source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/CHCTraverser.cpp @ 2818

#include "CHCTraverser.h"
#include "SceneEntity.h"


namespace CHCDemoEngine
{

CHCTraverser::CHCTraverser() 
{}


OcclusionQuery *CHCTraverser::IssueOcclusionQueryWithGeometry(BvhNode *node)
{
        // render out what is left in the qeue
        if (mUseRenderQueue) ApplyRenderQueue();

        OcclusionQuery *query = mQueryHandler.RequestQuery();
        query->AddNode(node);

        ++ mStats.mNumIssuedQueries;

        query->BeginQuery();

        RenderNode(node);
        if (mUseRenderQueue) ApplyRenderQueue();

        query->EndQuery();

        return query;
}


void CHCTraverser::Traverse()
{
        //-- PART 1: process finished occlusion queries
        while (!mDistanceQueue.empty() || !mQueryQueue.empty())
        {
                while (!mQueryQueue.empty() && 
                           (mQueryQueue.front()->ResultAvailable() || mDistanceQueue.empty()))
                {
                        OcclusionQuery *query = mQueryQueue.front();
                        mQueryQueue.pop();
                        
                        // wait until result available
                        int visiblePixels = query->GetQueryResult();

                        if (visiblePixels > mVisibilityThreshold)
                        {
                                BvhNode *node = query->GetFrontNode();
                                node->SetAssumedVisibleFrameId(mFrameId + mAssumedVisibleFrames);

                                node->SetVisible(true);
                                mBvh->MakeParentsVisible(node);
                                TraverseNode(node);
                        }
                        else
                        {
                                
                                ++ mStats.mNumQueryCulledNodes;
                        }
                }       

                //-- PART 2: hierarchical traversal
                if (!mDistanceQueue.empty())
                {
                        BvhNode *node = mDistanceQueue.top();
                        mDistanceQueue.pop();
        
                        if (mBvh->IsWithinViewFrustum(node))
                        {
                                // for near plane intersecting bounding box possible 
                                // wrong results => skip occlusion query
                                if (IntersectsNearPlane(node))
                                {
                                        // update node's visited flag
                                        node->SetLastVisitedFrame(mFrameId);
                                        node->SetVisible(true);
                                        mBvh->MakeParentsVisible(node);

                                        TraverseNode(node);
                                }
                                else
                                {               
                                        // identify previously visible nodes
                                        const bool wasVisible = node->IsVisible() && (node->GetLastVisitedFrame() == mFrameId - 1);
                                        
                                        // identify nodes that we cannot skip queries for
                                        const bool queryFeasible = (!wasVisible || 
                                                (node->IsVirtualLeaf() && (node->GetAssumedVisibleFrameId() <= mFrameId)));

                                        // update node's visited flag
                                        node->SetLastVisitedFrame(mFrameId);
                                        
                                        // skip testing previously visible interior nodes
                                        if (queryFeasible)
                                        {
                                                OcclusionQuery *query;

                                                // if this node is a previous visible leaf:
                                                // leaves will be rendered anyway => we can directly query the real geometry 
                                                if (wasVisible && mUseOptimization)
                                                        query = IssueOcclusionQueryWithGeometry(node);
                                                else
                                                        query = IssueOcclusionQuery(node);

                                                mQueryQueue.push(query);
                                        }
                                        else
                                        {
                                                if (node->IsVirtualLeaf())
                                                {
                                                        node->SetVisible(true);
                                                        mBvh->MakeParentsVisible(node);
                                                } 
                                                else // reset visibility classification
                                                {
                                                        node->SetVisible(false);
                                                }
                                        }

                                        // always traverse a node if it was visible
                                        if (wasVisible)
                                                TraverseNode(node);
                                }
                        }
                        else
                        {
                                // for stats
                                ++ mStats.mNumFrustumCulledNodes;
                        }
                }
        }
}

}