A
Alpha Channel (or Alpha Pass)
A computer image file contains color information, RGB (or red,
green, & blue), and an alpha channel. The alpha channel
contains compositing information such as the degree of
transparency. The alpha pass is a black and white rendering wherein
the object to be composited appears as white against a black
background. If it is solid white, the object will cover the
background image in the final composite. If it is semi-transparent,
it will composite as semi-transparent in the final composite (with
the background showing through).
Animatic
A rough animated preview of a scene. If a sketch is a test for a
painting, an animatic is a test for a scene; even the objects being
animated are only rough approximations of the final models. An
animatic can be thought of as a moving storyboard.
Aspect Ratio
The ratio of the width of an image to its height. An aspect ratio
of 2:1 would produce an image twice as wide as it is high.
Television has an aspect ratio of 1.33:1. Panavision is 2.35:1.
B
Background Plate (or Element or Image)
The image or series of images over which another image is to be
composited. A typical example would be the stars in a space movie.
The stars are filmed (or created), then those images are used as a
background for the spaceships.
Bitmap Image
An image which is created by assigning color and brightness
information to each pixel.
Blue Screen/Green Screen
A blue (primary blue) backing against which an actor or object is
photographed. This exposes only the blue layer of the film emulsion
(in that area), making it easy to separate the actor for future
compositing. Green is used most often when the element being filmed
is a person: green is easier to remove without affecting the flesh
tones of the actor.
Bump Map
A texture applied to a surface in CGI which gives the appearance of
a dimensional surface. It does not actually alter the geometry of
the object, it merely gives the appearance of doing so. For example
a bump map or ripples applied to a flat plane will look like 3D
ripples when viewed from above, but when viewed from the edge of
the plane, the plane will still be flat.
C
Child/Children
A computer animation term that refers to an object or other item
which is attached to another object (the "parent") and inherits its
motion from it. If you pick up a ball, the ball becomes a child of
your hand. See also "Hierarchy" and "Parent."
Color Balance
When the color from all elements in a shot match so they look like
they were photographed as one. Care must be taken to use the same
color lighting for all of the elements. For example, if the
background plate is that of a setting sun and you are compositing
in an actor in the foreground, the hue of that foreground plate
should match the warm yellowish colors of the background.
Color Channel
Each of the red, green, blue, and alpha components that make up the
color, brightness and degree of transparency of a pixel.
Color Depth (or Bit Depth)
The number of possible colors available for rendering or viewing.
Color depth is determined by the number of bits allotted to each
pixel, and the more bits, the more colors will be available. 4 bit
has 16 colors; 8 bit has 256 colors; 16 bit has 65,000 colors; 24
bit has 16.7 million colors; 32 bit has 16.7 million colors and an
alpha channel with 256 shades of gray. Color depths can also be
thought of as the number of bits per channel instead of all
together. For example, Cineon is 10 bits per channel. SGI
RGB is 8 bits per channel, for a total of 32 bits. So in this last
example, there are 256 shades of red, 256 shades of green, 256
shades of blue, and 256 levels of gray in the alpha channel.
Composite
A composite is a merging of two or more images (elements) into one
final image, or the act of doing that. For example, you may have
footage of an actor, footage of an alien planet surface, and
footage of a spaceship. These will all be layered (composited) onto
each other so in the final version (the composite) you will see the
actor standing on the alien planet with a spaceship in the
background. In the days when this sort of thing was done on film in
an optical printer it was commonly referred to as
"superimposing".
D
Depth of Field
The range of focus around a subject. For example, the actor is in
focus, but the sign in the back of the store is out of focus. Or
the phone in the foreground is out of focus but the actor in the
background is in focus; when the phone rings, the focus is adjusted
to bring it into focus, throwing the actor out of focus. In
photography, Depth of Field is a function of lens focal length and
aperture (F-Stop).
Digitize (3D)
To bring a 3D object into digital form. There are essentially two
methods for doing this: a laser digitizer, which uses a laser to
scan the object and generate data, or a digitizing pen system. The
pen system uses an special pen whose position on a digitizing
tablet is tracked by the computer using magnetic field
disturbances.
