Physics in Papervision at Papervision 3D Tutorials

Hi Everyone!

Today I've been experimenting with Verlet physics, and using Papervision to render the results. Here's what I've come up with:

It's a little bit buggy, but pretty good for a quick papervision project!

I had to modify the DisplayObject3D class a bit, It's a tiny modification which just allows you to store an acceleration and "previous position" in any object. I added the variables because it was the easiest and quickest way to store this information.. And my physics formula needs them.

If you want to play with it, you'll have to download my modified DisplayObject3D class by clicking here

Just replace your current file (located in Greatwhite/src/org/papervision3d/objects) with my one. It won't affect the performance or anything on projects which also use this class (I've only added two or three lines).

Here is the code (Uses the base class and modified DisplayObject3D):

PLAIN TEXT

Actionscript:

package {
import flash.display.StageQuality;
import org.papervision3d.core.geom.renderables.Vertex3D;
import org.papervision3d.lights.PointLight3D;
import org.papervision3d.materials.shadematerials.FlatShadeMaterial;
import org.papervision3d.materials.shadematerials.PhongMaterial;
import org.papervision3d.objects.DisplayObject3D;
import org.papervision3d.objects.primitives.Plane;
import org.papervision3d.objects.primitives.Sphere;
public class Main extends PaperBase {
public var light:PointLight3D = new PointLight3D(true);
public var physBox:DisplayObject3D = new DisplayObject3D(); //We'll keep all of the physical objects in here..
public var sidemat:FlatShadeMaterial = new FlatShadeMaterial(light, 0xBBBBBB, 0x000000);
public var floor:Plane = new Plane(sidemat, 1100, 1100, 10, 10);
public function Main() {
stage.quality = StageQuality.LOW; //Set the stage quality to low (for speed)
init();
}
override protected function init3d():void {
//Position the floor
floor.y = -100;
floor.pitch(90);
default_scene.addChild(floor);
//Position the camera
default_camera.y = 300;
default_camera.z = 1500;
default_camera.lookAt(floor);
//Position the light
light.x = 0;
light.y = 300;
light.z = 500;
//Create 10 Spheres, and put them in our Physics Box (Anything you add to physbox will be simulated, only spheres look right)
for (var x:Number = 0; x <10; x++) {
var sph:Sphere = new Sphere(new PhongMaterial(light, 0xBBBBBB, Math.round(Math.random() * 10000), 20), 100, 10, 8);
sph.x = (Math.random() * 40) - 20; // Position it slightly randomly
sph.z = (Math.random() * 40) - 20;
sph.y = (300 * x); // Put it 300 px above the previous one
sph.PreviousPosition = new Vertex3D(sph.x, sph.y, sph.z); // This stops the verlet from going crazy
physBox.addChild(sph); // Add it to the physbox
}
default_scene.addChild(physBox); // Add the physbox to the scene
}
override protected function processFrame():void {
default_camera.moveLeft(20); //This will rotate our camera around the scene,
default_camera.lookAt(floor);//whilst keeping it looking at the middle.
for (var item:String in physBox.children) { // This loop is run for every sphere in our physBox.
var citem:DisplayObject3D = physBox.getChildByName(item); // Get the sphere.
var lastposTmp:Vertex3D = getPos(citem); // Temporarily store it's position.
// This line of code is known as "Verlet". Wikipedia it for more info.
setPos(citem, vertexAdd(getPos(citem), vertexAdd(vertexSubtract(lastposTmp, citem.PreviousPosition), citem.Acceleration)));
citem.PreviousPosition = lastposTmp; // Update the previous position..
citem.Acceleration = new Vertex3D(0, -8.3, 0); // Apply Gravity
constrain(citem); // This code checks if the sphere has collided with the environment.
for (var item2:String in physBox.children) { //Check to see if it's hit any other spheres.
if (item != item2) {
var pitem:DisplayObject3D = physBox.getChildByName(item2);
dohittest(pitem, citem); // Check
}
}
}
}
private function dohittest(o1:DisplayObject3D, o2:DisplayObject3D):void {
if (o1.hitTestObject(o2)) { // IF the two objects have collided, then
var xmag:Number = (o1.x - o2.x)/2.1; // Get the distance
var ymag:Number = (o1.y - o2.y)/2.1;
var zmag:Number = (o1.z - o2.z)/2.1;
// Move the objects away from eachother
setPos(o1, vertexAdd(new Vertex3D(xmag, ymag, zmag), getPos(o1)));
setPos(o2, vertexSubtract(getPos(o2),new Vertex3D(xmag, ymag, zmag)));
}
}
private function constrain(obj:DisplayObject3D):void {
if (obj.x <500 && obj.x> -500 && obj.z <500 && obj.z> -500){ // If the object is over the floor
if (obj.y <0) { // If it's hit the floor
// Move it out of the floor.
if((obj.y - obj.PreviousPosition.y) <-10){
obj.y = (obj.PreviousPosition.y * 1.2);
if (obj.y <0) {
obj.y = 0;
}
}else {
obj.y = 0;
}
}
}
// If the object is way off the screen, put it back at the top.
if (obj.y <-10000) {
obj.y = 300 + (Math.random() * 5000);
obj.x = (Math.random() * 20) - 40;
obj.z = (Math.random() * 20) - 40;
obj.PreviousPosition = new Vertex3D(obj.x, obj.y, obj.z);
}
}
// --- These functions are used to do general addition and stuff ---
private function vertexSubtract(v1:Vertex3D, v2:Vertex3D):Vertex3D {
return new Vertex3D(v1.x - v2.x, v1.y - v2.y, v1.z - v2.z);
}
private function vertexAdd(v1:Vertex3D, v2:Vertex3D):Vertex3D {
return new Vertex3D(v1.x + v2.x, v1.y + v2.y, v1.z + v2.z);
}
private function getPos(object:DisplayObject3D):Vertex3D {
return new Vertex3D(object.x, object.y, object.z);
}
private function setPos(object:DisplayObject3D, point:Vertex3D):void {
object.x = point.x;
object.y = point.y;
object.z = point.z;
}
// --- ---
}
}

