Computer-Based Animation

● To animate something – to bring it to life ● Animation covers all changes that have visual effects – Positon (motion dynamic) – Changes in object properties (color, shape, structure, transparency, texture – Changes in lighting, camera position ● Computer-based animations are produced, edited, and generated with the help of computer using graphical tools to create visual effects

Computer-Based Animation ● animations are composed of individual graphic images called frames ● frames are displayed at a rate fast enough to be perceived as continuous motion ● animation software help to automate the creation of animated graphics

Basic Concepts ● Input Process ● Composition Stage ● Inbetween Process ● Changing Colors

1. Input Process ● Drawings must be digitized to create key frames, where the entities being animated are at extreme or characteristic positions. ● Input Process: optical scanner, sketching using data tablet, any drawing tools etc.

2. Composition Stage ● Individual frames in a completed animation are generated by using image composition techniques to combine foreground and background elements ● image-composition technique

3. In-betweening In-betweening automates the creation of animated sequences key frames are defined for starting and stopping positions the software calculates the incremental frames

Inbetween processing is done using interpolation methods. The system obtains only the beginning and end positions. Linear interpolation, called Learping - simplest method. Calculate the intermediate positions between start and end frame. ● Splines method often used to smooth out the interpolation between key frame ● Inbetween processing also includes interpolation of the form of the objects in the intermediate frame 3. In-betweening

Linear Interpolation of the motion of the ball: (a) Key Frames. (b) additional intermediate frames  Learping method will calculate the intermediate frame using 3 key frames as shown in (a)  Learping output shown in (b). Unrealistic output especially when the ball reaches the top point

4. Changing Colour ● Computer-based animation uses the Color Look-up Table (CLUT) of the graphics memory and the double buffering methods, whereby two parts of a frame are stored in different areas of graphic memory.

Methods of Controlling Animation 1. Explicitly Declared (Full Explicit) Control 2. Procedural Control 3. Constraint-based Systems 4. Tracking Live Action 5. Kinematics and Dynamics

1. Explicitly Declared Control ● Simplest type of animation control ● Animator provides a description of all events that occur in an animation ● Specify simple transformations – scalings, translations and rotations. ● Interpolation can be specified either explicitly or, in an interactive system through direct manipulation with a mouse, joystick, data glove, or other input device.

2. Procedural Control ● Based on communication among different objects whereby each object obtains knowledge about static or dynamic properties of other objects ● Physically-based system: the position of an object can influence the movement of other objects (for example, ensuring the balls cannot move through walls) ● Actor-based systems: individual actors can pass their positions along to others in order to influence their behaviour

3. Constraint-based Systems ● Although some objects in the real world move along in straight lines, this is not always the case. Many objects’ movements determined by other objects with which they come in contact. ● This include object to stop, changing direction etc.

4. Tracking Live Action ● By examining the motions of objects in the real world, one can animate the same movement by creating corresponding sequences of objects ● Traditional animation uses rotoscoping ● A film is made in which people or animals act out the parts of the performers in the animation. Afterwards, animators process the film, enhancing the background and replacing the human actors with the animated equivalents they have created ● Another technique is to attach indicators to key points on the body of a human actor. The coordinates of the corresponding key points in an animated model can be calculated by observing the position of these indicators. ● Example: data glove which measures the position an orientation of the wearer’s hand, as well as the flexion and hypertension of each finger point

5. Kinematics and Dynamics ● Kinematics refers to the position and velocity of points. ● Example” “the cube is at origin at t=0. Thereafter it moves with constant acceleration in the direction (1 meter, 1 meter, 5 meters).” ● Dynamics takes account the physical laws that govern kinematics (Newtonian laws for the movement of large bodies, or the Euler-Lagrange equations for fluids) ● Example: ““the time=0, the cube is at position (0 meter, 100 meter, 0 meter). The cube has a mass of 100 grams, the force of gravity acts on the cube”. The natural reaction in a dynamic simulation is that the cube would fall.

Animation in Multimedia ● Give emphasis on something (navigational button that animates when user touch on it) ● Give continuity among topics or chapters ● Shows or explains a process through simulation