Displacement Mapping
Displacement mapping is similar to bump mapping except for one key
difference, which is that it actually distorts the geometry. A
plane with a rippling displacement map will actually appear rippled
when viewed from the top or the side. The drawback is that it will
only displace an object from its points, so to achieve a nicely
displace surface requires many polygons (and therefore, points). A
flat plane made up of one polygon will not look rippled because the
only points available to move are the four at the edges. However, a
flat plane made up of a thousand polygons can easily be
rippled.
E
Ease In/Ease Out
An animation term describing the characteristics of stopping and
starting. When a person moves their arm, the arm actually "eases"
into the move (overcoming inertia) rather than just jumping into
the move like a robot’s. Likewise, when the arm stops, it "eases
out" rather than just abruptly stopping. Generally, a move starts
out slowly, then speeds up to normal speed, then slows down to
stop. This easing in and easing out is usually very subtle.
Element
An image, or series of images, which is to be combined with others.
For example, a person against a blue screen, a miniature set, and
an explosion. These elements, all filmed separately, will later be
composited.
F
Field
One half of a video image. Televisions display their images by
scanning the image onto the screen using two fields for every
image, each time scanning every other line (525 horizontal lines
total). Computer monitors scan both fields at once, progressively-
-from top to bottom- -which is why they appear to be flicker
free.
Film Recorder
A device that transfers computer images to film. The process is
generally called a "film out" or "filming out".
Film Scanner
A scanner that brings the images on movie film into the
computer.
Final
Generally, a term used for a shot when it will have no more work or
adjustments made other than maybe preparing it for the final
filmout. There are different types of "final" though. There is the
type mentioned above, and there is "motion final" which is when the
animation is locked and will not be changed, and "camera move
final" when the animation for the camera is locked, to name just
two types.
Forced Perspective
A technique used with miniatures or full sized sets (and sometimes
even CGI), which causes the apparent depth to be artificially
exaggerated. This is done by taking advantage of film’s 2D nature
by cheating-- building smaller and smaller as the distance from the
camera increases. Smaller things will look farther away than they
actually are.
Foreground
Loosely refers to an element of a shot which appears closer to the
camera. In compositing, it refers to the element to be placed on
top of the others. The text at the bottom of the screen which says
"Five years later. . .…" is a foreground element.
Frame Grab
A single image captured from a video or film source onto a
computer.
Frame Rate
The rate at which the film/video is shot or will be played back.
Normal speed for film is 24 frames per second. Normal video (in
North America) is 30 frames per second (actually 60 fields per
second).
Front Projection
A compositing process whereby film is projected onto a "front
projection screen" which the actors stand in front of. The screen
is highly reflective (it is made of the same material as road
signs). The image is projected right over the actors, but since
they are not very reflective, and since they are lit with film
lights which overpower the projection on them, it is not seen on
them.
G
Garbage Matte
A matte which conceals unwanted imagery included in the original
photography. For example, the rig holding up a model. Garbage
mattes are also used when the blue screen doesn’t fill the whole
frame. (See "Matte")
Generation
The number of times an image has been duplicated. The original
negative is the first generation. A duplicate negative is a second
generation. Digital images do not degrade when copied digitally: an
image can be copied from computer to computer with no quality loss.
Once it’s on film, of course, a copy of that film would be of lower
quality.
Geometry
Along with mesh, model, and object, this refers to the things you
create with points and polygons in a modeling program. Of
course, it's also a type of math, but in 3D graphics, it's more
often used in terms of objects.
Grading
There are two kinds of grading: in-grade and out-grade. To in-grade
means to take the image data (from scanned film) and convert it
from the 16 bit Cineon format to an 8 bit format (such as SGI RGB),
adjusting the color to match a sample "wedge" of the actual printed
film. Out-grading is the reverse: putting the image into 16 bit
Cineon format so it can be recorded out to film.
Green Screen
See "Blue Screen".
