Question

I am working on a game and I would like to add a proper slicing feature in it.. so when a sprite sliced, 2 new sprites should be created.. please check here

At the moment, I am just reducing the size and duplicating the sprites.. Something like this.. Thanks in advance..

 - (BOOL) sliceSprite: (Sprite *) sprite withPath: (UIBezierPath *) slicePath


 {

            CGSize size = sprite.size;
            size.width /= 2; 
            size.height /=2;
            sprite.size = size;
            sprite.sliced = YES;

            Sprite *newSprite = [[Sprite alloc] initWithImage: sprite.image];

            newSprite.position = sprite.position;
            newSprite.size = size;
            newSprite.sliced = YES;
            newSprite.inView = YES;
            newSprite.xVelocity = SLICE_SPEEDUP * sprite.yVelocity;
            newSprite.yVelocity = SLICE_SPEEDUP * sprite.xVelocity;
            newSprite.angularVelocity = -SLICE_REVUP * sprite.angularVelocity;

            [sprites addObject: newSprite];
            [newSprite release];

        sprite.angularVelocity = SLICE_REVUP * sprite.angularVelocity;
            sprite.xVelocity = -SLICE_SPEEDUP * sprite.xVelocity;
            sprite.yVelocity = -SLICE_SPEEDUP * sprite.yVelocity;

            return YES;
    }

- (void) sliceSpritesInSwipePath
{
    CGRect swipeRect = [swipePath bounds];


        for (NSUInteger i = 0; i < [sprites count]; i++)
        {
                Sprite *sprite = [sprites objectAtIndex: i];

                if ([sprite intersectsWithPathInArray: swipePoints
                                               inRect: swipeRect])
                        if ([self sliceSprite: sprite withPath: swipePath])
                        {

                                [self resetSwipe];

                                if (![sliceSound isPlaying])
                                        [sliceSound play];

                break;
                        }
        }

}

Answer 1

Since you’re using CoreGraphics here, why not simply use a clipping path when drawing the sprite(s)?

Duplicate the sprite to be sliced, then apply simple polygons masking the two halves as their respective clipping paths. The function you need is called CGContextClip and a short tutorial can be found here.

Edit: The tutorial lists this example:

CGContextBeginPath (context);
CGContextAddArc (context, w/2, h/2, ((w>h) ? h : w)/2, 0, 2*PI, 0);
CGContextClosePath (context);
CGContextClip (context);

This sets the current path to a circle, then applies the current path as the clipping region.