Here's how to find the distance between 2 points

Comments

• techdojo Guru

  November 2012 edited November 2012

  You can avoid the nasty (expensive) math.sqrt function by just pre-squaring the distance you want to check against,
  
  so if you want to check if an object is within say 25 pixels instead of checking if self.distance <= 25, just set self.distance = ((self.dx * self.dx) + (self.dy * self.dy)) and then check if self.distance <= (25*25).
  
  If you've got a lot of checks to do the savings will start to mount up.
  
  Also - there used to be a quick hack in the old 8/16bit days where you could "guestimate" distance to +/-10% by calculating dx and dy as above and then simply using the max of dx or dy plus half the min of dx or dy, using a single bit shift right the "half" practically came for free.
  

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• Tom2012 Guru

  November 2012 edited November 2012

  Hey techdojo
  
  That works perfectly. Thank you.
  
  For anyone interested, here's my example:
  
  (self.maxLength is the max length in this example)

  -- Work out the distance from hero   self.dx = self:getX() - self.scene.hero:getX(); self.dy = self:getY() - self.scene.hero:getY();   self.distance = (self.dx*self.dx)+(self.dy*self.dy)   -- Distance went over maxLength   if(self.distance >= (self.maxLength*self.maxLength)) then   -- do something here   end

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• Teranth Member

  November 2012

  @Tom2012 thanks for the share

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• talis Guru

  November 2012

  Thanks for the share guys:-)
  

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