H
Hanging Miniature
An effect which uses a model, such as a spaceship, which is placed
directly in front of the camera so as to appear big compared to the
actors who are farther away. Also called a "foreground
miniature".
Hierarchy
A computer animation term that refers to a group of objects or
other items that are set up in parent/child relationships. For
example, the bones in your body are a hierarchy. Your head is a
child object of your neck; your hands are children of your
forearms, which are children of your upper arms, etc. See also
"Child" and "Parent."
I
Image Map
Placing an image over a 3D object in the computer. Image maps can
be bump maps, color maps, diffusion maps, specular maps, etc. For
example, an image of a grid used as a bump map would look like
metal plates on a ship, and an image with numbers used as a color
map would put the identification numbers on it.
Interactive Light
Light which interacts with an object in 3D. For example, an actor
has a flashlight and aims it at the computer generated ship, where
the light can be seen playing on its surface. Or the reverse: the
computer generated ship has flashing lights on it which need to be
represented on the set when the actor is filmed so he’ll end up
being lit by the ship.
Inverse Kinematics (or IK)
A method of setting up character animation wherein the animator can
move the end of a chain of bones or objects and the rest will
follow. For example, grab the hand and pull it up and the rest of
the arm will follow, anchored at the shoulder as in real life. In
"forward kinematics", to raise the hand, the animator would first
position the upper arm, then the forearm, then the hand.
Iteration
Generally used in CGI in the same way that "take" is used on a
movie set. Doing another iteration would be doing another version,
presumably with some requested changes. Used interchangeably with
"version" and "take".
J---
K
Key
1. An electronic method of compositing one
element onto another.
2. The main light in a scene. 3. Short for
"keyframe" (see below).
Keyframe
In animation, a position setting for a character or object. For
example, a if a character is to raise his hand into the air, a
keyframe is set on frame 1 with his hand at his side, then the hand
is raised to its next position, in the air, and a keyframe is set
for frame 15. The computer will then move the hand over the course
of the frames between 1 and 15 from his side to up in the air.
L
Live Action Plate (or Live Action Element)
A shot using actors, as opposed to animation. Shot live on a set,
not an effect.
Lock Off
A shot wherein the camera does not move or rotate at all.
M
Match Move
To use a computer to recreate the camera move from a live action
plate so a 3D element can be added. This can be accomplished by
hand or with software.
Matte
An opaque (or semi-opaque) image that is used to keep an area of
film from being exposed. The film equivalent to the alpha channel
of a digital image.
Matte Line
The visible lines that can appear around an actor or object if it
has been improperly matted (composited) into a shot.
Matte Painting
A painting, traditionally on glass, but now more often done on
computer, which adds to or replaces part of a live action image. An
example is the throne room scene at the end of Star Wars, where
only the soldiers along the aisle are real and the rest are part of
a painting. There are actually two kinds of matte painting; the
standard 2D kind as mentioned above, and a newer version that uses
some 3D elements as well.
Mechanical Effects
Special effects that are done "live" on the set during principal
photography, not added in later. They differ from the similar
"practical effects" in that they are, naturally, of a mechanical
nature (robots, automatic doors, etc.).
Mesh
Along with geometry, model, and object, this refers to the things
you create with points and polygons in a modeling program.
Model
As a verb it means to create something, usually in a modeling
program. (Example: I am going to model a
dinosaur.) As a noun, and along with mesh, model, and object,
this refers to the things you create with points and polygons in a
modeling program. (Example: I just made a dinosaur
model.)
Morph
An effect where one image is transformed into another by changing
its shape and color. Terminator 2 made this effect famous.
Motion Control
A computer controlled camera system which can repeat moves over and
over again with exact precision. The camera moves on tracks. It was
fully developed in the 70’s for use with miniature photography, but
has since expanded to be used for live action composites.
N
NTSC Standard
The video broadcast standard in the North America. It is 525
horizontal lines of resolution displayed in two fields at 60 fields
per second. To be avoided at all cost.
