Hierarchical Modelling

What is heirarchical modelling?

A way to organize complex objects using a heirarchy of simpler componenets to allow easier manipulation and rendering

How are complex objects built in a heirarchy?

By combining simple shapes/ componenets where each part can be transformed independently

Why must transformations sometimes be stopped from interacting?

To prevent unintended effects, like rotating a blade also rotating the tower of a windmill

How are inverse transformations performed?

They cancel out previous transformations when backtracking the scene graph

What is a transformation stack?

A stack structure used to track and restore transformation states during rendering

Stack operations

1. Push

2. Apply Transformation

3. Pop

Push

Saves the current state

Apply Transformation

Applies the new transformstion to the current transformation matrix

Pop

Restores the previous transformation state

What is subroutine in computer graphics?

A reusable function that performs a specific task, like drawing a shape.

How can subroutines from a heirarchy?

By combining smaller routines into components, then a full scene

How does save() and restore() work in canvas?

1. save(): Pushes current canvas state onto the stack

2. restore(): Pops and re-applies the last saved state

What are common canvas transformations?

1. translate(x,y): moves the coordinte system

2. rotate(angle): Rotates the coordinate system around the origin

3. scale(x,y):Scales the coordinate system

4. skew(): skews the coordinate system

What is a screen graph?

A heirarchical data structure for managing objects and their transformations in a scene

How is a scene rendered from a scene graph?

By traversing it and applying cumulative transformations

What are the main node types in a scene graph?

1. SceneGraphNode: Abstract base class for all nodes

2. CompoundObject: Group of multiple child nodes

3. TransformedObject:Applies transformation to a single node

What does CompoundObject do?

Represent an object made of multiple sub-objects added via .add()

What does TransformedObject do?

Wraps a node and applies transformations using .setScale(), .setRotate(), .setTranslate()

What order are tranformations applied in TransformedObject?

Scale→Rotate→Translate

Why don’t these transformations affect other objects?

Beacuse transformations are local to each branch- other branches like cart or windmill remail unaffected

What is animation in graphics?

Creating motion by displaying a sequence of frames over time

What is sprite animation?

Using a sequence of 2D images to simulate movement

What is stop motion?

Capturing physical objects frame-by-frame to simulate motion

What is parallax scrolling?

Moving background layers at different speeds to create depth

What is keyframe interpolation?

Defining key poses and using interpolation to generate smooth transitions

What is motion capture?

Recording real-life actors movements with sensors and applying them to digital models

What is inverse kinematics(IK)?

A method to calculate joint angles so a limb reaches a specific target position

What is procedural animation?

Movement generated by algorithms in real-time instead of pre-defined

Examples of procedural animation?

1. Physics-Based Animation

2. Procedural Walk Cycles

3. Crowd Simulation

4. Dtnamic Environments