3D (three-dimensional) is a way of representing objects as solid forms by adding depth to height and width.
Flat representation (2D)
Computer-drawn solid (3DCG)
Information held
Vertical and horizontal positions
Shape with height, width and depth
Viewing angle
Fixed by how it was drawn
Viewpoint can move around it
How it is drawn
Flat image shown as is
Computed from viewpoint and lighting
In computer-drawn 3D (3DCG), an object's shape is stored as shape data that includes depth, and its appearance is calculated from the viewing position and light direction before it is drawn on screen. Because the shape itself is stored, the viewpoint can change and the viewer can move freely through the space. This property is what the simulators and games covered next are built on.
AnalogyA house drawn on paper has no back to look at, but a clay model of a house can be turned in your hand to see its back and the top of its roof.
How to rememberThe D stands for Dimension, so 3D means 'three dimensions'.
Exam points
Mix-upWhether an image is 3DCG does not depend on whether the screen is flat. An image calculated and drawn from shape data that includes depth is 3DCG even when it appears on a flat screen.
A simulator (シミュレーター) is a system that reproduces real equipment or events on a computer, used to train operators and to verify outcomes.
Set the conditions
Reproduce them
Check actions and results
Change conditions and repeat
Unlike testing on the real thing, you can change conditions and start over as often as you like.
4 / 4
Simulators are used when the real thing would be too dangerous or costly, or when rare situations are hard to set up. By recreating a cockpit and its surroundings in 3D and changing the state as the user operates it, they let people repeat a near-real experience safely. Typical uses include flight and driving training and rehearsing how to respond when a machine breaks down.
AnalogyIt is the same idea as running full rehearsals again and again in a hall set up with the same scenery before opening night.
How to rememberThe word comes from 'simulate', meaning to imitate.
Exam points
Mix-upA simulator (シミュレーター) reproduces real equipment or events, and 3D imagery is only one way of doing that. What defines it is not how it displays things but its use as a stand-in for trying things in the real world.
A game (ゲーム) is a familiar use of 3D and CG for entertainment, redrawing the screen on the spot as the user plays.
A 3D game stores characters and backgrounds as solid shape data, and each time it receives input it calculates how they look and displays them (real-time rendering, リアルタイム描画). Because the player's input decides the next frame, the same scene looks different for each person who plays it.
AnalogyUnlike a picture-card show that always runs in the same order, it is like a storyteller who draws the next picture on the spot when a listener says 'go right'.
Exam points
Mix-upA game (ゲーム) and a simulator (シミュレーター) both change the screen in response to input, so the mechanism alone does not separate them. The dividing line is purpose: entertainment means a game, while training or verification means a simulator.
4K is an ultra-high-definition video standard with about 4,000 pixels across (typically 3,840 × 2,160).
A pixel is one of the colored dots that make up a screen, and on screens of the same size, more pixels mean a finer image. The typical 4K resolution doubles both the width and the height of Full HD (フルハイビジョン, 1,920 × 1,080), so the total pixel count is about 4 times larger.
AnalogyIt is like covering the same floor with slightly smaller tiles instead of large ones, which makes the curves in the pattern look smoother.
How to rememberK is kilo (thousand). 4K = about 4 thousand dots in a row across.
Exam points
Mix-upThe 4 in 4K comes from the horizontal pixel count (about 4,000). It has a different origin from the total pixel ratio against Full HD (フルハイビジョン), which also happens to be about 4 times.
8K is an ultra-high-definition video standard with about 8,000 pixels across (typically 7,680 × 4,320), able to show finer images than 4K.
Because the pixels are so fine, the dots are hard to notice even close up to a large screen. In return, each frame carries more data, so cameras, transmission links and displays all need higher performance.
AnalogyIt is like re-tiling the 4K floor with tiles half as long and half as wide. The same floor can then hold an even finer pattern.
Exam points
Mix-upThe numbers in 8K and 4K differ by a factor of 2, but their total pixel counts differ by about 4 times. The name gives only the horizontal count, and the vertical count grows by the same ratio, so the two must be multiplied.
4K vs. 8K
Aspect
4K
8K
Key differenceHorizontal pixels (typical)
3,840 (about 4,000)
7,680 (about 8,000)
Vertical pixels (typical)
2,160
4,320
Total pixels vs. Full HD
About 4 times
About 16 times
Key points
Computer-drawn 3D (3DCG) works out how objects look from shape data that includes depth, based on the viewing position and light direction, and draws them on screen.
A simulator recreates reality so that dangerous or costly things can be tried safely, as many times as needed.
A game uses 3D and CG for entertainment and redraws the screen on the spot with every input.
The K in 4K and 8K means thousand, and the number in each name is the rough horizontal pixel count.