Rotate and Move

Comments

• techdojo Guru

  February 2013 Accepted Answer

  You need to calculate a new x,y offset from your current position using basic 2D trig. Something like

  local cx,cy -- current x, y pos local xo,yo -- x, y offset local angle -- current facing angle local speed -- movement speed / distance to move   xo = math.sin(math.rad(angle)) * speed yo = 0 - math.cos(math.rad(angle)) * speed cx = cx + xo cy = cy + yo   self:setRotation(angle) self:setPosition(cx,cy)

  I might have got the sin / cos the wrong way round - can never remember (also yo is negative because y=0 is top left not bottom left), and don't forget that sin / cos work in radians not degrees, so you might want to calc that first.

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• Cyberience Member

  February 2013 edited February 2013

  Update, since I got it working, here is my working prototype. Angle of direction of the sprite/movieclip,and the x,y potion update based on that angle, so others should find it easy to follow and make changes, such as randomising the position or angles.

  function MovieSprite:running(event) local cx, cy = self:getX() ,self:getY() -- current x, y pos local xo,yo -- x, y offset self.speed = self.speed or 1 -- movement speed / distance to move local Radtheta = self.angle * math.pi/180 xo = math.cos(Radtheta) * self.speed yo = math.sin(Radtheta) * self.speed cx = cx + xo cy = cy + yo   self:setRotation(self.angle) self:setPosition(cx,cy)   end

  All I want to figure out now is if there is a way to make this work with the tween, Rather than have a specific location to fly to, just to travel in random patterns in a rough direction

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• techdojo Guru

  February 2013 Accepted Answer

  If you mean do you want to pick some random coord on the screen, and have the sprite move to that location?
  
  If so the process is a little different, as you already know the position, it's the angle you need to calculate.
  
  What you do is pick a position on screen relative to your current position, then use the math.atan2() function with the relative offset, this will return the angle from where you are now to where you want to go.
  
  You should be able to plug these numbers into a MovieClip object and have your sprite automatically update itself as the MovieClip runs, failing that you just perform the movement each step as above.
  
  Note - Once you know the x,y offsets you only need to calculate the direction angle once (it'll never change - although the "facing" direction will if you want to rotate smoothly) and also the x,y frame step value is simply the offset (distance to move) / number of frames to give a constant speed across the distance.

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  #MakeABetterGame! "Never give up, Never NEVER give up!" - Winston Churchill

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