O
Object
As a noun, along with mesh, model, and geometry, this refers to the
things you create with points and polygons in a modeling
program. As a verb it's what you should do when someone asks
you to work for free.
Open GL
A computer display method that allows for objects to be seen as
solids rather than wireframes yet still be manipulated in
real-time.
Optical Printer
A machine made up of one or more projectors and a camera. It is
used to combine separately photographed images onto one piece of
film. Invented in the 1920’s and fully developed in the 1930’s,
this is still the basic idea behind all compositing, including
digital compositing.
P
Parent
A computer animation term meaning that a particular object has
other objects attached to it that will move along with it. The
objects that are attached are called "children", and the whole
setup is called a hierarchy. See also "Child/Children" and
"Hierarchy."
Particle System
A computer application which generates and animates particulate
matter, such as rain, snow, sparks, explosions, flames, bubbles,
etc. The motion of these particles can also be used to drive full
animations. For example, you can set up a particle system to have
particles disperse over a terrain object, then "attach" animated
spider objects to those particles so the spiders will now walk
along the path of those particles.
Pin Registered (or Pin Reg)
A camera, projector, or film scanner which uses pins pushed into
the sprocket holes while the shutter is open to insure that the
film is perfectly steady is "pin registered."
Pixel
Literally, picture element (using "pix" as short for "picture").
The smallest part of a digital image. A pixel is one tiny dot,
similar to the dots which make up newspaper images except that they
are square not round, and there is no empty space in between them.
A standard pixel resolution for film, for example, is 2048 pixels
wide and 1556 pixels high. Television resolution is roughly 720x486
pixels.
Plate
An image element. There are background plates, blue screen plates,
foreground plates, live action plates, etc.
Plug-In
An "add on" computer program which is run from within, and
augments, another computer program.
Polygon
Digital objects are made of polygons. A polygon is a flat surface
area connecting a group of points (or "control vertices" or "CVs").
You can think of this page of paper as being four points, one at
each corner, connected by the paper, which would be a polygon.
Since polygons are flat, to make a curved surface a large number of
small polygons is needed. To think of this in a 2D way, imagine a
stop sign. It doesn’t look round because it only has 8 sides, but
if it had, say, 60 sides, then from a certain distance it would
look round because you wouldn’t see the individual sides. Now, back
to 3D, think of a soccer ball; each of the different colored panels
would be one polygon (except that in a real soccer ball the panels
are curved so imagine they aren’t). Shrink the panels in half but
double the amount of them and the ball stays the same size but
looks rounder. A book could be modeled out of polygons and look
good with only 200 of them, whereas the Titanic model for the film
had over 2.5 million polygons. "Polys" is often used as the plural
form of polygons.
Practical Effects
Similar to Mechanical Effects. Effects which are done live on the
set (explosions, lightning, etc.). Often an effects shot will be a
combination of practical and digital. For example the window of a
car shattering will be done as a practical effect on the set with
actors or stuntmen in the car, but the monster’s hand hitting it
will be done digitally.
Procedural Texture
A computer generated surfacing technique whereby an algorithm is
applied to a surface to give it a certain appearance. For example,
there are procedural textures of wood and marble. These do not rely
on image maps, they are completely computer generated based on
certain user definable parameters, such as grain size, color, etc.
One advantage of procedurals over image maps is that they use less
ram. A disadvantage is that they can take longer to render because
the computer must calculate their parameters.
Pull a Matte
The current CGI use of this term is: to create a matte (or alpha)
from an image for which there is none.
Q
Quickshade
A computer animation rendering method where an animation is
rendered with only basic color information and no image maps or
lighting effects. Quickshade is usually used for rendering
animatics.
R
Rear Projection
An in-camera method of compositing where (typically) an actor is
placed in front of a translucent screen and an image is projected
onto the screen from behind. This can be seen in just about any old
movie where actors are in a car; the road behind them is usually
rear projected,
Record
To output digital images to film. Recording is, of course, the
opposite of "scanning."
Render
The process by which the computer computes and generates the final
image(s) based on all the input and parameters set by the artist.
