Talking about Shrink it game, Actionscript 3, Box2D, Flash and Game development.
Finally the Shrink it prototype is ready.
This post continues Scaling objects with Box2D and Scaling objects with Box2D – part 2, with these features:
1) You can’t modify static objects
2) You can shrink objects with left mouse button, and expand them with left mouse button + SPACE, as in the original game
3) You can shrink/expand any polygon thanks to Ilya‘s suggestion made in this post.
Now in the stage we have four objects: a circle, a square, a triangle and a custom shape. Refer to Understanding custom polygons in Box2D for more information about custom shapes.
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.events.KeyboardEvent;
import Box2D.Dynamics.*;
import Box2D.Collision.*;
import Box2D.Collision.Shapes.*;
import Box2D.Common.Math.*;
public class shrink extends Sprite {
var body:b2Body;
public var m_world:b2World;
public var m_iterations:int=10;
public var m_timeStep:Number=1.0/30.0;
public var mousePVec:b2Vec2 = new b2Vec2();
// variable to store if the player is pressing SPACE
public var space_pressed:Boolean=false;
public function shrink() {
var worldAABB:b2AABB = new b2AABB();
var bodyDef:b2BodyDef = new b2BodyDef();
var polygon:b2PolygonDef = new b2PolygonDef();
var circleDef:b2CircleDef= new b2CircleDef();
worldAABB.lowerBound.Set(-100.0, -100.0);
worldAABB.upperBound.Set(100.0, 100.0);
m_world=new b2World(worldAABB,new b2Vec2(0,10),true);
// debug draw start
var m_sprite:Sprite;
m_sprite = new Sprite();
addChild(m_sprite);
var dbgDraw:b2DebugDraw = new b2DebugDraw();
var dbgSprite:Sprite = new Sprite();
m_sprite.addChild(dbgSprite);
dbgDraw.m_sprite=m_sprite;
dbgDraw.m_drawScale=30;
dbgDraw.m_alpha=1;
dbgDraw.m_fillAlpha=0.5;
dbgDraw.m_lineThickness=1;
dbgDraw.m_drawFlags=b2DebugDraw.e_shapeBit;
m_world.SetDebugDraw(dbgDraw);
// debug draw end
// ground
bodyDef.position.Set(10, 12);
polygon.SetAsBox(30, 3);
polygon.density=0;
polygon.friction=0.3;
polygon.restitution=0.2;
body=m_world.CreateBody(bodyDef);
body.CreateShape(polygon);
body.SetMassFromShapes();
// circle
bodyDef.position.Set(3,5);
circleDef.radius=2;
circleDef.density=1;
circleDef.friction=0.5;
circleDef.restitution=0.2;
body=m_world.CreateBody(bodyDef);
body.CreateShape(circleDef);
body.SetMassFromShapes();
// box
bodyDef.position.Set(13, 5);
polygon.SetAsBox(2, 2);
polygon.density=1;
polygon.friction=0.5;
polygon.restitution=0.2;
body=m_world.CreateBody(bodyDef);
body.CreateShape(polygon);
body.SetMassFromShapes();
// triangle
bodyDef.position.Set(13,3);
polygon.vertexCount=3;
polygon.vertices[0].Set(0,-2);
polygon.vertices[1].Set(2,2);
polygon.vertices[2].Set(-2,2);
polygon.density=1;
polygon.friction=0.5;
polygon.restitution=0.2;
body=m_world.CreateBody(bodyDef);
body.CreateShape(polygon);
body.SetMassFromShapes();
// custom shape
bodyDef.position.Set(8,4);
polygon.vertexCount=5;
polygon.vertices[0].Set(0,-2);
polygon.vertices[1].Set(2,0);
polygon.vertices[2].Set(1,2);
polygon.vertices[3].Set(-1,2);
polygon.vertices[4].Set(-2,0);
polygon.density=1;
polygon.friction=0.5;
polygon.restitution=0.2;
body=m_world.CreateBody(bodyDef);
body.CreateShape(polygon);
body.SetMassFromShapes();
//
addEventListener(Event.ENTER_FRAME, Update, false, 0, true);
stage.addEventListener(KeyboardEvent.KEY_DOWN, key_down);
stage.addEventListener( KeyboardEvent.KEY_UP, key_up);
stage.addEventListener(MouseEvent.MOUSE_DOWN, GetBodyAtMouse);
}
// detecting if the player pressed SPACE
public function key_down(event:KeyboardEvent):void {
if (event.keyCode==32) {
space_pressed=true;
}
}
// detecting if the player released SPACE
public function key_up(event:KeyboardEvent):void {
if (event.keyCode==32) {
space_pressed=false;
}
}
//
public function GetBodyAtMouse(e:MouseEvent):b2Body {
var mult:Number=0.9;
if (space_pressed) {
mult=1.1;
}
var mouseXWorldPhys = (mouseX)/30;
var mouseYWorldPhys = (mouseY)/30;
mousePVec.Set(mouseXWorldPhys, mouseYWorldPhys);
var aabb:b2AABB = new b2AABB();
aabb.lowerBound.Set(mouseXWorldPhys - 0.001, mouseYWorldPhys
- 0.001);
aabb.upperBound.Set(mouseXWorldPhys + 0.001, mouseYWorldPhys
+ 0.001);
var k_maxCount:int=10;
var shapes:Array = new Array();
var count:int=m_world.Query(aabb,shapes,k_maxCount);
var body:b2Body=null;
for (var i:int = 0; i < count; ++i) {
var tShape:b2Shape=shapes[i] as b2Shape;
var inside:Boolean=tShape.TestPoint(tShape.GetBody().GetXForm(),mousePVec);
if (inside) {
body=tShape.GetBody();
break;
}
}
// if I selected a STATIC body...
if (body&&! body.IsStatic()) {
var s:b2Shape=body.GetShapeList();
var type:int=s.GetType();
switch (type) {
case 0 :
// I know it's a circle, so I am creating a b2CircleShape variable
var circle:b2CircleShape=body.GetShapeList() as b2CircleShape;
// getting the radius..
var r=circle.GetRadius();
// removing the circle shape from the body
body.DestroyShape(circle);
// creating a new circle shape
var circleDef:b2CircleDef;
circleDef = new b2CircleDef();
// calculating new radius
circleDef.radius=r*mult;
circleDef.density=1.0;
circleDef.friction=0.5;
circleDef.restitution=0.2;
// attach the shape to the body
body.CreateShape(circleDef);
// determine new body mass
body.SetMassFromShapes();
break;
case 1 :
// now I know it's a polygon
var poly:b2PolygonShape=body.GetShapeList() as b2PolygonShape;
// UNIVERSAL POLYGON SCALING ROUTINE THANX TO ILYA
var vertex_num:int=poly.GetVertexCount();
var vertex_array:Array=poly.GetVertices();
for each (var vert:b2Vec2 in vertex_array) {
vert.Multiply(mult);
}
body.DestroyShape(poly);
var new_shape:b2PolygonDef = new b2PolygonDef();
new_shape.vertexCount=vertex_num;
new_shape.vertices=vertex_array;
new_shape.friction=0.5;
new_shape.density=1;
new_shape.restitution=0.2;
body.CreateShape(new_shape);
body.SetMassFromShapes();
break;
}
}
return body;
}
public function Update(e:Event):void {
m_world.Step(m_timeStep, m_iterations);
}
}
}
And this is the result:
Left click on a static body with the mouse to shrink it, left click + SPACE to expand it.
Next time... player, goal and "mass energy".
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