Datasheet

Part 1: Getting Started

import flash.display.Sprite;//imports sprite class

var zposition:Number = 0;//z position

var myAngle:Number =0;//Angle of ball

var fl:Number = 300; //focal length

var ball:Sprite = new Sprite();//instantiates ball sprite

ball.graphics.beginFill(0xFF0000);//Assign a ball color

ball.graphics.drawCircle(0, 0, 40);//draws your ball at 0,0

ball.graphics.endFill();//ends the fill

addChild(ball);//adds the ball to the stage

addEventListener(Event.ENTER_FRAME, onEnterFrame);//loops equations

function onEnterFrame(event:Event):void{

var scale:Number = fl / (fl + zposition);//scale perspective

myAngle=myAngle+.1;//iterates angle

myB all.x = 300*Math.sin(myAngle)*scale; //ball orbit x

ball.y = 300*Math.cos(myAngle)*scale; //ball orbit y

ball.scaleX = scale;//scales perspective in x

ball.scaleY = scale;//scales perspective in y

zposition = 2000*Math.sin(myAngle/10);} //increments z and changes sign

The code, though it ’ s not Papervision3D, illustrates a number of important concepts that every 3D

engine possesses:

A frame looper/renderer

Perspective (z - coordinate)

Projection onto a viewport

Primitive or basic shape

Addition of a color (or material)

And all of this is done in just 19 lines of code. If only it had stayed this simple. Papervision3D started off

with only 20 classes, now it ’ s in the hundreds and growing. But as they say, no pain no gain.

Vanishing Point (Asymptotic Zero)

As your animation runs, the spiraling red ball approaches its vanishing point (asymptotic zero), which

as mentioned earlier, is the Flash origin located at (0, 0) or upper left position of your screen. This is a

little annoying, but can be easily adjusted by moving your vanishing point. This is done by adding

a vanishing point coordinate value to your ball x and y positions. To center the vanishing point to the

Flash stage you must import the stage class and use

stage.stageWidth/2 (which returns the x center

point) and

stage.stageHeight/2 (which returns the y centerpoint) as shown here:

ball.x = 300*Math.sin(myAngle)*scale+stage.stageWidth/2;

ball.y = 300*Math.cos(myAngle)*scale+stage.stageHeight/2;

The results of this change are shown in Figure 1.6.

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