Strange movements box2d[SOLVED]

[AdrianN]

Hi, I'm making a top down game with box2d, at the moment I have a problem with a strange movement, with two bodies collides between theirs. This event appear only with I create a extra fixture (fixture_melee).

Fixture_melee is a sensor to simulate a melee attack.

To move the body I use only setLinearVelocity , velocity,x and velocity.y is print in the screen.

Code: Select all

--modelo.lua (model class)
self.collider=py.newBody(self.entidades.world,x,y,"dynamic")
self.collider:setMass(10)
self.shape=py.newCircleShape(r)
self.fixture=py.newFixture(self.collider,self.shape)
self.fixture:setGroupIndex( -self.creador )
self.fixture:setUserData( {data="personaje",obj=self} )

self.collider:setInertia( 0 )
self.collider:setGravityScale( 0 )

self.ox,self.oy=self.collider:getX(),self.collider:getY()

self.rad=self.shape:getRadius()
self.shape_escudo=py.newCircleShape(r*2.5)
self.fixture_escudo=py.newFixture(self.collider,self.shape_escudo)
self.fixture_escudo:setSensor( true )
self.fixture_escudo:setGroupIndex( -self.creador )
self.fixture_escudo:setUserData( {data="escudo",obj=self}  )
	
--Radian.lua
--inicializate model class
Modelo.init(self,x,y,20)

self.shape_melee=py.newRectangleShape(50,0,100,75)
self.fixture_melee=py.newFixture(self.collider,self.shape_melee)
self.fixture_melee:setSensor( true )

self.fixture_melee:setGroupIndex( -self.creador )
self.fixture_melee:setUserData( {data="melee",obj=self}  )	
	

[pgimeno]

I can't tell for sure, but it seems to me that you need fixed rotation. Try self.collider:setFixedRotation(true).

Alternatively, you can set the density of the melee fixture to 0 and call resetMassData on the body.

My opinion is that the eccentricity of the melee sensor causes collisions to introduce angular momentum, due to the displacement of the centre of mass. Then setAngle interferes with the momentum calculation, causing the momentum velocity to be applied in the wrong direction.

[AdrianN]

I can't tell for sure, but it seems to me that you need fixed rotation. Try self.collider:setFixedRotation(true).

Alternatively, you can set the density of the melee fixture to 0 and call resetMassData on the body.

My opinion is that the eccentricity of the melee sensor causes collisions to introduce angular momentum, due to the displacement of the centre of mass. Then setAngle interferes with the momentum calculation, causing the momentum velocity to be applied in the wrong direction.

Thanks pgimeno, self.collider:setFixedRotation(true) work fine.