Learning Objectives

1
Learning Objectives

• Raster Methods for Computer Animation
• Design of Animation Sequences
• Traditional Animation Techniques
• General Computer-Animation Functions
• Key-Frame Systems
• Morphing
• Simulating Accelerations
• Motion Specification
• Articulated Figure Animation
• Periodic Motions
• Animation in OpenGL

2
Computer Animation

• Any time sequence of visual changes in a picture

3
Computer Animation

• Real-time animation
• Each stage of the sequence is viewed as it is
  created
• Useful in simulators
• Frame-by-frame animation
• Each frame of the motion is separately generated
  and stored
• Used for movies

4
Raster Methods for Computer Animation

• Double buffering while the screen is being
  refreshed from one buffer, we construct the scene
  in the other buffer
• Raster operations
• Block transfers of rectangular arrays of pixel
  values
• Often used in games

5
Design of Animation Sequences

• Storyboard layout
• Rough sketches
• A list of basic ideas for the action
• Object definitions
• Each participant in the action
• Basic shapes
• Movements to be performed by each character and
  object
• Key-frame specifications
• Detailed drawing of the scene at a certain time
  in the animation sequence
• Generation of in-between frames
• Intermediate frames between the key frames

6
Traditional Animation Techniques

• Squash and stretch
• To simulate acceleration

7
Traditional Animation Techniques

• Timing
• Slow objects are simulated with more frames,
  while faster moving objects are displayed with
  fewer frames

8
Traditional Animation Techniques

• Emphasizing object movements
• Anticipation of coming motion a cartoon
  character can lean forward before running
• Follow-through actions a hat can fly off a
  character that is stopped abruptly
• Staging focusing on an important part of a scene

9
General Computer-Animation Functions

• Managing object motions
• Generating views of objects
• Producing camera motions
• Generating in-between frames

10
Key-Frame Systems

• Generate in-between frames from the
  user-specified key frames (two or more)
• Complex scenes separated into individual
  components called cels

11
Morphing

• Transformation of object shapes from one to
  another

12
Morphing

• Transforming a line segment

added point
key frame k1
halfway frame
key frame k
13
Morphing

• Transforming a triangle into a quadrilateral

added point
halfway frame
key frame k
key frame k1
14
Motion Specification

• Direct specification of geometric transformation
  (transformation matrix)
• Equation of the path
• Bouncing ball

15
Articulated Figure Animation

• Articulated figure hierarchical structure
  composed of a set of rigid links that are
  connected at rotary joints
• Basic technique for animating people and animals

16
Periodic Motions

• Have to be sampled frequently enough (Nyquist
  frequency)

17
Animation in OpenGL

• Double buffering
• glutInitDisplayMode(GLUT_DOUBLE)
• Swapping buffers
• glutSwapBuffers()
• Continuous animation
• glutIdleFunc(animationFcn)

18
Example

• prog13OGLAnimation.cpp