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Homework 8 Problems

1. In cinematography, what does the term "crane shot" mean? Give an example.
For a crane shot, a camera is mounted on a crane in order to give the camera the ability to move up, down, and around with more ease. Used in car chases, shot-from-above scenes, and fluid zoom ins and outs. One movie example is To Live And Die in L.A.

2. What is "image synthesis"? Why do we care?
Image synthesis is the process of creating images of synthetic objects or environments. Examples are a camera in the real world, versus a camera in a virtual environment. Creating images from virtual worlds is the basis of all we are setting out to do and create.

3. What is the "line of action"? How does it relate to the "triangle" principle of camera placement?
Following the line of action is the most basic rule of camera placement. It organizes camera angles to preserve consistent screen direction and space and it is used for organizing the shooting plan. The triangle principle of camera placement is a way to describe camera positions on one side of the line. The system proposes that all the basic shots possible for any subject can be taken from three points within the 180 degree working space. Connecting the three points, we have a triangle of variable shape and size depending on the placement of the cameras. Any shot can be joined to any other shot in the triangle system of setups. It is used extensively for live television. There are five basic camera setups that can be obtained within the triangle: Angular singles (medium shots or close-ups), master two-shots, over-the-shoulder shots, point-of-view singles (medium shots or close-ups) and profile shots.

4. What is "parallel editing?" Give an example.
Parallel editing is the task of relating two or more elements. This can include story lines, characters, different events, or a larger number of story lines, characters and events. Types of parallel editing could be (1) The lines of interaction are close together, in the same space. or (2) The lines of interaction are far apart, in different places, and only a common motivation provides the link. One example can be taken from The Lord of the Rings Movie Trilogy. From beginning to end, all of the characters are headed to the same outcome, but along the way they get separated. We get to see clips of each of the different characters as they make their way through the land corresponding to the time that is passing.

5. How is time "compressed" in a film? Give an example.
Time is compressed in a film in various ways. Most importantly, only use what is necessary and builds on to the plot. (We don’t need to see film of every person sleeping in a movie that takes place over the course of two days.) One example is the movie Swiss Family Robinson. The action in the movie takes place over manly months yet the movie is only a couple of hours long.

6. What is a "visible surface algorithm?" Why do we care?
A visible surface algorithm determines what the computer camera ‘sees’ as it renders an image. They are based on sorting in orthogonal space. Computation time depends on image complexity and sorting efficiency. We care because we don’t want the computer to show and render parts of the objects that would not be visible if this was a real world situation.

7. What is a "particle system?" Give an example of when/how a particle system might be used.
A particle system is a system made up of many points, rather than a solid. These points can later be substituted with objects or shapes. For example, fire, clouds or a waterfall.

8. How does the "z-buffer" visible surface algorithm work? What kind of sorting, if any, does it use?
A Z-buffer has two components, a color buffer and a depth (distance from camera) buffer. For an image, it takes and records a color value and depth value at each image pixel, then for each pixel of each surface, it compares depth value and if it is closer than the last recorded value it updates it. There is no explicit sorting.

9. What is the "camera" coordinate system? How does it relate to the "world" coordinate system?
When a scene/object is created in the virtual world, it has its own coordinate system, the “world” coordinate system. When a camera is inserted into this world, it brings in its own “camera” coordinate system where the origin is at the camera and positive z-axis is directed out and away from the center of the camera (depth). All of the object coordinates in the world system must be transformed into the camera system.

10. How does a "ray casting" visible surface algorithm work? What kind of sorting, if any, does it use?
The camera, casts a 'ray' through each image pixel, computes the intersection of this ray with objects in the environment, and finds the intersection closest to camera, and keeps that value. There is no sorting used.