I hope it's commented enough

Have fun!

16 Responses to “Physics in Papervision”

Feed for this Entry Trackback Address

1 Joakim
February 22, 2008 at 12:50 pm

If you have the time, could you do some demo using WOW. The engine looks very interesting, but the documentation available is very scarce. I need some besic demos to get the hang of it.

Would be very much appreciated.
2 cslamsg
February 25, 2008 at 3:31 pm

Hi,

Coming across the demo is indeed very interesting. Great !

I am now currently working around quaternion physics. Cheers.
3 Luke
February 26, 2008 at 11:38 am

Hi Joakim,

If I get the time I will, I still haven’t looked into WOW yet though, and thanks for the comment cslamsg, would be cool to see what you come up with :)!

-Luke
4 Manuel
March 18, 2008 at 7:42 pm

Thanks for the great example!
Found something similar using papervision and the wow physics engine here: http://lab.tojio.com/projects/wowpv3dhelloworld/
5 George Profenza
June 12, 2008 at 11:21 am

Hi,

Thanks for the example. I’ve downloaded your modified version of DisplayObject3D and it doesn’t work. Apparently it doesn’t have the clone method and related properties. Any reason why these might be left out ?
6 George Profenza
June 12, 2008 at 11:48 am

Why not just create a DisplayObject3DPhys for example, that extends DisplayObject3D ?
7 Amanita
June 17, 2008 at 10:32 am

What kind of Papervision3D version do you have???
8 Amanita
June 25, 2008 at 8:23 am

Sorry, but GreatWhite doesn`t work. Phong shader materials classes is wrong ((
9 wizim
June 29, 2008 at 12:12 pm

WoW where is your PaperBase Class? give me pleasssssse.
10 wizim
June 29, 2008 at 12:15 pm

oh i see it.Thx
11 Maceo
July 15, 2008 at 2:58 pm

It doesn’t work… there seems a problem with the override function in the vertex3d class. i think something is wrong with your new “DisplayObject3D”!!! can u check this????
12 quentin
August 12, 2008 at 2:44 pm

Hello Luke,
Papervision 2 it’s great i think that it was change interactivity on the web.
But i’m the same error that Maceo, i had to replace DisplayObject3D class but it doesn’t work and make trouble with another project like “Fun with Filters”.
Maybe it’s us can you check the new Displayobject class ? thx
13 Adam
September 11, 2008 at 12:42 am

Thank you soooo much for your brilliant examples. I was able to use your collision detection ideas to solve some frustrating issues I was having.
14 Rocky
October 24, 2008 at 4:50 pm

The solution to the DisplayObject3D is the following:

you insert these 2 lines in the class

public var Acceleration:Vertex3D = new Vertex3D(0, 0, 0);
public var PreviousPosition:Vertex3D = new Vertex3D(0,0,0);

and you import the Vertex3D class to the package.

That’s how I got mine to work.
15 Shajby
January 30, 2009 at 6:51 pm

Hi,

I have tried to demonstrate new physics engine jiglib on my bowling game

http://moth.cz/bowl/bowlec.html
16 BePresents.com
May 7, 2009 at 11:36 pm

This is great!

Do you have any mechanism worked into your code yet to give different objects different weights, for the bounces? And what about immovable objects?

If no, I’ll adapt DisplayObject3d.as to incorporate those.