CG MOD 5

MODULE 5: COMPUTER ANIMATION

Definition of Computer Animation

  • Computer animation refers to any time sequence of visual changes in a scene. Changes can include:

    • Object position (translations or rotations)

    • Size

    • Color

    • Transparency

    • Surface texture

  • Common examples include transforming one object shape into another, such as a can of motor oil into an automobile engine.

Applications of Computer Animation

  • Realistic Displays: Essential in simulators for training pilots or heavy equipment operators, where accurate representations are crucial for effective training.

  • Visual Effects: Widely used in entertainment and advertising, enabling exaggerated shapes and unrealistic transformations that capture audience attention.

Designing Animation Sequences

  1. Storyboard Layout: Outlines the action and motion sequence, which can be rough sketches or lists of ideas to visualize the flow of the animation.

  2. Object Definitions: Involves defining objects by their shapes (such as polygons and splines) along with specified movements.

  3. Key-frame Specifications: Key frames represent detailed drawings of scenes at specific times in the sequence, serving as essential reference points.

  4. Generation of In-between Frames: Intermediate frames are created between key frames to smooth out motion and enhance visual fluidity.

Real-time Animations and Frame-by-Frame Animation

  • Real-time Animations: These respond to user input and can change dynamically based on interactions.

  • Frame-by-Frame Animation: Requires separate generation of each scene frame, providing more control but requiring intensive labor.

  • Typically, film requires 24 frames per second, while graphics terminals need 30 to 60 frames per second to maintain fluidity. On average, 3 to 5 in-betweens are generated between key frames for smoother transitions.

Raster Animations

  • Simple real-time animations can be achieved in raster systems through raster operations.

  • Translations are executed by moving pixel blocks, while two-dimensional rotations, although possible, are complicated by the precision of angles.

  • Color-table transformations facilitate object animation along two-dimensional paths.

Animation Languages

  • Sequence control can be achieved through general-purpose programming languages (such as C, Pascal) or specialized animation languages.

  • Animation functions include:

    • Graphics editing

    • Key-frame generation

    • Action specification (layout of motion paths)

  • Key-frame Systems: These are designed specifically to generate in-betweens from defined key frames, streamlining the animation process.

Motion Specification and Types

  • Motions can be specified in two primary ways:

    • Direct Motion Specification: Involves explicitly defining motion parameters.

    • Abstract (Goal-Directed) Systems: Specify general actions like "walk" or "pick up an object," allowing for more flexibility in animation creation.

Kinematics and Dynamics

  • Kinematic Description: Specifies motion through parameters without reference to forces; often uses spline curves to define paths.

  • Dynamic Description: Requires consideration of forces to determine the resulting velocities and accelerations; essential for simulating complex systems with physical interactions.