cocos2d 设置可见区域

coco2d 设置可见区域

参考http://blog.csdn.net/tangaowen/article/details/7539536

原理

1 重写 visit  方法

2 glScissor  函数

 

-(void) visit
{
    // quick return if not visible. children won't be drawn.
    if (!visible_)
        return;
    
    kmGLPushMatrix();
    
    if ( grid_ && grid_.active)
        [grid_ beforeDraw];
    
    [self beforeDraw];//绘制前
    
    [self transform];
    
    if(children_) {
        
        [self sortAllChildren];
        
        ccArray *arrayData = children_->data;
        NSUInteger i = 0;
        
        // draw children zOrder < 0
        for( ; i < arrayData->num; i++ ) {
            CCNode *child = arrayData->arr[i];
            if ( [child zOrder] < 0 )
                [child visit];
            else
                break;
        }
        
        // self draw
        [self draw];
        
        // draw children zOrder >= 0
        for( ; i < arrayData->num; i++ ) {
            CCNode *child =  arrayData->arr[i];
            [child visit];
        }
        
    } else
        [self draw];
    
    [self  afterDraw];//绘制完成后
    
    // reset for next frame
    orderOfArrival_ = 0;
    
    if ( grid_ && grid_.active)
        [grid_ afterDraw:self];

    kmGLPopMatrix();
}
/**
 * clip this view so that outside of the visible bounds can be hidden.
 */
-(void)beforeDraw
{
    CGSize m_viewSize;
    m_viewSize.width = 300;
    m_viewSize.height = 200;
    
    glEnable(GL_SCISSOR_TEST);
    const CGFloat s = [[CCDirector sharedDirector] contentScaleFactor];
    glScissor(self.position.x *s - m_viewSize.width*s *0.5f,
              self.position.y * s - m_viewSize.height*s *0.5f,
              m_viewSize.width*s,
              m_viewSize.height*s);
      
}
/**
 * retract what's done in beforeDraw so that there's no side effect to
 * other nodes.
 */
-(void)afterDraw
{
    glDisable(GL_SCISSOR_TEST);
}