cocos2d for iPhone

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

1. 

   XyrisKenn
   Member

   Hi, (cross-posting with the Box 2D forum)

   Trying combinations of friction, density, frequencyHz and damping to reduce the inherent 'springiness' of mousejoints, I've not been able to make a player piece follow exactly the user's touch point, especially if they slide it around in concentric circles.

   Is there any way to eliminate the 'lazy following' effect of the mousejoint?

   I'm creating an iphone game which can become fast-paced, and I need the player pieces to tightly follow the touch point on-screen.

   Thanks for your time and help, it's appreciated!

   Posted 2 years ago #
2. 

   badawe
   Member

   @XYrisKenn To do something like that, i can figure out 2 simples ways:
   1º - Remove the body of the world at the moment of the touchBegan, and just move the position you your sprite in the TouchMoves, and in the TouchesEnded you create the body again at the exaclty position of your draggable sprite.
   Cons: You loose the colision in the drag
   2º - Forcing the body with the setTransform to desired position of your touch.
   Cons: This is not realy indicated, becouse force bodys you can loose some steps at the world step.

   Posted 2 years ago #
3. 

   XyrisKenn
   Member

   @badawe, Thank you for suggestions. My project is interesting in that it needs strict touch matching and also needs to respond to physics while dragging. I'm studying the Box2D source, in hope of modifying it, although I'm new to Obj-c.

   Maybe it's possible to alter or combine some functions of mouseJoints and prismatic joints code directly to allow both axis of movement without the soft joint calculations? For example, an option to 'set mousejoint to '.isRigid', analogous to setting .fixedRotation in a body would be fantastic.

   Posted 2 years ago #
4. 

   XyrisKenn
   Member

   It's becoming clear that mouseJoint is meant to apply force to an object, for interesting reactions in the testbed, like a weight on a rubber band. So it's not really a good fit for following a player's touchpoint on the screen.

   Reading Apress's iPhone Cool Projects the author mentions a cpMouse function in Chipmunk, where momentum is transfered to the object when a player slides it around the screen.

   Does Box2D have something similar, perhaps SetTransform?

   Posted 2 years ago #
5. 

   eshirt
   Member

   XyrisKenn, once again it looks like we're trying to do the same thing. :) I've been trying to get this figured out for weeks and I've since given up, letting bodies swing around the joint. To detract from the effect (and the residual motion), I've set both the linear and angular velocity to 0 during the dragging action. I'm not sure it helped, but I also set a very large mass and friction value to each object.

   I'll keep looking of course, and update if I find another way.

   Posted 2 years ago #
6. 

   XyrisKenn
   Member

   I'm sort of at the same decision point, I've spent a few weeks learning Box2d and trying different solutions for multitouch and rigid joints, but my level of knowledge of obj-c and Box2D's mouseJoint limitations are giving me reason to put Box2D physics aside for the moment and work on the game structure itself :)
   Perhaps in the meantime one of us will come up with a solution.

   I like the motion results of Box2D but integrating it with classes, mouse following and multitouch with full physics is proving very difficult.

   While searching for 'box2d mouse movement' on google, I came across a google code project which is building multitouch into box2d somehow: http://code.google.com/p/reactickles/source/detail?r=16

   Perhaps the authors of that code might have ideas.

   Posted 2 years ago #

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