Datasheet

6
Part 1: Getting Started
Creating the illusion of depth (or 3D) using perspective scaling is sometimes referred to as 2.5D.
Another term used to describe perspective projection is 2.5D. The term is usually used with computer
graphics, especially video games, where a computer system uses 2D computer graphics to visually
simulate 3D computer graphics. In Flash, you use the z perspective scale to create a perspective
projection onto the Flash x, y screen.
Deriving the Scaling Equation
You ’ re probably wondering how the scaling equation presented above was derived. As mentioned
earlier, it came from Thales ’ idea of similar triangles. The figure below shows two nested (or similar)
triangles. Small h is the size of an object at the computer screen and large H is the actual size of the object
beyond the screen. And as described earlier fl (or focal length) is the distance from your computer screen
to your eye, and z is the distance on the other side of your screen to your object as shown in Figure 1.3.
Figure 1-2
Computer Screen
h
fl
z
H
Vanishing Point
Figure 1-3
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