原地址：http://ityran.com/thread-118-1-1.html
写一个CCDirector（Extension）这样的Category
在头文件中加入：
@interface CCDirector(Extension)
/**Pops scene with transitions
*/
- (void) popSceneWithTransition: (Class)c duration:(ccTime)t;
@end
在实现文件中加入：
-(void) popSceneWithTransition: (Class)transitionClass duration:(ccTime)t;
{
NSAssert( runningScene_ != nil, @"A running Scene is needed");
[scenesStack_ removeLastObject];
NSUInteger c = [scenesStack_ count];
if( c == 0 ) {
[self end];
} else {
CCScene* scene = [transitionClass transitionWithDuration:t scene:[scenesStack_ objectAtIndex:c-1]];
[scenesStack_ replaceObjectAtIndex:c-1 withObject:scene];
nextScene_ = scene;
}
}