source: trunk/VUT/chcdemo/RenderTraverser.cpp @ 10

#include "RenderTraverser.h"
#include "glInterface.h"
#include "Timers.h"

extern "C"
{
        #include "MathStuff.h"
}


RenderTraverser::RenderTraverser(): mFrameID(1), mVisibilityThreshold(0),
mHierarchyRoot(NULL), mOcclusionQueries(NULL), mCurrentTestIdx(0), mIsQueryMode(false),
mNumTraversedNodes(0), mNumQueryCulledNodes(0), mNumFrustumCulledNodes(0),
mRenderTime(0), mNumRenderedGeometry(0), mUseOptimization(true)
{
}

RenderTraverser::~RenderTraverser()
{
        if(mOcclusionQueries) 
                delete [] mOcclusionQueries;
}

void RenderTraverser::Render(int mode)
{
        mDistanceQueue.push(mHierarchyRoot);

        long startTime = getTime();

        Preprocess();

        switch(mode)
        {
                case RENDER_CULL_FRUSTUM:
                        RenderCullFrustum();
            break;
                case RENDER_STOP_AND_WAIT:
                        RenderStopAndWait();
                        break;
                case RENDER_COHERENT:
                        RenderCoherentWithQueue();
                        break;
                default:
                        RenderCullFrustum();
                        break;
        }

        mFrameID ++;
        ResetQueries();

        long endTime = getTime();
        mRenderTime = endTime - startTime;

        finishTiming();
}

/**
This is the standard render traversal algorithm doing only frustum culling
*/
void RenderTraverser::RenderCullFrustum()
{
        while(!mDistanceQueue.empty())
        {
                HierarchyNode *node = mDistanceQueue.top();
                mDistanceQueue.pop();
        
                // interesting for the visualization, so rest and set
                node->SetVisible(false);
                mNumTraversedNodes ++;

                bool intersects;
        
                if(InsideViewFrustum(node, intersects))
                {
                        // update node's visited flag => needed for rendering
                        // so set it also here
                        node->SetLastVisited(mFrameID);
                        node->SetVisible(true);
                        TraverseNode(node);
                }
                else
                {
                        mNumFrustumCulledNodes ++;
                }
        }
}

void RenderTraverser::RenderStopAndWait()
{
        while(! mDistanceQueue.empty())
        {
                HierarchyNode *node = mDistanceQueue.top();
                mDistanceQueue.pop();
                mNumTraversedNodes ++;
                // interesting for the visualization, so rest and set
                node->SetVisible(false);

                bool intersects;
                
                if(InsideViewFrustum(node, intersects))
                {
                        // update node's visited flag
                        node->SetLastVisited(mFrameID);

                        // for near plane intersecting abbs possible 
                        // wrong results => skip occlusion query
                        if(intersects)
                        {
                                node->SetVisible(true);
                                TraverseNode(node);
                        }
                        else
                        {
                                IssueOcclusionQuery(node, false);
                                
                                // wait if result not available
                                int visiblePixels = GetOcclusionQueryResult(node);
                                
                                // node visible
                                if(visiblePixels > mVisibilityThreshold)
                                {
                                        node->SetVisible(true);
                                        TraverseNode(node);
                                }
                                else
                                {
                                        mNumQueryCulledNodes ++;
                                }
                        }                                       
                }
                else
                {
                        mNumFrustumCulledNodes ++;
                }
        }
}

void RenderTraverser::RenderCoherentWithQueue()
{
        QueryQueue queryQueue;

        //-- PART 1: process finished occlusion queries
        while(!mDistanceQueue.empty() || !queryQueue.empty())
        {
                while(!queryQueue.empty() && 
                          (ResultAvailable(queryQueue.front()) ||       mDistanceQueue.empty()))
                {
                        HierarchyNode *node = queryQueue.front();
                        queryQueue.pop();
                        
                        // wait until result available
                        int visiblePixels = GetOcclusionQueryResult(node);

                        if(visiblePixels > mVisibilityThreshold)
                        {
                                PullUpVisibility(node);
                                TraverseNode(node);
                        }
                        else
                        {
                                mNumQueryCulledNodes ++;
                        }
                }       

                //-- PART 2: hierarchical traversal
                if(! mDistanceQueue.empty())
                {
                        HierarchyNode *node = mDistanceQueue.top();

