Talking about Crush the Castle game, Actionscript 3, Box2D and Flash.
We got it.
After the first catapult prototype and the “slippery wheels” sequel, this is a version with realistic movement and a lot cleaner code.
To add realistic movement I defined friction and restitution, making useless the CreateFixture2 function and widely using the more appropriate CreateFixture one.
This way I have full control on fixtures, while in the old way I could only define their masses.
This is the result:
Left and right to move, spacebar to fire
And this is the code:
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.KeyboardEvent;
import Box2D.Dynamics.*;
import Box2D.Collision.*;
import Box2D.Collision.Shapes.*;
import Box2D.Common.Math.*;
import Box2D.Dynamics.Joints.*;
public class main extends Sprite {
public var world:b2World=new b2World(new b2Vec2(0,10.0),true);
public var world_scale:int=30;
var catapult_chassis_body:b2Body;
var catapult_arm_body:b2Body;
var rear_wheel_body:b2Body;
var front_wheel_body:b2Body;
var arm_revolute_joint:b2RevoluteJoint;
var front_wheel_revolute_joint:b2RevoluteJoint;
var rear_wheel_revolute_joint:b2RevoluteJoint;
var left_key_pressed:Boolean=false;
var right_key_pressed:Boolean=false;
public function main():void {
debug_draw();
the_ground();
the_catapult_body();
the_catapult_arm();
the_catapult_motor();
the_wheels();
the_wheel_motors();
the_cannonball();
addEventListener(Event.ENTER_FRAME, update);
stage.addEventListener(KeyboardEvent.KEY_DOWN, key_down);
stage.addEventListener(KeyboardEvent.KEY_UP, key_up);
}
public function the_cannonball():void {
var cannonball:b2BodyDef= new b2BodyDef();
cannonball.position.Set(90/world_scale, 90/world_scale);
cannonball.type=b2Body.b2_dynamicBody;
var ball:b2CircleShape=new b2CircleShape(10/world_scale);
var cannonball_fixture:b2FixtureDef = new b2FixtureDef();
cannonball_fixture.shape=ball;
cannonball_fixture.friction=0.9;
cannonball_fixture.density=20;
cannonball_fixture.restitution=0.5;
var the_cannonball_itself:b2Body=world.CreateBody(cannonball);
the_cannonball_itself.CreateFixture(cannonball_fixture);
}
public function the_wheel_motors():void {
var front_wheel_joint:b2RevoluteJointDef = new b2RevoluteJointDef();
front_wheel_joint.enableMotor=true;
front_wheel_joint.Initialize(catapult_chassis_body, front_wheel_body,new b2Vec2(0,0));
front_wheel_joint.localAnchorA=new b2Vec2(80/world_scale,0);
front_wheel_joint.localAnchorB=new b2Vec2(0,0);
front_wheel_revolute_joint=world.CreateJoint(front_wheel_joint) as b2RevoluteJoint;
front_wheel_revolute_joint.SetMaxMotorTorque(1000000);
//
var rear_wheel_joint:b2RevoluteJointDef = new b2RevoluteJointDef();
rear_wheel_joint.enableMotor=true;
rear_wheel_joint.Initialize(catapult_chassis_body, rear_wheel_body,new b2Vec2(0,0));
rear_wheel_joint.localAnchorA=new b2Vec2(-80/world_scale,0);
rear_wheel_joint.localAnchorB=new b2Vec2(0,0);
rear_wheel_revolute_joint=world.CreateJoint(rear_wheel_joint) as b2RevoluteJoint;
rear_wheel_revolute_joint.SetMaxMotorTorque(1000000);
}
public function the_wheels():void {
var rear_wheel:b2BodyDef= new b2BodyDef();
rear_wheel.position.Set(250/world_scale, 200/world_scale);
rear_wheel.type=b2Body.b2_dynamicBody;
var rear_wheel_shape:b2CircleShape=new b2CircleShape(40/world_scale);
var rear_wheel_fixture:b2FixtureDef = new b2FixtureDef();
rear_wheel_fixture.shape=rear_wheel_shape;
rear_wheel_fixture.friction=0.9;
rear_wheel_fixture.density=30;
rear_wheel_fixture.restitution=0.1;
rear_wheel_body=world.CreateBody(rear_wheel);
rear_wheel_body.CreateFixture(rear_wheel_fixture);
//
var front_wheel:b2BodyDef= new b2BodyDef();
front_wheel.position.Set(450/world_scale, 200/world_scale);
front_wheel.type=b2Body.b2_dynamicBody;
var front_wheel_shape:b2CircleShape=new b2CircleShape(40/world_scale);
var front_wheel_fixture:b2FixtureDef = new b2FixtureDef();
front_wheel_fixture.shape=front_wheel_shape;
front_wheel_fixture.friction=0.9;
front_wheel_fixture.density=30;
front_wheel_fixture.restitution=0.1;
front_wheel_body=world.CreateBody(front_wheel);
front_wheel_body.CreateFixture(front_wheel_fixture);
}
public function the_catapult_motor():void {
var arm_joint:b2RevoluteJointDef = new b2RevoluteJointDef();
arm_joint.enableMotor=true;
arm_joint.enableLimit=true;
arm_joint.Initialize(catapult_chassis_body, catapult_arm_body,new b2Vec2(0,0));
