CS426 Lecture 5: Projective Transformations

Flashcards about Projective Transformations and Computer Graphics.

What is the purpose of a digital micro-mirror device (DMD) in a DLP projector?

To produce color images, typically using three DMDs.

What resolutions are typically used in digital micro-mirror devices?

Typically 2K (2048x1080), but 4K is also available.

What is Digital Cinema used for?

RealD (3D) and IMAX viewing.

What is the typical lumen output of lecture room projectors and what is the lux when projected onto 6m^2?

About 3000 lumens, resulting in about 500 lux.

What was the total lumen output of the 36 Barco FLM HD 20K projectors used for the Buckingham Palace Diamond Jubilee Concert?

720,000 lumens.

What was the approximate lux on the front of Buckingham Palace during the Diamond Jubilee Concert?

300 lux

What is the approximate lux of daylight?

25,000 lux

What is the approximate lux of indoor lighting?

80 lux

What happens to Z information in orthographic projection?

Z information is lost.

Where is orthographic projection commonly used?

Engineering drawings (plan, elevation etc.).

What is a key characteristic of orthographic projection regarding object size and range?

No change in image size of an object as range (Z) changes.

In orthographic projection, how are X, Y, and Z mapped to x, y, and z?

x = X, y = Y, z = 0

What effect does a wide-angle lens have on the field of view and focal length?

Wide field of view, short focal length (d small).

What effect does a telephoto lens have on the field of view and focal length?

Narrow field of view, long focal length (d big).

What is 'd' in perspective projection?

Centre of projection (focal length of lens).

In perspective projection, what points are (X, Y, Z)?

Points on the model after positioning in the world.

In perspective projection, what do x and y represent?

Points on the image plane.

What is the formula for x in perspective projection?

x = (dX) / Z

What is the formula for y in perspective projection?

y = (dY) / Z