                        mDistanceQueue.pop();
        
                        mNumTraversedNodes ++;

                        bool intersects;
                        
                        if(InsideViewFrustum(node, intersects))
                        {
                                // for near plane intersecting abbs possible 
                                // wrong results => skip occlusion query
                                if(intersects)
                                {
                                        // update node's visited flag
                                        node->SetLastVisited(mFrameID);

                                        PullUpVisibility(node);
                                        TraverseNode(node);
                                }
                                else
                                {               
                                        // identify previously visible nodes
                                        bool wasVisible = node->Visible() && (node->LastVisited() == mFrameID - 1);
                                        
                                        // identify nodes that we cannot skip queries for
                                        bool leafOrWasInvisible = !wasVisible || node->IsLeaf();

                                        // reset node's visibility classification 
                                        node->SetVisible(false);

                                        // update node's visited flag
                                        node->SetLastVisited(mFrameID);
                                
                                        // skip testing previously visible interior nodes
                                        if(leafOrWasInvisible)
                                        {
                                                IssueOcclusionQuery(node, wasVisible);
                                                queryQueue.push(node);
                                        }
                                        
                                        // always traverse a node if it was visible
                                        if(wasVisible)
                                                TraverseNode(node);
                                }
                        }
                        else
                        {
                                // for stats
                                mNumFrustumCulledNodes ++;
                        }
                }
        }
}
        
void RenderTraverser::TraverseNode(HierarchyNode *node)
{
        if(node->IsLeaf())
                mNumRenderedGeometry += node->Render();
        else 
        {
                // for non leafs this renders only the bounding volume (if the flag is set)
                //node->Render();
                mDistanceQueue.push(node->GetLeftChild());
                mDistanceQueue.push(node->GetRightChild());
        }
}

void RenderTraverser::RenderVisualization()
{
        mDistanceQueue.push(mHierarchyRoot);

        while(! mDistanceQueue.empty())
        {
                HierarchyNode *node = mDistanceQueue.top();
                mDistanceQueue.pop();

                // identify previously visible nodes
                bool wasVisible = node->Visible() && (node->LastVisited() == mFrameID - 1);

                if(wasVisible)
                        TraverseNode(node);
                else
                {
                        // also render culled nodes
                        glColor3f(1.0,0.0,0.0);
                        node->RenderBoundingVolumeForVisualization();           
                }
        }
}


void RenderTraverser::PullUpVisibility(HierarchyNode *node)
{
        while(node && !node->Visible())
        {
                node->SetVisible(true);
                node = node->GetParent();
        }
}

bool RenderTraverser::ResultAvailable(HierarchyNode *node)
{
        int result;

        glGetQueryivARB(node->GetOcclusionQuery(),
                                        GL_QUERY_RESULT_AVAILABLE_ARB, &result);

        return (result == GL_TRUE);
}

void RenderTraverser::SetHierarchy(HierarchyNode *sceneRoot)
{
        mHierarchyRoot = sceneRoot;

        // not valid anymore for new hierarchy => delete
        delete [] mOcclusionQueries;
        mOcclusionQueries = NULL;
}

HierarchyNode *RenderTraverser::GetHierarchy()
{
        return mHierarchyRoot;
}

int RenderTraverser::GetOcclusionQueryResult(HierarchyNode *node)
{
        unsigned int result;
        
        glGetQueryObjectuivARB(node->GetOcclusionQuery(), GL_QUERY_RESULT_ARB, &result);

        return (int)result;
}


void RenderTraverser::Switch2GLQueryState()
{       
        // boolean used to avoid unnecessary state changes
        if(!mIsQueryMode)
        {
                glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
                glDepthMask(GL_FALSE);
                glDisable(GL_LIGHTING);
                mIsQueryMode = true;
        }
}


void RenderTraverser::Switch2GLRenderState()
{
        // boolean used to avoid unnecessary state changes
        if(mIsQueryMode)
        {
                // switch back to rendermode            
                glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
                glDepthMask(GL_TRUE);
                glEnable(GL_LIGHTING);
                mIsQueryMode = false;
        }
}

void RenderTraverser::IssueOcclusionQuery(HierarchyNode *node, bool wasVisible)
{
        // get next available test id
        unsigned int occlusionQuery = mOcclusionQueries[mCurrentTestIdx++];
        
        node->SetOcclusionQuery(occlusionQuery);
        // do the actual occlusion query for this node
        glBeginQueryARB(GL_SAMPLES_PASSED_ARB, occlusionQuery);
        
