Game Development Reference
In-Depth Information
the Stage; you can think of it as followingtheinvisibleline
created from your eyes to the screen.
Position
On the z -axis, the value of 0 is at Stage level. Negative values for the
z property of a DisplayObject would make the object appear larger
and
to the viewer. Positive values for z will increasingly shrink
the object, making it
closer
Flash developers who have per-
formed tricks with the x and y scales of objects in the past to achieve
the feeling of depth and 3D space will no doubt breathe a sigh of relief
at the ease with which this effect can now be achieved with only a line
or two of code. It should be noted that the z position of an object only
tells Flash how to properly render the object in perspective; it does not
affect the display list order. In other words, if you had two objects in a
scene (let
further away.
ssayonewitha z position of 30, whereas the other had a
z position of 10), but the one with the higher z position was added to
the Stage later, it would still appear to be on the top in the display list.
'
Rotation
In addition to 3D positioning, you can also rotate DisplayObjects
around any of the three axes. Figures 11.10
11.12 illustrate how a
DisplayObject is rendered when its rotationX , rotationY ,and rota-
tionZ properties are each set to 45, respectively. You
-
ll notice that
the effect of rotationZ is not unlike the traditional rotation property
from previous versions of Flash.
'
Perspective Projection
At this point it
s important to understand how the 3D transformations
are computed and are applied to give the illusion of 3D space in a 2D
environment. Each DisplayObject in Flash has a vanishing point, that
is, the point in 3D space where all parallel lines heading to the point
appear to converge. The use of just one vanishing point is known as
'
TEXT
Figure 11.10 A DisplayObject
rotated 45° on its x-axis.
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