COMP SCI – WEEK 8
Warm up questions
• Which will rank you higher with Page Rank, having 1 link to your site from Wikipedia, or
having 3 links to your site from the UWO site?
◦ Wiki because it receives more traffic overall than the UWO site
• if we search for the terms “cattle”, “ranch”, “Texas” and we only get pages back that have those
words, what are some of the factors that will make one page show up ahead of another page?
◦ Text – if all of the words are in the title = higher ranking
◦ Link – if words are right in the link
What is animation?
• Asequence of images that create the illusion of movement when played in succession
Why use animation?
• Easier to show somebody how something works then to try and explain it
• also animation:
◦ indicate movement
◦ illustrate change over time
◦ visualize three-dimensional objects
◦ attracts attention
How does animation work?
• Simulation of movement through a series of pictures that have objects in slightly different
• each drawing is called a frame (a snapshot of what's happening at a particular moment)
• required frames per second FPS:
◦ movies on film – 24 fps
◦ TV – 30 fps
▪ 9000 frames for a 5 minute cartoon
◦ computer animation – 12 to 15 fps
Sampling and quantizing of motion
• since each frame is just an image...
◦ each frame is sampled into a discrete sample and each sample becomes a pixel – sampling
• more pixels means better quality
• more samples means bigger file size
◦ each pixel gets assigned a colour, maybe just 2 colours (black and white-->1 bit colour) or
maybe 16 million colours (24 bit colour) – quantizing process
• Q: what else can we “sample” with MOTION?
◦ Frames are chunks as well, the more frames the better quality you get Frame Rate (frames per second FPS)
• frame rate: indicates the playback speed of the animation in frames per second
• 2 types of 2-D animation
◦ Cel animation
▪ also called traditional animation, classical animation, hand drawn animation, frame by
◦ Path based animation
• both types still are made of frames
◦ the more frames per second, the more believable the movement will be
◦ the more frames per second, the bigger the final version of the movies file will be (more
• an animator must HANS draw every single frame!
• To simplify, one background is drawing and then the item that will move is drawn on a clear
sheet of plastic (a cel), one drawing for each frame
• when moving to the next scene, just change the background
• Q: what was the first full length cel-based animated movie?
◦ Snow White
▪ beduted in 1937
▪ over 350, 000 frames
▪ over 1, 500, 000 pen and ink drawings
Path based animation
◦ a starting point for an object (start frame)
◦ an ending point for an object (end frame)
◦ a path for the object to follow
• and then the computer generates all the frames in between (called TWEENING), so that the
artist doesn't have to draw the intermediate frames
◦ what name do we give to the start frame and the end frames?
◦ why is the act of generating the frames in between the first and the last frame called
▪ Because its is in be”tween”
◦ the path the object follows has to be a straight line?
▪ because you can make paths that are not straight
◦ what software allows us to do path based animation?
• the software that generates the frames has features such as:
◦ transitions (fade in and fade out) ◦ repetitions – allows the user to pick how many times the animation repeats
◦ setting the frames per second
• Q: what does fps imply?
◦ The higher the frame rate, the higher the quality
◦ also mean the file size is large because you store more images
What can we do to change the motion?
• If the animation appears too slow, we can speed up the motion by
◦ reducing the number of frames
◦ increasing the frame rate
Slowing down the motion by adding more frames
• assume now that the motion is a bit too fast, 2 ways to slow it down
◦ Way 1: add more frames
▪ keep the frame rate the same
▪ increase the number of frames between the keyframes to stretch out the animation
◦ Way 2: lower the frame rate
▪ keep the same number of frames as original, but stretches out movie
2-D animation terminology
◦ the start and end frames
◦ the act of generating frames between the first and last key frame—creating a “path”
◦ viewing multiple frames at once
• 3-dimension animation involves 3 steps?
Special effects animation
◦ an animation
◦ process of blending together two images into a series of images