Re: FLASH: starfield using arctangent available!

[Kurt Dommermuth]

>Without looking at the FLA (not at a computer with Flash :( can I ask what

>you are using the arctan() for?

>Perspective effects are a simple z divide. Or am I missing something?

>

>Barry

>

gerbiltheburrow [dot] co [dot] uk

Hi Barry,


I don't know what z divide means.  If you could explain I would appreciate 

very much.  Frankly, I know very little math and am trying to learn as much 

as I can.


I'd be glad to know there was a simpler solution than arctan to solve my 

problem.  I wrote to the list last week asking about this and no one 

offered a better way!  As convoluted as this became, I know there must be 

and all you math jocks were just holdin out on me dammit.


Anyway, I started to go into the long explanation of what I was doing and 

thought maybe it would be clearer to just include the code....


Set Variable: "count" = count + 1

Set Variable: "j" = 0

Loop While (j < 10)

Set Variable: "p" = count &j

Duplicate Movie Clip ("/star", "star" &p, p)

Set Variable: "locationX" = Random (100) + 350

Set Variable: "locationY" = Random (100) + 150

Set Variable: "scale" = Random (30) + 30

Set Property ("/star" &p, X Position) = locationX

Set Property ("/star" &p, Y Position) = locationY

Set Property ("/star" &p, X Scale) = scale

Set Property ("/star" &p, Y Scale) = scale

Comment: Determine Center of Screen

Set Variable: "x" = (locationY - 200) / (locationX - 400)

Comment: **************************

Comment: Begin Arctan Function

If (x > -1.0 and x < 1.0)

Set Variable: "arctan" = x-(x*x*x/3)+(x*x*x*x*x/5)-(x*x*x*x*x*x*x/7)

Set Variable: "output" = (arctan * 180) / 3.1416

Else If (x >= 1)

Set Variable: "arctan" = (3.1416 / 2) - (1 / x) + (1 / ( 3 * (x*x*x))) - (1 

/ (5 * (x*x*x*x*x))) + (1 / (7 * (x*x*x*x*x*x*x)))

Set Variable: "output" = (arctan * 180) / 3.1416

Else If (x <= -1)

Set Variable: "arctan" = - (3.1416 / 2) - (1 / x) + (1 / ( 3 * (x*x*x))) - 

(1 / (5 * (x*x*x*x*x))) + (1 / (7 * (x*x*x*x*x*x*x)))

Set Variable: "output" = (arctan * 180) / 3.1416

End If

Comment: End Arctan Function

Comment: *************************

Comment: Output is between -90 and 90 degrees.  The following compensates 

for this.  Anything left of center we add 180 degrees.

If (locationX < 400)

Set Property ("/star" &p, Rotation) = output +180

Else

Set Property ("/star" &p, Rotation) = output

End If

Set Variable: "j" = j + 1

End Loop


Basically just telling a randomly placed MC to find the center of the 

screen and rotate directly away from it.  I tried turning it inwards which 

was cool and also used the mouse coordinates as the center and that was 

pretty cool too.


Again, if you know a better way I would be grateful as I really would love 

to use this in a clients animation I'm currently working on and as it 

stands now it is probably too processor intensive.


Muchos Gracias,

Kurt

http://www.dommermuth-1.com



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