Problem

Ray tracing is too slow. We need to accelerate it!
To make ray tracing faster, we need to solve this problem:

Given a scene defined by a set of $N$ primitives and a ray $\mathbf{r}(t)$, find the closest point $\mathbf{p}$ of intersection of $\mathbf{r}(t)$ with the scene.

Bounding Volume

Idea: Precompute conservative but smallest bounding volume that includes all primitives, then early reject if ray does not hit the box.
Problem: In the worst case, we still need to examine all primitives.

Memory Address Space

User process uses virtual address space, while hardware such as memory uses physical address space.

Device has its own MMU (memory management unit) for virtual to physical address translation.

Virtual address space

MAC address

IP address is used for layer 3, MAC address is used for layer 2!

MAC (or LAN or physical or Ethernet) address is used locally to get frame from one interface to another physically-connected interface.
48-bit MAC address is burned in NIC ROM, but it is software settable nowdays.
e.g. 1A-2F-BB-76-09-AD

Q. How do I get a unique MAC address?
A. There are few network card manufacturers, and each network card manufacturers have unique prefix of MAC address.

MAC address is portable; We can move interface from one LAN to another.
c.f. IP address is not portable! It depends on IP subnet to which node is attached.

Design Heuristics

Goal: Evaluate the evolving design when no users are present.
Why? Using users is the best, but it's not always possible.

• Cognitive Walkthroughs: Path through interface with pre-determined tasks and actions
• Action Analysis: Predict the time for an exper to perform a task
• Heuristic Analysis: Interface oriented, Path through interface (without pre-determined tasks)

Cognitive Walkthrough

Cognitive walkthrough is a formalized way of imagining people's thoughts and actions when they use an interface for the first time.

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