WEEK 5:Computer Animation Techniques

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WEEK 5Computer Animation Techniques
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Introduction

• Animation about movement moving characters,
  moving objects, moving cameras, moving lights and
  moving special effects
  
• In cartoon animation ? the moving image is
  frozen as a series of images on paper or cel,
  can only realized by flicking through image or
  recording them and playing back animation

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• In computer animation, the images are stored
  digitally ? enables them to be manipulated,
  modified and composited with other images with
  reasonable ease
• The real difference, between cartoon and computer
  animation is that a cartoon animator draws each
  image ? to develop moving character computer
  animators models a 3D character once develops a
  script to move or manipulate the model

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• From the previous lectures, we have already known
  that objects and characters are built from
  collections of vertices or CVs represented by
  numbers ? if these numbers are changed, the
  object or character will appear to move or alter
  in size
• Making numbers change ? central to computer
  animation

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Interpolation

• There are many ways of changing one number into
  another, for eg. If we wanted to change 1 into 10
  in 5 steps ? we could require a formula to find
  the number such that when repeatedly added to 1
  resulted in 10
• Instead of using pure numbers, we can use graphs
  to control the speed or how fast our CG
  characters will move(from one number to another)

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Value

100
Fig 5.1 The graph of Value against
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• The graph shows that the change in Value is
  directly proportional to the Percentage () and
  produces the straight-line relationship is a
  linear or first degree graph
• This type of numeric ? second nature to a
  computer, and could easily be used to control the
  position of a camera

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• For eg. If we located a camera at position xyz
  (10,0,20) for frame 1, and xyz (20,10,30) for
  frame 11, so our software could calculate the
  interpolated values between the two positions
• Another example

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Table 5.2 Coordinate values of two camera
positions
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• If we implemented the above animation sequences ?
  we could see that the camera suddenly moves from
  standstill ? moves smoothly to the new position ?
  suddenly stops ? this would look strange as we
  know that is difficult to suddenly move and
  suddenly stop
• It would be impossible to move it from a
  standstill instantaneously ? it requires a
  sustained force to overcome its inertia and any
  frictional forces its same if we wanted to stop
  the particular object, so we would have to slow
  it down over a period of time

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• From a universal law ? states that the
  acceleration of an object is directly
  proportional to the applied force, and inversely
  proportional to the objects mass ?thus large
  forces applied to light objects, result in high
  accelerations

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• Speed
• (mph)

0.6
0.5
0.4
0.3
0.2
0.1
5
10
15
20
25
30
35
40
45
Fig 4.2 Graph of speed against time
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• All this can be interpreted from the slope of the
  graph acceleration is when the graph curls up
  from a horizontal position to a higher speed
  constant speed is horizontal line and
  deceleration is when the graph curls down to a
  lower speed ? means that the graph can be used to
  dictate how objects can be animated

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Function curves

• Very powerful animation tool for the animator
  because they can be applied in all sorts of
  situations
  
• They can be used to slide objects about make
  objects float up and down spin objects about an
  axis move a camera from one position to another
  alter the brightness of a light source or
  control the rate at which a flower opens its
  petals

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Parameters

• Any number used to control or modify the status
  of something is called a parameter Typical
  examples include angels, colors, displacements,
  CVs, positions, surface attributes, velocities,
  accelerations, etc
• The animators set such parameters when modeling
  an object, decorating its surface, or
  illuminating and animating a scene

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• The parameter value can be derived from any
  source such as an f-curve, a program, a file, a
  mouse, or even a real-time electronic device
  
• Parameters can be divided into two sets
• 1- Global parameters
• 2 Local parameters

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• Global parameters have a global impact upon
  animation, and include things such as shading,
  fog, lights, camera, etc
  
• Local parameters control the attributes of an
  object such as color, scale, translation,
  rotation angles, etc

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Keyframes

• Any animation sequence is recorded as individual
  frames
  
• The NTSC video frame rate in the USA is 30 frames
  per second (fps), while the PAL video rate in the
  UK is 25 fps ? in the film industry generally
  employs 24 fps
• Basically, key frame provide the overall
  structure to the animation, the in between frames
  give the continuity and fluidity of movement