在Octree场景下的多层次node包围盒问题

     这两天遇到了一个问题(毕竟接触ogre不久,可能问题比较弱智哈),由于我把模型用OSMLoader的演示方法导入,它具体是通过一个场景(.osm文件)导入后,将其中的子模型分别用一个node保存,如果你提供了一个node(暂订叫rootNode),那么所有的子模型node都会添加rootNode下.

    这样本来也很没有问题,毕竟如果我用.osm导入一个大场景,为了处理碰撞,我肯定要把各个子模型分散到不同的node下,但是在Octree场景下,问题就来了,请看ogre源代码:

//same as SceneNode, only it doesn't care about children...
void OctreeNode::_updateBounds( void )
{
    mWorldAABB.setNull();
    mLocalAABB.setNull();

    // Update bounds from own attached objects
    ObjectMap::iterator i = mObjectsByName.begin();
    AxisAlignedBox bx;

    while ( i != mObjectsByName.end() )
    {

        // Get local bounds of object
        bx = i->second ->getBoundingBox();

        mLocalAABB.merge( bx );

        mWorldAABB.merge( i->second ->getWorldBoundingBox(true) );
        ++i;
    }

    //update the OctreeSceneManager that things might have moved.
    // if it hasn't been added to the octree, add it, and if has moved
    // enough to leave it's current node, we'll update it.
    if ( ! mWorldAABB.isNull() )
    {
        static_cast < OctreeSceneManager * > ( mCreator ) -> _updateOctreeNode( this );
    }

}
    不需要看代码内容,光那句注释"same as SceneNode, only it doesn't care about children...",就差点让我崩溃了,我提供的rootNode竟然无法利用子node来更新包围盒!!虽然我知道ogre的设计者肯定有他们的用意,但是这样就决定了我的rootNode无法通过_getWorldAABB来取得它的大小了(因为不考虑update时只看有没有movableObj而不看有没有子node).

 

我的解决方案:

    说来很简单,ogre不帮我算我自己算,代码如下:

  AxisAlignedBox OSE_GameFrameListener::CalculateNodeBounds( String nodeName ){

 

      SceneNode *node = mSceneMgr->getSceneNode( nodeName );

      if( node->numChildren() == 0 )

          return node->_getWorldAABB();

      AxisAlignedBox tBox;
      tBox.setNull();
      for( int cIndex = 0; cIndex < node->numChildren(); ++cIndex ){
  
            SceneNode *tmp = ( SceneNode* )( node->getChild( cIndex ) );
            tBox.merge( tmp->_getWorldAABB() );

      }

    由于利用rootNode不可能有movableObj所以,我就不去理会,如果需要考虑,可以将在返回前,遍历一次Object,并merge他们的保卫盒.

 

enjoy!!
  
      return tBox;

 }