Game Development Reference

In-Depth Information

AS3.0 has a built-in method called I]pd*]p]j. that will give you the correct angle of rotation between

two objects. One little technical detail you need to deal with, though, is that I]pj*]p]j. returns the

value of the angle in
radians
, and Movie Clip (and Sprite) objects in AS3.0 don't use radians for their

rotation values; they use degrees. So once you've got the value in radians, you need to apply a very

simple calculation to convert it into degrees. When you have that value, you can rotate the object.

Let me show you just how easy this all is. Figure 9-19 is a grid showing the positions of two objects on

the stage.

X

0

1

2

3

4

5

6

1

2

Y

3

4

5

Figure 9-19.
Find the angle of rotation between two objects.

Here's how to find out the angle of rotation, from the point of view of the frog:

1.
Find the positions of the objects:

_]p*t91

_]p*u9-

bnkc*t9-

bnkc*u90

2.
Subtract the t and u positions of the target object, from the t and u position of the object that

will be doing the rotating:

bnkc*t)_]p*t9)0

bnkc*u)_]p*u9/

3.
Plug these numbers into the I]pd*]p]j. function. Very importantly, the u value has to come

first:

I]pd*]p]j.$/()0%