as3 mathmatic help!

[Never_land:(]

I'm trying to make the red ball(ball_mc) stay in that line between a1 & a2
and I want is position to be relative to the mouseX,MouseY in a perpendicular way(90 degrees).
please help!

[realMakc]

here you go.

[Never_land:(]

Can you give me some code example.

[newblack]

public static function getClosestPointOnLineSegment( a:Point, b:Point, point:Point ) : Point
{
    
    //vector pointing from a to b
    //all valid points on the given line segment satisfy a + diff * t for 0 <= t <= 1
    var diff:Point = b.subtract( a );
    //vector pointing from a to point
    var pa:Point = point.subtract( a );
    //project the point onto diff- divide by the squared magnitude of diff to solve for t
    var t:Number = ( diff.x * pa.x + diff.y * pa.y ) / ( diff.x * diff.x + diff.y * diff.y );
    //working with a line segment, ensure t doesn't exceed legal limits
    t = Math.max( Math.min( 1, t ), 0 );
    
    return new Point( a.x + diff.x * t, a.y + diff.y * t );
    
} 

a and b are the 2 endpoints of the line segment, point is the center of your circle. you'll have to import flash.geom.Point.

the link realMakc posted should be sufficient to understand the algorithm.

[Never_land:(]

thanks, sorry, I'm new with the package thing.
I saved your code in ".as" file as linear.as
___________________
1012: The static attribute may be used only on definitions inside a class.

var th_class:linear= new linear()
addChild(th_class)

any help.

[newblack]

if you're just writing the function in Flash, lose public and static (just keep function)

[realMakc]

newblack of course you do realize that by giving code you do not help... /unsub

[Never_land:(]

I learn better in actionscript.

[newblack]

newblack of course you do realize that by giving code you do not help... /unsub

that's pretty insulting considering i tried my best to comment the code such that it explains why and how it works...

[Never_land:(]

It took me some time but I understand it now.
THANKS NEWBLACK!

[Suthers]

you want the ball to change as the mouse's x position changes.

ball_mc.x=mouse.x;

but you want it in-between a1 and a2 which are have pixel locations, that you can find.

a1.x=pixel location#
a1.y=pixel location#

a2.x=pixel location#
a2.y= pixel location#

Your code may have somethig like this.

if(mouse.x<=a2.x){...}
else if(mouse.x>=a1.x){...}
else{}

Also, you may want to look at slope intercep form of a line:

y=mx+b

Google it

[Suthers]

You can work out the bugs of this. I did it quickly:
var p=element ("dot");
var p1=element ("point1");
var p2=element ("point2");

//y=mx+b (equation of a line)

//slope = rise/run



stage.addEventListener(Event.ENTER_FRAME, move)

function move(evt:Event):void
{
var slope:Number = ((p2.y)-(p1.y))/((p2.x)-(p1.x))

p.x=mouseX



p.y = slope * p.x +400
}

the "+400" part should vary