cocos2d for iPhone

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

1. 

   jd
   Member

   I'm debating on whether to use box2d or chipmunk or home grown collision detection. I have side scrolling shooting game where the main character can have several different weapon types - including hand melee, shooting and exploding. There will be several enemies on the screen at once. I don't need gravity. The only thing I need is to detect is if one of my weapons hits an enemy.

   Can somebody recommend which one will best suit my needs? I wrote a home grown CGRectContains for the melee weapons since that seemed simple. But multiple moving bullets and explosions might prove difficult.

   Thanks.

   Posted 2 years ago #
2. 

   ob1
   Member

   I used an homegrown one. I am interested to see what is the best solution though.

   Posted 2 years ago #
3. 

   coolman
   Member

   I use Chipmunk, expect in dealing properly with the collision callback all ok.

   Don't know nothign related Box2d,ç

   More opinnions please.

   Posted 2 years ago #
4. 

   vutronic
   Member

   I use Chipmunk too but the problem with chipmunk is you don't want to remove chipmunk objects from space inside a chipmunk's collision callback function. Your app will crash. You have to wait for the next step to do this. In the current game I'm working on, I have objects falling down and I'm temporarily removing these objects from Chipmunk's space when they hit the ground.

   Posted 2 years ago #
5. 

   shivaz
   Member

   I am also using chipmunk. With bullets there is a good tutorial about that sets up an array of reusable bullets. Then when a bullet goes off screen it is tagged as reusable, and can be used again. Makes it look like you have an endless supply of bullets.

   http://morethanmachine.com/macdev/?tag=game-demo-tutorial-series

   There is a lot of good stuff in here.

   You can modify that code , so that when a collision happens - you can change the location of the bullet to off the screen - which due to the bullet resetting code - will then reset it. So a nice way to remove it from play.

   Justin

   Posted 2 years ago #
6. 

   jd
   Member

   That's what I'm using now for bullets for now. But I'm not so sure it's the best for collision detection, when I don't take advantage of gravity or velocity movements. I'm just using MoveTo for enemies and it works fine. I'm looking for lightweight collision detection.

   Posted 2 years ago #
7. 

   shivaz
   Member

   I don't use chipmunk to move the sprites - I actually move the sprites and adjust the rotation and position of the chipmunk body using an overriden SetPosition and SetRotation on the sprites.

   Justin

   Posted 2 years ago #
8. 

   imrank1
   Member

   Has anyone been able to have bullets fire at angles? I posted a question on this on the old forum a question regarding having bullets like the one in the example on http://morethanmachine.com/macdev/?tag=game-demo-tutorial-series-.

   I have a soldier on the screen in portrait mode ( bottom of screen ). Whenever you click somewhere on the screen he rotates and points his gun in that direction. At the same time he fires a bullet. I need to rotate the bullet body in the same angle that the and then apply a velocity vector in the direction taking into account the x and y values. ( So when he rotates 45 degrees to the right the bullet fires in that 45 degree angle as well ). I tried using cpBodyApplyImpulse using x and y components calculated using basic trigonometry but it's not working correctly. The angle rotation but the bullets do not move in the right direction. Have any of you done anything like this or know of a existing example?

   Thanks

   Posted 2 years ago #
9. 

   jd
   Member

   Here you go.
   In your bullet loop:
   [b fireFromTo:weaponImage.position.x y:weaponImage.position.y a:(-weaponAngle* (M_PI/180))];

   In Bullet.m:
   

   -(void) fireFromTo: (float) x y:(float)y a:(float)a
   {
   	bulletBody->p = cpv(x,y);
   	bulletBody->v = cpv(cos(a)*480, sin(a)*320);
   }

   In Bullet.h:
   -(void) fireFromTo: (float) x y:(float)y a:(float)a;

   Posted 2 years ago #
10. 

    imrank1
    Member

    Thanks for the info on that JD.

    It's still now working for me. I added the code you mentioned but the bullets go in different directions. Somtimes shooting in the opposite direction. Maybe my trig that I'm doing is wrong? Here's my ccTouchesBegan code. The x1 and y1 variables are the x,y coordinates of the soldier on the screen.

    '- (BOOL)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
    {

    UITouch *touch = [touches anyObject];
    CGPoint point = [touch locationInView: [touch view]];

    point = [[Director sharedDirector] convertCoordinate: point];
    NSLog(@"Clicked x=%f y=%f", point.x, point.y);
    //x1 and y1 represent the place where the soldier is on the screen
    double x1 = 150 ;
    double y1 = 50;
    double y2 = point.y;
    double x2 = point.x;

    double soldierAngle ;
    if ( y2 < 50 && x2 <150)
    {
    //prevent from rotating past -90 degrees
    soldierAngle = -90;

    }
    else if ( y2 < 50 && x2 >150)
    {
    // prevent from rotating past 90 degrees
    soldierAngle = 90;

    }
    else if ( x2 < 150 )
    {
    //if user touched greater than 150
    soldierAngle=atan ( (x1 - x2)/(y1-y2) ) * 180/PI ;
    }
    else if ( x2 > 150 )
    {
    //if user touched less than 180
    soldierAngle = atan ( (x2-x1)/(y2-y1)) * 180/PI;

    }

    NSLog ( @"Soldier Angle is %f", soldierAngle ) ;

    [soldier runAction:[RotateTo actionWithDuration:0.0
    angle:soldierAngle]];

    for(Bullet *b in bullets)
    {
    if([b ready])
    {

    [b fireFromTo:soldier.position.x y:soldier.position.y a:(CC_DEGREES_TO_RADIANS(-soldierAngle))];
    [b setReady: NO];
    break;
    }
    }

    return kEventHandled;
    }'

    Posted 2 years ago #
11. 

    imrank1
    Member

    ugh...sorry i meant is still NOT working for me. The soldier is at the bottom of the screen so if he clicks below y->50 based on his x position i only rotate him a max of 90 degrees in one direction.

    Thanks for the help.

    Posted 2 years ago #
12. 

    pabloruiz55
    Member

    Hi! a little late but...
    I am using chipmunk for my game, and it does it job pretty well for me.
    But i think box2d has more things like more joint types for example...

    I would like to switch for box2d in my game, but it is almost done and i don't want to break anything :P

    These days i am going to try box2d since i reduced the hours i work at my day job so i could study for my incoming exams, but now the university is closed because of the swine flu :(
    Now have a lot of time... :D

    Posted 2 years ago #
13. 

    Greg
    Member

    When I try to change the angle of my projectile (an arrow based off of the aforementioned tutorial) I can't seem to get it to work. I've tried even just hardcoding different radian values into the cpBodySetAngle method and nothing seems to have an effect. I've also tried modifying the rotation variable, but I don't think that's the right thing to do either.

    Anyone have an idea on what I might be doing wrong? I'm trying to fire projectiles at various angles based on a two points, one being the shooter and the other being the coordinate tapped by the user. I calculate the length of the adjacent and the opposite sides and then run them through the arctangent function (atan) to determine the radians. Then I flip the radians to get the other angle (Pi/2 - radians). Then I put that radians value into the cpBodySetAngle of my arrow cpBody and fire it.
    
- (void) fireFrom:(cpVect)from to:(cpVect)to {
float radians = atan((to.x - from.x) / (to.y - from.y));
shape->body->p = from;
shape->body->v = cpv(500, 0);
cpBodySetAngle(shape->body, ((M_PI / 2) - radians));
}

    Any ideas? Much appreciated!

    Posted 2 years ago #

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