arm_joint.localAnchorA=new b2Vec2(-80/world_scale,-90/world_scale);
arm_joint.localAnchorB=new b2Vec2(60/world_scale,0);
arm_revolute_joint=world.CreateJoint(arm_joint) as b2RevoluteJoint;
arm_revolute_joint.SetMotorSpeed(1000);
arm_revolute_joint.SetLimits(-Math.PI,Math.PI/3);
arm_revolute_joint.SetMaxMotorTorque(1);
}
public function the_catapult_arm():void {
var catapult_arm:b2BodyDef = new b2BodyDef();
catapult_arm.allowSleep=false;
catapult_arm.position.Set(210/world_scale,110/world_scale);
catapult_arm.type=b2Body.b2_dynamicBody;
var arm_part:b2PolygonShape = new b2PolygonShape();
arm_part.SetAsOrientedBox(150/world_scale, 10/world_scale, new b2Vec2(0,0),0);
var arm_part_fixture:b2FixtureDef = new b2FixtureDef();
arm_part_fixture.shape=arm_part;
arm_part_fixture.friction=0.9;
arm_part_fixture.density=5;
arm_part_fixture.restitution=0.1;
var stopper:b2PolygonShape = new b2PolygonShape();
stopper.SetAsOrientedBox(10/world_scale, 20/world_scale, new b2Vec2(-140/world_scale,-30/world_scale),0);
var stopper_fixture:b2FixtureDef = new b2FixtureDef();
stopper_fixture.shape=stopper;
stopper_fixture.friction=0.9;
stopper_fixture.density=10;
stopper_fixture.restitution=0.1;
catapult_arm_body=world.CreateBody(catapult_arm);
catapult_arm_body.CreateFixture(arm_part_fixture);
catapult_arm_body.CreateFixture(stopper_fixture);
}
public function the_catapult_body():void {
var catapult_body:b2BodyDef = new b2BodyDef();
catapult_body.position.Set(350/world_scale,200/world_scale);
catapult_body.type=b2Body.b2_dynamicBody;
var main_part:b2PolygonShape = new b2PolygonShape();
main_part.SetAsOrientedBox(125/world_scale, 20/world_scale, new b2Vec2(0,0),0);
var chassis_fixture:b2FixtureDef = new b2FixtureDef();
chassis_fixture.shape=main_part;
chassis_fixture.friction=0.9;
chassis_fixture.density=50;
chassis_fixture.restitution=0.1;
var fixed_arm:b2PolygonShape = new b2PolygonShape();
fixed_arm.SetAsOrientedBox(20/world_scale, 60/world_scale, new b2Vec2(-80/world_scale,-40/world_scale),0);
var fixed_arm_fixture:b2FixtureDef = new b2FixtureDef();
fixed_arm_fixture.shape=fixed_arm;
fixed_arm_fixture.friction=0.9;
fixed_arm_fixture.density=1;
fixed_arm_fixture.restitution=0.1;
catapult_chassis_body=world.CreateBody(catapult_body);
catapult_chassis_body.CreateFixture(chassis_fixture);
catapult_chassis_body.CreateFixture(fixed_arm_fixture);
}
public function the_ground():void {
var ground:b2BodyDef= new b2BodyDef();
ground.position.Set(250/world_scale, 400/world_scale);
var my_box:b2PolygonShape = new b2PolygonShape();
my_box.SetAsBox(1000/world_scale, 15/world_scale);
var ground_fixture:b2FixtureDef = new b2FixtureDef();
ground_fixture.shape=my_box;
ground_fixture.friction=0.9;
ground_fixture.restitution=0.1;
var the_ground_itself:b2Body=world.CreateBody(ground);
the_ground_itself.CreateFixture(ground_fixture);
}
public function key_up(event:KeyboardEvent):void {
switch (event.keyCode) {
case 39 :
right_key_pressed=false;
break;
case 37 :
left_key_pressed=false;
break;
}
}
public function key_down(event:KeyboardEvent):void {
switch (event.keyCode) {
case 39 :
right_key_pressed=true;
left_key_pressed=false;
break;
case 37 :
left_key_pressed=true;
right_key_pressed=false;
break;
case 32 :
arm_revolute_joint.SetMaxMotorTorque(10000);
break;
}
}
public function debug_draw():void {
var debug_draw:b2DebugDraw = new b2DebugDraw();
var debug_sprite:Sprite = new Sprite();
addChild(debug_sprite);
debug_draw.SetSprite(debug_sprite);
debug_draw.SetDrawScale(world_scale);
debug_draw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);
debug_draw.SetFillAlpha(0.5);
world.SetDebugDraw(debug_draw);
}
public function set_motor_speed():void {
var current_speed:Number;
if (right_key_pressed) {
current_speed=1;
}
if (left_key_pressed) {
current_speed=-1;
}
if (! right_key_pressed&&! left_key_pressed) {
current_speed=rear_wheel_revolute_joint.GetMotorSpeed()*0.9;
if (Math.abs(current_speed)<0.1) {
current_speed=0;
}
}
rear_wheel_revolute_joint.SetMotorSpeed(current_speed);
front_wheel_revolute_joint.SetMotorSpeed(current_speed);
}
public function update(e:Event):void {
set_motor_speed();
world.Step(1/30,10,10);
world.ClearForces();
world.DrawDebugData();
}
}
}
No need to download, just cut and paste on the first catapult prototype.
Next time, full comments and some other interesting features...
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