Java-Gaming.org    
Featured games (81)
games approved by the League of Dukes
Games in Showcase (498)
Games in Android Showcase (115)
games submitted by our members
Games in WIP (562)
games currently in development
News: Read the Java Gaming Resources, or peek at the official Java tutorials
 
    Home     Help   Search   Login   Register   
Pages: [1]
  ignore  |  Print  
  [LibGDX] Body size and mass with Box2D  (Read 396 times)
0 Members and 1 Guest are viewing this topic.
Offline sirkarpfen

Junior Member


Medals: 2
Exp: 2 years



« Posted 2013-08-02 11:02:07 »

I recently encountered a problem when using different sizes (therefore masses).

I am developing a breakout-like game. I need different sized balls that move in the same velocity as if they are equally sized. In other words, they should be dynamic bodies but "ignore mass" when applying an impulse on them. Is there a way to accomplish this?

That is the Ball class:

1  
2  
3  
4  
5  
6  
7  
8  
9  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
26  
27  
28  
29  
30  
31  
32  
33  
34  
35  
36  
37  
38  
39  
40  
41  
42  
43  
44  
45  
46  
47  
48  
49  
50  
51  
52  
53  
54  
55  
56  
57  
58  
59  
60  
61  
62  
63  
64  
65  
66  
67  
68  
69  
70  
71  
72  
73  
74  
75  
76  
77  
78  
79  
80  
81  
82  
83  
public class Ball extends Entity {

   private Texture texture;
   private Body body;
   public Body getBody() { return body; }
   
   private float radius;
   public float getRadius() { return radius; }
   private Directions direction = Directions.STOP;
   public void setDirection(Directions left) { direction = left; }
   
   private boolean started = false;
   public void setStarted(boolean started) { this.started = started; }
   public boolean hasStarted() { return started; }
   
   public Ball(float x, float y) {
      super(x,y);
      radius = 10/pixel_to_meter;
      this.createBody();
   }
   
   public Ball(float x, float y, float radius) {
      super(x,y);
      this.radius = radius;
      this.createBody();
   }
   
   @Override
   public void createBody() {
      texture = new Texture(Gdx.files.internal("data/sprites/ballGrey.png"));
      body = BodyFactory.createCircleBody(
            new Vector2(x, y), radius, BodyType.DynamicBody, FixtureType.CUSTOM);
      BodyFactory.createFixture(
            body, BodyFactory.createCircleShape(radius), new float[] {1f,0f,1f}, false, (short)1);
      body.setFixedRotation(false);
      body.setUserData(this);
   }
   
   @Override
   public void render(SpriteBatch spriteBatch) {
      spriteBatch.begin();
      spriteBatch.draw(texture, (body.getPosition().x-radius)*pixel_to_meter, (body.getPosition().y-radius)*pixel_to_meter);
      spriteBatch.end();
   }
   
   public void move() {
      if(!started) {
         switch (direction) {
         
         case LEFT:
            body.setLinearVelocity(-Paddle.VELOCITY,0);
            break;
         case RIGHT:
            body.setLinearVelocity(Paddle.VELOCITY,0);
            break;
         case STOP:
            body.setLinearVelocity(0,0);
            break;
         }
      }
   }
   
   public void start() {
      body.setLinearVelocity(0,0);
      Random generator = new Random();
      if(generator.nextBoolean()) {
         body.applyLinearImpulse(new Vector2(-0.06f,0.06f), body.getPosition());
      } else {
         body.applyLinearImpulse(new Vector2(0.06f,0.06f), body.getPosition());
      }
     
      System.out.println(body.getLinearVelocity().x + ", " + body.getLinearVelocity().y);
   }
   public void destroy() {
      World world = BlockGame.getWorld();
      world.destroyBody(body);
      this.started = false;
   }
   public void lockMovement() {
      body.setLinearVelocity(0,0);
   }
   
}



The BodyFactory class is just a wrapper for simplifying the process of creating bodies (If needed i will edit it here too Smiley).

PS: Is there a way to spoiler the code? I tried it with the [.spoiler] tags but that didn't do it...
Offline sirkarpfen

Junior Member


Medals: 2
Exp: 2 years



« Reply #1 - Posted 2013-08-02 17:16:36 »

Well i found the solution and it was too easy to find xD.

I just set the density of every Ball to 0 and it behaves as i wanted it to Smiley.
Pages: [1]
  ignore  |  Print  
 
 
You cannot reply to this message, because it is very, very old.

 

Add your game by posting it in the WIP section,
or publish it in Showcase.

The first screenshot will be displayed as a thumbnail.

BurntPizza (25 views)
2014-09-21 02:42:18

BurntPizza (16 views)
2014-09-21 01:30:30

moogie (19 views)
2014-09-21 00:26:15

UprightPath (26 views)
2014-09-20 20:14:06

BurntPizza (29 views)
2014-09-19 03:14:18

Dwinin (44 views)
2014-09-12 09:08:26

Norakomi (74 views)
2014-09-10 13:57:51

TehJavaDev (100 views)
2014-09-10 06:39:09

Tekkerue (50 views)
2014-09-09 02:24:56

mitcheeb (71 views)
2014-09-08 06:06:29
List of Learning Resources
by Longor1996
2014-08-16 10:40:00

List of Learning Resources
by SilverTiger
2014-08-05 19:33:27

Resources for WIP games
by CogWheelz
2014-08-01 16:20:17

Resources for WIP games
by CogWheelz
2014-08-01 16:19:50

List of Learning Resources
by SilverTiger
2014-07-31 16:29:50

List of Learning Resources
by SilverTiger
2014-07-31 16:26:06

List of Learning Resources
by SilverTiger
2014-07-31 11:54:12

HotSpot Options
by dleskov
2014-07-08 01:59:08
java-gaming.org is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑gaming.org
Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines | Managed by Enhanced Four Valid XHTML 1.0! Valid CSS!