Global Illumination Models

A surface point can receive light from various sources such as light sources and other objects.

• Ray tracing
• Radiosity
• Photon mapping

Recall) Local illumination model: A surface point receives light directly from light sources, no shadows, reflection, transmission.

Ray Tracing

Link layer

• Nodes: Hosts and routers
• Links: Communication channels that connect adjacent nodes along communication path
• Frame: Layer-2 packet that encapsulates datagram

Link layer has responsibility of transferring datagram from one node to physically adjacent node over a link.
Link layer is implemented in each-and-every host, typically in network interface card (NIC) or on a chip.

Context

• Datagram is tranferred by different link protocols over different links. (e.g. Wi-Fi, Ethernet)
• Each link protocol provides different services. (e.g. reliable/unreliable)

Visualization

• Scientific Visualization: Render actual objects
• Information Visualization: Visualize abstract data, also called InfoVis

Benefits of visualization

• External representation acts as an artificial memory that best supports our natural means of perception.
• Problem solving can proceed through a smooth traversal of the diagram.
• Visualizations can reveal structures, while summarization such as mean, variance lose information.

InfoVis Reference Model

Graphic Design

Graphic Design is a fundamental aspect of interface design. It helps users to:

• Follow the expected sequence of interactions
• Understand the organization of data, functions, and tasks
• Build a consistent mental model for efficient use
• Benefit from visual consistency to become more proficient over time
• Brand recognition: Graphic design can provide a distinctive look and feel

Components of the Visual language

• Layout: How the content is structured on the display
• Typography: Typefaces & typesetting
• Imagery: Visual identity, icons
• Sequencing: How interactions unfold

Physical properties of color

• Lights: Things that emit energy to surroundings
• Material: Things that absorb or reflect a portion of incident energy

Light

Types of energy being transferred determines the color of light source.
Visible spectrum: 400nm ~ 700nm

White is defined as a color of the sunlight.
It is actually a mixture of all visible frequencies.

Conceptual models and mental models

Conceptual frameworks help us explain and predict user behavior based on theories of cognition.
Conceptual frameworks help us:

• Understand how users approach a task
• Predict where confusion or failure may occur
• Improve interface design by addressing these breakdowns.

To design effective interfaces, we must align three models:

• Design Model (Conceptual model): The system concept as intended by the designer
• User's Model (Mental model): The user's mental understanding of the system
• System Image: What the system presents to the user through interface and behavior

Network-layer functions

• Forwarding: Move packets from router's input to appropriate router output in data plane.
• Routing: Determine route taken by packets from source to destination in control plane.

Per-router control is a traditional way to implement control plane.
Logically centralized control (SDN) is now used.

Routing algorithm

Goal: Determine good paths (e.g. least cost, fastest, least congested) from sending hosts to receiving host, through network of routers.

GOMS

Model Human Processor (HIP) is good for modeling short, isolated tasks, but it doesn't scale to complex, routine tasks.
e.g. matching a symbol to memory, determining the fastest speed to type on two different keyboards

CNM-GOMS (Card, Newell, and Moran) is a higher-level model that models skilled behavior using Goals, Operators, Methods, and Selection rules.
It predicts the performance time of experienced workers to perform a task with an interface design.
Other model like CPM-GOMS (Critial-Path Method), NGOMSL (Natrual GOMS Language) address learning and/or parallel behvaior.

• Goals: Desired outcomes or tasks
• Operators: Elementary perceptual, motor or cognitive actions
• Methods: Sequences of sub-goals and operators that can accomplish a goal
• Selection rules: Choose between alternative methods available for a given goal

In programmers view, goal is a funtion name, method is a body of a function, selection rules is a program.

Spatial Variation

All materials seen so far are the same everywhere.
i.e. BRDF was independent of location on surface.

We will allow BRDF to vary over a surface!

c.f. Why don't we divide the surface into lots of triangles with same BRDF?
This will make the mesh too complex.
We want to distinguish geometric complexity and material complexity.

Texture Mapping

Reducing model size

Pruning

In fact, pruning also comes from the biological system!
Number of synapses increases before 2 years old, but decreases after 2 years old.
Probably to reduce resource (a.k.a. energy) usage?

In NN, we prune small output neurons and small weight connections.
Then we train the remaining weights, and we repeat this process.

• Model size is reduced
• Faster download
• Less multiplication, a.k.a. less energy consumption!
• Weights tend to diverge