        // if leaf and was visible => will be rendered anyway, thus we
        // can also test with the real geometry 
        if(node->IsLeaf() && wasVisible && mUseOptimization)
        {
                mNumRenderedGeometry += node->Render();
        }
        else
        {
                // change state so the bounding box gets not actually rendered on the screen
                Switch2GLQueryState();
                node->RenderBoundingVolume();
                Switch2GLRenderState();
        }

        glEndQueryARB(GL_SAMPLES_PASSED_ARB);
}

void RenderTraverser::Preprocess()
{
        if(!mOcclusionQueries)
        {
                mOcclusionQueries = new unsigned int[mHierarchyRoot->GetNumHierarchyNodes()];
        }

        // view frustum planes for view frustum culling
        calcViewFrustumPlanes(&mClipPlanes, mProjViewMatrix);
        calcAABNPVertexIndices(mNPVertexIndices, mClipPlanes);
        // generate ids for occlusion test
        glGenQueriesARB(mHierarchyRoot->GetNumHierarchyNodes(), mOcclusionQueries);
        mCurrentTestIdx = 0;

        // reset statistics
        mNumTraversedNodes = 0;
        mNumQueryCulledNodes = 0;
        mNumFrustumCulledNodes = 0;
        mNumRenderedGeometry = 0;
}


void RenderTraverser::ResetQueries()
{
        // tell the driver that the occlusion queries won't be needed any more
        glDeleteQueriesARB(mHierarchyRoot->GetNumHierarchyNodes(), mOcclusionQueries);
}


void RenderTraverser::SetViewpoint(Vector3 const &viewpoint)
{
        copyVector3(mViewpoint, viewpoint);
}
        

void RenderTraverser::SetProjViewMatrix(Matrix4x4 const &projViewMatrix)
{
        copyMatrix(mProjViewMatrix, projViewMatrix);
}


bool RenderTraverser::InsideViewFrustum(HierarchyNode *node, bool &intersects)
{
        Vector3x8 vertices;
        
        bool intersect = false;

        calcAABoxPoints(vertices, node->GetBoundingVolume());

        // simply test all 6 vertices
        for (int i = 0; i < 6; i++)
        {               
                // test the n-vertex
                // note: the calcAABNearestVertexId should be preprocessed
                if(!pointBeforePlane(mClipPlanes.plane[i], vertices[mNPVertexIndices[i * 2]]))
                {
                        // outside
                        return false;
                }
        }

        // test if bounding box is intersected by nearplane (using the p-vertex)
        intersects = (!pointBeforePlane(mClipPlanes.plane[5], vertices[mNPVertexIndices[11]]));

        // -- get vector from viewpoint to center of bounding volume
        Vector3 vec;
        calcAABoxCenter(vec, node->GetBoundingVolume());
        diffVector3(vec, vec, mViewpoint);

        // compute distance from nearest point to viewpoint
        diffVector3(vec, vertices[calcAABNearestVertexIdx(vec)], mViewpoint);
        node->SetDistance(squaredLength(vec));
        
        return true;
}


void RenderTraverser::SetVisibilityThreshold(int threshold)
{
        mVisibilityThreshold = threshold;
}

long RenderTraverser::GetRenderTime()
{
        return mRenderTime;
}

int RenderTraverser::GetNumTraversedNodes()
{
        return mNumTraversedNodes;
}

int RenderTraverser::GetNumQueryCulledNodes()
{
        return mNumQueryCulledNodes;
}

int RenderTraverser::GetNumFrustumCulledNodes()
{
        return mNumFrustumCulledNodes;
}


int RenderTraverser::GetNumRenderedGeometry()
{
        return mNumRenderedGeometry;
}


int RenderTraverser::GetVisibilityThreshold()
{
        return mVisibilityThreshold;
}

void RenderTraverser::SetUseOptimization(bool useOptimization)
{
        mUseOptimization = useOptimization;
        printf("using opt %d\n", mUseOptimization);
}