darker tones for the rockwork around the base of the mountain, and then transitioning
to lighter tones for the rockwork higher up. The white snow also furthers the illusion of
scale because we are already familiar with the idea of giant snow-capped mountains,
and it even has some hints of blue mixed in to reduce the contrast against a blue sky.
Overlapping the various peaks and staggering their height helps to create some added depth as well,
and certain faces have been painted with darker colors in order to produce artificial shadows.
If you look at the attraction from just the right viewpoint where it is partially hidden behind
the tree line, then it really does look like a huge mountain range off in the distance, even
though the actual height is just under 200 ft. The only real problem with the forced perspective
is that the lift hill goes right up into the mountains, and so every time a train goes by,
the illusion kind of gets thrown off by giving us a visual reference for its true size.
For comparison, the rockwork over in Cars Land at Disney’s California Adventure uses many of
the same techniques as Everest, however the illusion is more effective because there’s
nothing around to give away the scale. The aerial perspective is also close to
perfect in Cars Land, with Ornament Valley almost having a hazy appearance way at the back, and in
my opinion, this might be the very best example of forced perspective in all the Disney parks.
In addition to colors losing saturation and brightness over large distances,
textures also tend to lose detail and sharpness, and this is something
that was captured very well here with all the different layers of rockwork at varying depths.
Another land that makes really good use of texture for forced perspective
is Pandora back at the Animal Kingdom, particularly with all the vegetation on
the show buildings and floating mountains. The entire area is filled with a variety of
tropical plants that have a lot of color fine details, but up on the mountains,
they’ve mostly used plain mosses and leaves which are meant to look like distant forests.
Conceptually, the idea is that the mountains are so high up that the forests appear very tiny and
faint when viewed from the ground, however there is some debate about whether this and the whole
floating illusion are actually effective. I think part of the problem is that we
don’t have any prior knowledge about how large the mountains are supposed to be,
since they come from a fictional world, and that makes it really difficult to trick our
depth perception by manipulating angular size. Combine this with the fact that guests can walk
all the way around and even under the structure to get an up-close look, and it’s fairly easy to
see why the illusion gets lost for so many. Personally, I can kind of see the forced
perspective if I look at it from just the right angle,
but I’m curious to know, in the comments, whether you can see it and how effective you think it is.
It may not be Disney’s best implementation of the illusion, but it’s certainly not the worst either.
And now, of course this video would not be complete without talking about the
most iconic forced perspective attractions, and those are the 7 famous castles that can
be found at Disney parks all around the world. Some of the castles look very similar to each
other, while others are more unique, but they all share many of the same characteristics that make
them appear much taller than they really are. Just like the buildings on Main Street USA in
California, the first level is constructed at a 1:1 scale, and the upper levels gradually
decrease in size as they get higher and higher. The bottom portion typically consists of giant
stone walls and a grand archway that are intended to be life-size,
or at least as large as we might expect them to be if we have never seen a real castle before, while
the upper portion consists of tall slender spires with lots of intricate architectural features.
The various elements give the design an elaborate and royal appearance, but they have also been
carefully arranged so that it is difficult to distinguish between individual floors.
This helps to keep the height more ambiguous because our mind can’t
determine the scale by counting the number of stories, which is especially important
when viewing the castle from a distance. The upper portion is also thinner than
the bottom and set back slightly so it appears farther away, and it is meant to look like the
stone walls are actually positioned in front of the castle to create an illusion of greater depth.
I find that this effect is most apparent on the original Sleeping Beauty Castle in Disneyland,
where it almost seems like the pink section is part of a separate structure on the other
side of the wall, but in reality, it’s all part of the same building.
The contrast in color and texture also helps to increase the perceived depth here,
and you might notice that the tones gradually get lighter from the bottom to the top,
which furthers the illusion of height. Many of the castles were originally
painted with light pale colors in order to achieve aerial perspective as well,
but lately Disney has been going for more vibrant colors that really stand out and catch the eye.
Unfortunately, this does seem to have a slight impact on the intended forced perspective,
but the castles are so massive anyway that I don’t think too much of the illusion is really lost.
However, there is one other castle that we still need to talk about which doesn’t
have the advantage of scale, and that is the Beast’s castle in the Magic Kingdom.
This is probably the worst instance of forced perspective that you can find at any of the
Disney parks, but it’s a perfect example of what happens when the illusion is pushed too far.
The castle only stands about 20 ft tall on top of the Be Our Guest restaurant,
however it is supposed to look closer to 400 ft, which is 20 times its actual size.
For comparison, Cinderella castle at the end of Main Street is also supposed to look like 400 ft,
but that’s only twice its actual size since it’s already just under 200 ft tall to begin with.
Forced perspective tends to work really well for small to moderate changes in perceived scale,
but it becomes less and less effective as the scale stretched further and further.
On paper, the concept of angular size tells us
that the Beast’s castle and Cinderella castle should both appear the same size,
but in reality, it’s just not possible to fool human depth perception with a miniature model.
I tried to use Photoshop to make the illusion look a little more realistic
by lowering the saturation and contrast, and adding in some blue tones with a bit of blur,
but even the textures and level of detail are not all that convincing from such a close viewpoint,
and it loses any sense of aerial perspective as soon as we go back to the original image.
The castle simply appears too bright and vivid with really harsh shadows, and the
illusion is lost entirely as soon as you see a person or a bird up there as a size reference.
Aside from this, the Disney theme parks are still home to some of the very best forced perspective
illusions in the world, including so many more that I couldn’t get to in just one video,
and there’s really only a few where something might seem a little off.
I’d love to hear which ones are your favorites down in the comments,
as well as which examples you personally find the most and least effective.
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