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libgdxbox2d

Body Still detect collision after setting maskbit and category

I have set maskbits and categorybits of my body. But why collision is still detected between object that is not supposed to be detected?

Body 1:

    BodyDef def = new BodyDef();
    FixtureDef fixtureDef = new FixtureDef();

    def.type = BodyDef.BodyType.DynamicBody;
    def.position.set( 5, 2);

    CircleShape circleShape = new CircleShape();
    circleShape.setRadius(getWidth() /GC.UNITS_PER_METER /7);

    fixtureDef.shape = circleShape;
    fixtureDef.density = 1f;
    fixtureDef.friction = 1;
    fixtureDef.filter.categoryBits = GC.CATEGORY_MONSTER_MOUTH;
    fixtureDef.filter.maskBits = GC.MASK_MONSTER_MOUTH;

    Body box = world.createBody(def);
    box.createFixture(fixtureDef);
    circleShape.dispose();

    sensorBody= box;
    sensorBody.setFixedRotation(true);
    sensorBody.setAwake(true);
    sensorBody.setUserData(this);

Body 2:

    BodyDef def = new BodyDef();
    FixtureDef fixtureDef = new FixtureDef();

    def.type = BodyDef.BodyType.DynamicBody;
    def.position.set(getX() - (getWidth()* getScaleX()) , getY() - (getHeight() * getScaleY()));

    CircleShape circleShape = new CircleShape();
    circleShape.setRadius(box2dWidth/2);

    fixtureDef.shape = circleShape;
    fixtureDef.density = 1f;
    fixtureDef.friction=0.5f;
    fixtureDef.filter.categoryBits = GC.CATEGORY_MONSTER;
    fixtureDef.filter.maskBits = GC.MASK_MONSTER;
    Body box = world.createBody(def);
    box.createFixture(fixtureDef);
    polygonShape.dispose();

    body = box;
    body.setAwake(true);
    body.setUserData(this);
    body.setAngularDamping(4);
    body.setFixedRotation(true);

My categories details:

public static final short CATEGORY_ARROW = 0x0001; // 0000000000000001 in binary
public static final short CATEGORY_MONSTER = 0x0002; // 0000000000000010 in binary
public static final short CATEGORY_SCENERY = 0x0004; // 0000000000000100 in binary
public static final short CATEGORY_GRAVEYARD = 0x0008; // 0000000000000100 in binary
public static final short CATEGORY_PENGUIN = 0X0016;
public static final short CATEGORY_FISH = 0x0032;
public static final short CATEGORY_MONSTER_MOUTH = 0x0064;

public static final short MASK_ARROW = CATEGORY_MONSTER | CATEGORY_SCENERY; 
public static final short MASK_MONSTER = CATEGORY_ARROW | CATEGORY_SCENERY ; 
public static final short MASK_PENGUIN = CATEGORY_SCENERY | CATEGORY_MONSTER; 
public static final short MASK_FISH = CATEGORY_MONSTER_MOUTH| CATEGORY_SCENERY; 
public static final short MASK_GRAVEYARD = CATEGORY_SCENERY;
public static final short MASK_MONSTER_MOUTH = CATEGORY_FISH | CATEGORY_SCENERY;

Body1 and body2 are not supposed colliding each other, but I failed to acheive it by setting maskbits and categorybits. Anyone please help.

Solution

  • The CATEGORY values in Hex are wrong. Currently the values of your CATEGORYs are:

    public static final short CATEGORY_ARROW = 0x0001; // 1 in binary
public static final short CATEGORY_MONSTER = 0x0002; // 10 in binary
public static final short CATEGORY_SCENERY = 0x0004; // 100 in binary
public static final short CATEGORY_GRAVEYARD = 0x0008; // 1000 in binary
public static final short CATEGORY_PENGUIN = 0X0016; // 10110 in binary
public static final short CATEGORY_FISH = 0x0032; // 110010 in binary
public static final short CATEGORY_MONSTER_MOUTH = 0x0064; // 1100100 in binary

    So MASK_MONSTER = CATEGORY_MONSTER | CATEGORY_SCENERY = 110 in binary
    And CATEGORY_MONSTER_MOUTH = 1100100 in binary

    Finally, MASK_MONSTER | CATEGORY_MONSTER_MOUTH will match because it results in 100

    Your problem is that your count up in Hex is wrong you must write:

    public static final short CATEGORY_ARROW = 0x0001; // 1 in binary
public static final short CATEGORY_MONSTER = 0x0002; // 10 in binary
public static final short CATEGORY_SCENERY = 0x0004; // 100 in binary
public static final short CATEGORY_GRAVEYARD = 0x0008; // 1000 in binary
public static final short CATEGORY_PENGUIN = 0X0010; // 10000 in binary
public static final short CATEGORY_FISH = 0x0020; // 100000 in binary
public static final short CATEGORY_MONSTER_MOUTH = 0x0040; // 1000000 in binary

    After that comes 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000 etc.