Somewhat akin to what happens when the director yells "action" on a
movie set: all the setting up, rehearsing, lighting, etc. is
recorded (rendered to film). Or it can be thought of like
paint-by-numbers, wherein the artist assigns the color numbers to
everything in the image and the computer fills them all in
(renders).
Rotoscope
1. To trace the movement of
something. In 2D, the image can literally be traced. In 3D, it is
more a matter of matching the movement.
2. To remove unwanted portions of an image frame by frame. For example, an actor was filmed in front of a cloudy sky but you need it to be cloudless. You would rotoscope the actor, trace around him on every frame so he can be removed from that background and composited over a cloudless sky.
S
Safe Action Area
The area near the edge of the frame which is not subject to the
possibility of being cut off either in projection or on TV by
misaligned equipment.
Safe Title Area
Similar to Safe Action Area, but it allows for even more space at
the edges to be sure that no words are cut off.
Saturation
The degree of color. Bright vivid colors are very saturated;
pastels, less so.
Scan
The process of bringing two-dimensional images, or
three-dimensional objects into the computer. A two-dimensional
image can be scanned with a scanner or traced with a pen on a
tablet or mouse. A three dimensional image can be digitized by
laser scan or by a digitizing pen which uses magnetic fields to
register the X, Y and Z coordinates.
Script Breakdown
A list of shots based on an analysis of the script. It contains
information such as Show Name, Shot Number, Scene Number, Scene
Description, estimated time to complete each shot, estimated costs,
pre-production breakdown, etc.
Shot Card
A sheet containing all the information necessary for an artist to
work on a shot. It contains information such as: Show Name, Shot
Number, Scene Number, a copy of the storyboard for that shot,
artist(s) assigned, due dates, scene setup information, data
location, etc.
Split Screen
A composite technique where the screen is divided into segments
that each have a different image. An example is in every TV show
where a character meets his or her evil twin.
Stop Motion Animation
An effects technique where a model is filmed for one frame, moved,
filmed again for one frame, moved again, etc. King Kong (the
original) was stop motion, as was A Nightmare Before Christmas.
Storyboard
A drawing of the intended scene, looking somewhat like a comic. It
illustrates the character action, the camera movement, etc.
Superimpose
To expose a piece of film more than once for the sake of
compositing two or more images (without the use of mattes). The
images will bleed through each other.
T
Tapeout
Putting shots onto videotape to send to the director or producer
etc. to show progress or get feedback.
Telecine
A machine that transfers film to video, or the act of transferring
film to video.
U
Up Vector
See
Vector.
V
Vector
A direction. For example "up vector" is the line that points
up. In 3D an "up vector" is often used in order to tell an
item which direction is supposed to be up, in case it is rotated in
such a way that its own Y (up) channel no long points up.
VistaVision
A film format wherein 35mm film is run through the camera
horizontally. The image is 12 perfs wide. VistaVision is often used
for photographing background plates in effects work because it
allows full widescreen without anamorphic lenses.
W
Wedge
A wedge is a film sample. This can either be a sample of the
original film, to show what the final should look like, or it can
be a sample of an effect shot which has been filmed out to see if
it matches the rest of the footage. When filming out, several test
frames are done first with different printer light settings to
check which will give the best results, then the full shot is
printed out.
Weight Class Tool
(or Weight Tool)
A Weight Class Tool (or simply Weight
Tool) is an object or collection of
objects that produces static and/or dynamic weights for use with
effects, shaders, and any other messiah
entity that uses spacial weight
values/maps.
Wire Removal
Removing visible support wires or harnesses from a shot using a
computer.
X---
Y--- This space available.
Z
Z-Depth Pass
The Z-Depth pass is an image wherein distance from the camera is
represented in terms of shades of black and white, white being
closest to camera and black being farthest away. It is used, for
example, when compositing images together and it is necessary to
adjust the visibility for something that is a certain distance
camera (like particles underwater), particularly when there is
movement along Z (X is left/right, Y is up/down, and Z is
front/back).
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