cocos2d for iPhone

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

1. 

   iphonemobdev
   Member

   Hi,

   I have developed one game in which i am getting one problem. After colliding ball and shape, some time it getting high speed and it breaking the my border shapes. I tried a lot to figure out that what is the problem but i didn't get.

   Does anyone have idea that what to do?.

   Thanks.

   Posted 2 years ago #
2. 

   vutronic
   Member

   Is your border a cp segment shape? Try to increase the padding like this:

   cpSegmentShapeNew( body, a, b, 4.0f )

   Posted 2 years ago #
3. 

   natanavra
   Member

   Maybe your space step is too fast?
   Try capping it to 1.0/30.0
   Just suggesting here... Not much we can understand from your post

   Posted 2 years ago #
4. 

   iphonemobdev
   Member

   Hi,

   Thanks for reply.

   Same problem, some time ball is getting very high speed. I tried to use 1.0/3.0 but it doesn't help me so much. Actually i have polygon shapes, circles shapes, segment shapes. Ball is moving and colliding with different different shapes. It get high speed after colliding 4-5 times with circles shapes.

   So where should be problem?.

   Thanks.

   Posted 2 years ago #
5. 

   jd
   Member

   Elasticity most likely of one or more of your shapes. If it's too high then I think it will increase your velocity in the opposite direction. Try to lower it.

   Posted 2 years ago #
6. 

   mobilebros
   Moderator

   Is the problem that your ball is getting too fast, (faster than you expect?) or is the problem that your ball is passing thru the shapes you set up?

   If its the second, then this is a known "issue" in chipmunk since chipmunk doesn't do swept collisions, it basically calculates the new point of your ball past the collision point. One way to avoid this is to find where you do this:

   int steps = ?;
   cpFloat dt = deltaTime/(cpFloat)_steps;

   for(int i=0; i<_steps; i++)
   cpSpaceStep(space, dt);

   ... and start increasing steps, this will give the space a more accurate step; However also decreasing your frame rate probably. Hope this helps.

   Posted 2 years ago #
7. 

   iphonemobdev
   Member

   Thanks to all of you.

   I have both problems. Some times ball is getting too much speed and some times, it passing thru the wall shapes also.

   I have given 1.0 Elasticity to the ball and 0.5 to the other shapes.

   See following is the my step methods,

   -(void) step: (ccTime) delta
   {
   int steps = 2;
   cpFloat dt = delta/(cpFloat)steps;

   for (int i = 0; i < steps; i++)
   {
   cpSpaceStep(space, dt);
   }
   cpSpaceHashEach(space->activeShapes, &eachShape, self);
   }

   Thanks.

   Posted 2 years ago #
8. 

   Davin
   Member

   The (ccTime) delta may be different each time.
   So you have to use it to move your sprite.

   Posted 2 years ago #
9. 

   mobilebros
   Moderator

   So the passing through the wall solution would be to change your line from:

   int steps = 2;

   to something like:

   int steps = 10;

   But if you can reduce the actual speed of the ball, that'd be an entirely better solution. Like people have said before, this would most likely be the elasticity, but it could also be in conjunction with differing masses in the collision bodies, make sure that the shapes that collide with the ball don't have some ridiculously large value.

   Posted 2 years ago #
10. 

    iphonemobdev
    Member

    How can i reduce speed of ball. i am getting problems even though i tried int steps = 10;

    Posted 2 years ago #
11. 

    zencoder
    Member

    I'd clamp the values for the location and velocity so that if they exceed a minimum or maximum they get set to the minimum or maximum.

    It doesn't solve the problem of it passing through objects without collisions but it will keep everything on the screen and within a speed limit.

    Posted 2 years ago #

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