box2d (LiquidFun) - get shape (polygon) from fixture

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• MoKaLux Member

  December 2020 edited December 2020

  Assuming you have a class (a player class, ...) you can access its shape or anything using self.

  -- sprite & bitmap self.bitmap = Bitmap.new(self.spritesheetimgs[1]) -- starting bmp texture -- body self.body = xworld:createBody { type = b2.DYNAMIC_BODY } self.body.lives = 3 -- body fixture self.shape = b2.CircleShape.new(0, 0, 16) -- (centerx, centery, radius) self.fixture = self.body:createFixture { shape = self.shape, density = xdensity or 1, restitution = xrestitution or 0, friction = xfriction or 1 }

  Hope this helps.

  my growING GIDEROS github repositories: https://github.com/mokalux?tab=repositories

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• sphinxx Member

  December 2020

  In my case self.shape is a polygon. The problem is that I'm not sure if self.shape follows body rotation in game loop. Even if it does, I would need polygon in form of {x1,y1,x2,y2....xn,yn}, but type(self.shape) returns 'userdata' - probably kind of C pointer. Useless for me.
  thanxx anyway
  

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• MoKaLux Member

  December 2020 edited December 2020

  I believe the shape follows the rotation of the body.
  A couple of things you can try:
  - try to store your {x1,y1,x2,y2....xn,yn} is a self.table so you can access it
  - or you could try unpack()

  stage:addEventListener(Event.ENTER_FRAME, function() -- edit the step values if required. These are good defaults! world:step(1/60, 8, 3) ball:setPosition(ball.body:getPosition()) ball:setRotation(math.rad(ball.body:getAngle())) -- ROTATION HERE end)

  https://wiki.gideros.rocks/index.php/B2.Body

  my growING GIDEROS github repositories: https://github.com/mokalux?tab=repositories

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• sphinxx Member

  December 2020 edited December 2020

  ok, let's assume the shape is updated according to body rotation/position.
  But still I don't know the data structure of shape ball.poly for conversion to {x1,y1,x2,y2...} later in onEnterFrame loop.
  
  local poly = {-20,-20, 40,-20, 50,20, -25,30}
  ball.body = world:createBody{type = b2.DYNAMIC_BODY}
  ball.poly = b2.PolygonShape.new()
  ball.poly:set(unpack(poly))
  ball.fixture = ball.body:createFixture{shape = ball.poly, density = 1.0, friction = 0.1, restitution = 0.2}
  
  ...anyway, I already did it in other way.
  
  

  Likes: MoKaLux

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