CODEWITHSUNDEEP
actionscript-3
user2130844
user2130844

Reputation: 155

How to make my character move relative to the mouse position with actionscript 3?

ok so i have a character called character_mc and i want it to move towards the mouse when you press the forward arrow and strafe relative to right angles of that.

i am quite new to actionscript so could you please include and example of your code in my original code

Here is my current code:

import flash.events.MouseEvent;
//Event Listners
stage.addChild(crosshair_mc);
crosshair_mc.mouseEnabled = false;
crosshair_mc.addEventListener(Event.ENTER_FRAME, fl_CustomMouseCursor);

function fl_CustomMouseCursor(event:Event)
{
    crosshair_mc.x = stage.mouseX;
    crosshair_mc.y = stage.mouseY;
}
Mouse.hide();

stage.addEventListener(MouseEvent.MOUSE_MOVE,facecursor);
stage.addEventListener(KeyboardEvent.KEY_DOWN, fl_KeyboardDownHandler);
//Functions
function facecursor(event):void
{
    character_mc.rotation = (180 * Math.atan2(mouseY - character_mc.y,mouseX - character_mc.x))/Math.PI + 90;

}


function fl_KeyboardDownHandler(event:KeyboardEvent):void
{
    trace("Key Code Pressed: " + event.keyCode);
    if (event.keyCode == 38)
    {
        character_mc.y = character_mc.y - 5;
    }
    if (event.keyCode == 40)
    {
        character_mc.y = character_mc.y + 5;
    }
        if (event.keyCode == 39)
    {
        character_mc.x = character_mc.x + 5;
    }
        if (event.keyCode == 37)
    {
        character_mc.x = character_mc.x - 5;
    }

}

Upvotes: 0

Views: 1620

Answers (2)

Simon McArdle
Simon McArdle

Reputation: 893

To move your character_mc towards the mouse point you only need the direction vector between the two:

var dir:Point = new Point(mouseX - character_mc.x, mouseY - character_mc.y); 
dir.Normalize();

// The following should be called when the 'up' or 'forward' arrow is pressed
// to move the character closer to mouse point
character_mc.x += dir.x; // dir can be multiplied by a 'speed' variable
character_mc.y += dir.y;

Strafing left and right around the point is a little more tricky:

// Where radius is the distance between the character and the mouse
character_mc.x = mouseX + radius * Math.cos(rad);
character_mc.y = mouseY + radius * Math.sin(rad);

You should find this tutorial useful as it does everything you describe and more: http://active.tutsplus.com/tutorials/actionscript/circular-motion-in-as3-make-one-moving-object-orbit-another/

Upvotes: 0

mitim
mitim

Reputation: 3201

I can tell you the basic concept of how you could do this, but you'll have to apply it to your own code. To involves converting your movement code to use a vector, then modifying the vector to get a direction facing the mouse (or at right angles to that direction) and a little bit of math.

Right now you have the character moving straight along the x and y axis only in each key press case. Left/Right only move along the X and Up/Down only move along the Y.

To move towards the mouse will require the character to move both along the X and Y when the Up/Down/Left/Right keys are pressed. Clearly you can see if you move both the character's x/y positions by the same amount, say 5, then it'll move exactly at 45 degrees (though it'll actually move a step of 7.07 pixels, hopefully you can see why). You can represent this as a vector: (5,5). You can use a Point object to represent this vector:

var movementVector:Point = new Point(5, 5);
trace(movementVector.x); // gives 5
trace(movementVector.y); // also gives 5

With that in mind, you can also use a vector to represent movement straight up and down on the y axis:

// set the x to 0 and y to 5
movementVector.x = 0; // 0 would mean not to move the character along the x
movementVector.y = 5; // using -5 would move the character up

And to move along the x axis only:

movementVector.x = 5; // using -5 would move the character right
movementVector.y = 0; // 0 would mean not to move the character along the y

To do the actual movement of the character would be the same as you are doing now, except you use the vector's values:

character_mc.x = character_mc.x + movementVector.x;
character_mc.y = character_mc.y + movementVector.y;

Now to figure out the proper vector to move on a diagonal from the character's position to the mouse position is pretty simple. The x value of the vector is the x distance from the character to the mouse, and the y value of the vector is the y distance from the character to the mouse.

Let's say the character is ay 125, 100 and the mouse at 225, 150. This means the distance between the character and mouse is 100, 50 x and y. Thus you'd end up with a vector:

movementVector.x = 100;
movementVector.y = 50;

If you were to apply this vector as it is to the character's position as it is, it would arrive at the mouse instantly (and then go beyond it) as the character is moving 100 pixels along the x and 50 pixels along the y right away. The step size would be 111.8 pixels long -too big. You would need to scale it down to the character's speed. You can do this by calling the normalise() method on the Point class to scale down the vector:

trace(movementVector.x); // gives 100
trace(movementVector.y); // gives 50

// assuming '5' is the max speed of the character
movementVector.normalise(5);

trace(movementVector.x); // gives 4.47213595499958
trace(movementVector.y); // gives 2.23606797749979

This would result in a 'step' size of 5 now. Applying this would make your character move 5 pixels towards a point 100 pixels to the right and 50 pixels down from where it started.

To transform a vector exactly 90 degrees, a quick and simple way is to swap the x and y values around.

If you are curious on what normalise() method mathematically does, is that it takes the x and y values of the vector (or point) and divides it by the length to get a unit vector (or a vector with a step size of 1), then times the input you give it to scale it to the desired length.

Upvotes: 1

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