The A-Z Guide to Digital Animation Terminology – Part One: A-M
Whether you’re a hobbyist animator looking to improve your scope of knowledge, an agency exec wanting a clearer idea of the technical terms your contracted animators use, or a freelancing client who has no idea what H.264 is and what it has to do with your small business animation, an A to Z guide is a great place to start filling in the gaps of your knowledge. Today we’ll be focussing on technical terms and how they apply to the world of digital animation, starting with A-M
a: alpha channel
Along with the red, green and blue channels (RGB) which hold the animation’s colour information, the alpha channel is the part of the file that holds transparency information. If you need parts of your exported animation to be transparent (ie. for compositing in a different program), you must save the alpha channel with a file type capable of holding transparency information (see J: JPEG sequence) and appropriate colour settings (see C: Colour Depth and U: Unmatted).
Measured in bits per second (Mbps or kbps), the bitrate measures the amount of ‘bits’ which are displayed in each second of an exported video file. In the most basic terms, a higher bitrate equals higher quality and a larger file size, though much like other export settings the visual difference between bitrates is limited after a certain point by the amount of bits in your source file and the resolution of your export file (see R: Resolution). Bitrates may be constant (CBR) or variable (VBR) with one or two render passes, with a two-pass VBR generally considered the higher quality, but with longer rendering times. Depending on the chosen video file format, you may be able to set a target bitrate and a maximum bitrate, or simply limit the maximum bitrate, in the export settings for your animation. Finding the right balance between a good quality bitrate with smaller file size and less render time can be a trial-and-error process, as individual animations will have different quality requirements and therefore demand different export settings.
c: colour depth
Refers to the setting which dictates the amount of potential colours available for use in the file. For programs that allow colour depth to be set within the working file (such as After Effects), this is measured in 8, 16, or 32 bits per channel (bpc). A higher bpc can mean a higher file size, but offers a smoother colour gradient especially in sequences with glows or lighting effects. Depending on your chosen file format, colour depth can also be set on export, generally measured in millions or trillions of colours. A plus sign (+) next to the colour depth indicates the exported file is capable of holding transparency information (see A: Alpha Channel).
d: duplicate frame
There are several similar but distinct methods of repeating frames in digital animation software, depending on your intent. To ‘duplicate’ a frame in most softwares refers to creating an identical frame (or layer) which can then be manipulated distinctly from the original (eg. to redraw a new frame from one position into a slightly different position). To ‘copy’ a frame refers to cloning the original frame in its exact form which is then updated when either frame is manipulated (similar to a file shortcut, where the shortcut is not a distinct program but a portal to the original). To ‘add exposure’ refers to holding on the current frame artwork for a longer period of frames. [Note: This is a general guide, and terminology can vary from software to software. In the world of 2D animation for example, Toon Boom uses the above terms while Adobe Flash uses ‘copy’ to also mean ‘duplicate’, since there is no direct cloning function for individual frames in Flash.]
f: frame rate
Measured in frames per second (FPS), the frame rate of an animation determines how many individual frames play on screen each second. Common standards are 24fps (for cinema), 25fps (for Australian and European television) and 30 fps (for US television), though web video standards vary depending on the site. Frame rates higher than these standards are used for producing smooth slow-motion video, while lower frame rates tend to appear ‘jerky’ to the eye.
g: graph editor (also known as function editor)
A graph view of the velocity or trajectory of computerised keyframes. As the path of one keyframe to another can be linear, eased in, eased out, or take on any manner of bezier curve velocity, this graph allows for easy viewing and editing of the curves of each keyframe to ensure just the right timing from one keyframe to the next.
h: h.264 codec
Currently a popular export codec for animation and film. H.264 is a lossy codec which considerably compresses the final file size of a video with relatively little quality loss (with the appropriate settings). File types which can be saved with this codec include .mp4 and .mov.
i: inbetweens (and tweening)
In traditional animation, inbetweens refer to the drawings which connect the keyframes (see K: Keyframes) and breakdowns to ensure a smooth illusion of movement. In computer animation, ‘tweening’ refers to the computer-generated process of connecting two digitised keyframes. While tweening can be useful in automating smooth changes in position, scale and rotation, it does not replace the process of drawing necessary inbetween frames for 2D animation.
j: jpeg sequence
Image sequences, such as JPEG or PNG sequences, are a useful export format when an animated scene needs to be transferred to another program for compositing. The rendering process saves a series of images as it goes, as opposed to saving a single large movie file, meaning that the rendering process can be stopped at any time and picked up from the same frame later, and any rendering errors can be fixed easily by re-rendering only the damaged frames. Furthermore, with the right settings image sequences can be entirely lossless in image quality. However it should be noted that file formats which cannot usually handle transparency, such as JPEG files, will likewise not hold an animation’s transparency, while alpha-enabled PNG sequences will (see A: Alpha Channel).
Keyframes mark the ‘major moments’ in an animation. In pose-to-pose animation, the keys are the first frames to be laid out: they map out where the character’s major movements and significant poses sit and give an indication of the timing between each moment. This gives the animator a general idea of where to place the breakdowns and inbetweens (see I: Inbetweens), which are the connecting frames that create a smooth movement between the keyframes. In terms of digital animation software terminology, ‘keyframes’ are the frames where changes in the computer-generated position or trajectory occur, often signalled with a special marker in the timeline (see T: Timeline).
l: light table
In traditional hand-drawn animation, a light table is essentially a backlit tabletop with a clear cover which provides a strong source of light through multiple sheets of paper, allowing for simultaneous viewing through several layers of drawings. The light table concept has carried across to various 2D animation programs: some of which have a ‘light table’ function which allows semi-transparent viewing of non-active layers on the stage, others which simply have easily adjustable opacity sliders for individual layers.
The main function of a mask is to block out or reveal particular areas of another layer. Masks can be set to add or subtract from the attached layer: for example, a circular mask set to add will show only that circular area of the layer, while the same mask set to subtract will show the rest of the layer with a circular hole where the mask is. Multiple masks can be used to intersect each other to create shapes from solids, and other mask settings such as feathering and edge expansion can be used to effectively create vignettes or borders.
Stay tuned for next time as we conclude the A-Z guide to digital animation terminology with Part Two: N-Z.