19 - Animation

Question 1

Traditional Cel-Based Animation

Answer 1

all frames are drawings composed by multiple transparent layers (cel), and differ (slightly) from one frame to the next to create the illusion of motion

Question 2

Stop Motion

Answer 2

the animation is created by moving characters and objects by small increments to create the illusion of movement.

Question 3

Computer Animation

Answer 3

model how objects and their surfaces actually change – i.e. it requires us to create articulated objects.

The animation of a model is controlled by a set of animation variables (also knows as Avars).

Question 4

Physics-Based Animation

Answer 4

physical objects are assigned properties (e.g. mass, forces etc.). Motion is then calculated by simulating physics (e.g. dynamics or collision)

Question 5

Particle Systems and Flocking Behaviour

Answer 5

allow the modelling of complex motions (as the simulation of a large number of simple particles).

Particles are spawned, transformed and killed at each update according to physics rules.

Flocking behaviour also implements particle awareness of neighbours in their dynamics.

used to create scenes of fire and fog

Question 6

Key Frames

Answer 6

In cases where it is too expensive to create all intermediate images of an animation, key frames may be used.

Using key frames, motion is defined by specifying the scene only at specific instances (i.e. the key frames), and in-between frames are generated by interpolation.

not to have big gaps in-between key frames as this would result in distortions

Question 7

Morphing

Answer 7

Morphing stores a deformed version of the mesh, and uses interpolation to calculate intermediate meshes.

Morphing essentially involves modifying vertices on a mesh

Question 8

Skeletal Animation types

Answer 8

Rigging
Inverse Kinematics

Question 9

Rigging

Answer 9

to control mesh animation, a hierarchical skeletal structure (or rig) is created, consisting of articulated joints, bones and mesh vertices.

This technique provides a simpler (and more intuitive) interface for mesh animation

Each bone in the skeleton is connected to a parent bone, and maintains a transformation in 3D that is a combination of scaling, translation and rotation.

since the movement moves backwards, transformations at the end may affect transformations towards the start

Question 10

Inverse kinematics

Answer 10

calculates the skeleton parameters to bring a given joint to a specified pose.

Question 11

Skinning

Answer 11

Rigging alone results in some weird images since it only models rigid movement, and not soft tissue movement .

It is therefore used alongside skinning, which models soft tissue movement.

Skinning is the process of defining how a model’s surface deforms according to changes in the skeletal pose.

Question 12

Motion Capture

Answer 12

Motion capture is the process of recording the movement of human actors for animating a computer model, and allows fast capture of realistic motion.

Reflective markers are placed at joint locations on the subject, and multiple synchronised cameras view the subject from different angles.

Limitation, not always possible or practical to place all markers or follow them.

Question 13

Motion Graphs

Answer 13

Motion graphs represent possible transitions between recorded motions – they essentially take a frame from each of the recorded motions, which are similar, and aim to interpolate between these to give a smooth transition.