3D throw ball
[ July 22, 2004 ] by Eric Lin
Intermediate 3D scripting for Flash part 5/5:
Learn how to create an interactive 3D bouncing ball

If you have experience in making 3d flash movie, the scripts are nearly self -evident. No secrets here. You can close this page now. It is a good practice for beginner to create a 3d movie like this. The first step is learning the scripting about throw a ball in 2 D plane. Usually we do it by a parabolar equation. It is scripted as "acceleration".

onClipEvent (load) {
    xSpeed = 5;
    ySpeed = -40;
    gravity = 1.5;
    x = _x;
    y = _y;
onClipEvent (enterFrame) {
    ySpeed += gravity;
    x += xSpeed;
    y += ySpeed;
    _x = x;
    _y = y;

This is enough for throw a ball. Then we will add bounce when the ball hit the ground. I will not talk about this now.
Notice my coding style. I manipulate x, y instead of _x, _y. Only at the last line, I make _x=x;_y=y; to show it on the screen.

This way, the codes are the same of 3D movie. Only the last lines _x=x;_y=y; will change. The second step is borrow a 3d equations, and make your Xspeed into Zspeed, because we want throw to the Z direction.

Now apply the 3d equation to get _x, _y, _z according to the x,y,z;
The simplest 3d equation is in the form of scale=M/(N+z); or scale=zoom*(100/100+z);

zoomZ = 100;
shiftX = 0;
shiftY =0;
PZ = {x:50, y:250};

function f3dscale (z) {
    var scale = zoomZ*z0/(z0+z);
    return scale;
function f3dPoint (x, y, z) {
    var x3d = (x+shiftX)*f3dscale(z)/100+PZ.x;
    var y3d = (y+shiftY)*f3dscale(z)/100+PZ.y;
    var pt = {x:x3d, y:y3d};
    return pt;

 So, for a ball with x,y,z


Download the source code of this prototype

Name: Eric Lin
Location: Taiwan
Age: 46
Flash experience: Since Flash 5, about 4 years
Job: neurosurgeon (a doctor who operates people's brain)
Website: http://ericlin2.tripod.com/
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