cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   jp16
   Member

   I am trying to move a sprite at a constant speed across the screen when the user holds a button down but does not release it.

   This is what I have done so far.

   1. Created a boolean variable, beginMoving = false
   2. On my ccTouchesBegan event method I set beginMoving to true
   3. Inside my game tick, I check to see if beginMoving is true, if true I use MoveTo to move the sprite +10 pixels. If false, I simply do not move the sprite.

   Is there a better approach than this? The movement looks a little jerky though barely noticeable.

   Posted 2 years ago #
2. 

   ob1
   Member

   Two problems:

   The numbers of pixel you move should not be fixed but a factor of the "dt" parameter in the "tick" method:
   

   position.x += speedVector.x*dt;
   position.y += speedVector.y*dt;

   Second, check this:

   http://code.google.com/p/cocos2d-iphone/issues/detail?id=399&can=1&q=int&colspec=ID Type Status Priority Milestone Component Owner Summary

   Posted 2 years ago #
3. 

   coolman
   Member

   See also the sample that comes with the SDK "MoveMe"

   Posted 2 years ago #
4. 

   jp16
   Member

   Thanks ob1, I tried looking up how to use a speed vector but I couldn't find anything. What is a speed vector?

   Posted 2 years ago #
5. 

   jp16
   Member

   "position.x += speedVector.x*dt;
   position.y += speedVector.y*dt;"

   I'm still having trouble understanding this, how is it possible to move a sprite by changing its position.x and y values?

   Posted 2 years ago #
6. 

   pabloruiz55
   Member

   To move a sprite is that, changing its position vector.

   if each frame you change its position like position.x += speedVector.x*dt; it will be moving to the right. How much? whatever the value of speedVector.x is...

   You could also use cocos2d moveTo and moveBy to move an sprite. Check the examples. ;)

   Posted 2 years ago #
7. 

   ob1
   Member

   Sorry, I was a bit misleading since in English what I call "speed vector" is called velocity:

   http://en.wikipedia.org/wiki/Velocity

   I think pabloruiz55 explained it well.

   Each sprite has a "position" property. like:

   mypsrite.position

   Since it's a CGpoint, it has a x and y value:

   mypsrite.position.x
   mypsrite.position.y

   Velocity will be another CGPoint that you define yourself with the velocity you want.

   Posted 2 years ago #
8. 

   jp16
   Member

   Thanks ob1, pabloruiz55!

   What I understand is that I would need to account for the delta time between each tick and calculate that into my movement accordingly. There is nothing wrong with using the MoveBy action as long as I account for the delta time.

   Posted 2 years ago #

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