硬件遮挡查询 - gpugems2.chap6

先放下代码，未完待续。

 TraversalStack.Push(hierarchy.Root);

 while ( not TraversalStack.Empty() or not QueryQueue.Empty() ) {   
    //--PART 1: process finished occlusion queries   
    while (not QueryQueue.Empty() and [ResultAvailable(QueryQueue.Front()) or TraversalStack.Empty()] ) {    
        node = QueryQueue.Dequeue();     
        // wait if result not available    
        visiblePixels = GetOcclusionQueryResult(node);   
        if (visiblePixels > VisibilityThreshold) {     
            PullUpVisibility(node);       
            TraverseNode(node); 
        }  
    }    
    //--PART 2: hierarchical traversal    
    if ( not TraversalStack.Empty() )  {    
        node = TraversalStack.Pop();    
        if ( InsideViewFrustum(node) ) {      
            // identify previously visible nodes      
            wasVisible = node.visible and (node.lastVisited == frameID - 1);      
            // identify nodes that we cannot skip queries for       
            leafOrWasInvisible = not wasVisible or IsLeaf(node);     
            // reset node's visibility classification    
            node.visible = false;   
            // update node's visited flag   
            node.lastVisited = frameID;  
            // skip testing previously visible interior nodes  
            if ( leafOrWasInvisible ) {      
                IssueOcclusionQuery(node);     
                QueryQueue.Enqueue(node);    
            }        
            // always traverse a node if it was visible      
            if ( wasVisible ) TraverseNode(node);      
        }    
    }  
}  

TraverseNode(node) {   
    if ( IsLeaf(node) ) Render(node);   
    else TraversalStack.PushChildren(node);  
}    

PullUpVisibility(node) {    
    while (not node.visible) {     
        node.visible = true;    
        node = node.parent;    
    }  
}