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

#include "HierarchyNode.h"
#include "glInterface.h"
#include <math.h>
#include <limits.h>
#include <float.h>

typedef vector<Geometry *> GeometryList;

// criteria and values partly taken from Piringer's thesis

// values used as termination criteria for the tree generation
// the overall surface
float HierarchyNode::sSurfaceThreshold;
// the maximum tree depth
int HierarchyNode::sMaxDepth;
// maximum number of objects in a node
int HierarchyNode::sGeometryThreshold;

// percentage of allowed deviation from the center split plane
float HierarchyNode::sSplitBandwith;

// also render bounding volume
bool HierarchyNode::sRenderBoundingVolume = false;

HierarchyNode::HierarchyNode(): mVisible(false), mLastVisited(0), 
mParent(NULL), mOcclusionQuery(0), mAABValid(false), mLeftChild(NULL), mRightChild(NULL),
mNumHierarchyNodes(1), mSplitAxis(X_AXIS), mLastRendered(-1), mSplitValue(0),
mDepth(0), mEnclosedSpaceValid(false), mDistance(0)
{
        copyVector3Values(mBoundingBox.min, 0, 0, 0);
        copyVector3Values(mBoundingBox.max, 0, 0, 0);

        copyVector3Values(mEnclosedSpace.min, 0, 0, 0);
        copyVector3Values(mEnclosedSpace.max, 0, 0, 0);

        // bounding box color
        mBoxColor[0] = mBoxColor[2] = 0; mBoxColor[1] = 1.0;
}

HierarchyNode::HierarchyNode(const Vector3 boundLower, const Vector3 boundUpper, 
                                                         HierarchyNode *parent, int depth)
:mNumHierarchyNodes(1), mOcclusionQuery(0), mLeftChild(NULL), 
mRightChild(NULL), mSplitAxis(X_AXIS), mVisible(false), 
mLastVisited(0), mParent(parent), mAABValid(false), 
mLastRendered(-1), mSplitValue(0), mDepth(depth), 
mEnclosedSpaceValid(true), mDistance(0)
{
        copyVector3Values(mBoundingBox.min, 0, 0, 0);
        copyVector3Values(mBoundingBox.max, 0, 0, 0);

        copyVector3(mEnclosedSpace.min, boundLower);
        copyVector3(mEnclosedSpace.max, boundUpper);

        float vol = calcAABoxSurface(mEnclosedSpace);

        mBoxColor[0] = mBoxColor[2] = 0; mBoxColor[1] = 1.0;
}


void HierarchyNode::InitKdTree(HierarchyNode *root)
{
        sMaxDepth = (int)((log((float) root->GetGeometry().size())/log(2.0f)) * 20.0f);

        sSurfaceThreshold = FLT_MAX;

        // factor times mininal surface as determination criterium
        const float factor = 2.5;

        for (GeometryList::const_iterator it = root->GetGeometry().begin(); it != root->GetGeometry().end(); it++)
        {
                // same geometry can possible be in to or more nodes => also test for them
                float surface = calcAABoxSurface((*it)->GetBoundingVolume()) * factor;

                if(surface < sSurfaceThreshold) sSurfaceThreshold = surface;
        }

        // number of objects in a leaf
        sGeometryThreshold = 1;

        // percentage of allowed deviation from the center split plane
        sSplitBandwith = 0.15;
}


HierarchyNode::~HierarchyNode()
{
        if(mLeftChild)
                delete mLeftChild;

        if(mRightChild)
                delete mRightChild;
}

int HierarchyNode::Render()
{
        int renderedGeometry = 0;

        if(sRenderBoundingVolume)
        {
                glColor3fv(mBoxColor);
        RenderBoundingVolumeForVisualization();
        }

        // prevent the geometry to be rendered several times in the same frame
        if(mLastRendered != mLastVisited)
        {
                for (GeometryList::const_iterator it = mGeometry.begin(); it != mGeometry.end(); it++)
                {
                        // same geometry can possible be in to or more nodes => also test for them
                        if((*it)->GetLastVisited() != mLastVisited)
                        {
                                (*it)->SetLastVisited(mLastVisited);
                                (*it)->Render();
                                renderedGeometry ++;
                        }
                }
                mLastRendered = mLastVisited;
        }

        return renderedGeometry;
}

bool HierarchyNode::Visible()
{
        return mVisible;
}

void HierarchyNode::SetVisible(bool visible)
{
        mVisible = visible;
}

void HierarchyNode::SetLeftChild(HierarchyNode *child)
{
        mLeftChild = child;
}

void HierarchyNode::SetRightChild(HierarchyNode *child)
{
        mRightChild = child;
}

HierarchyNode *HierarchyNode::GetLeftChild()
{
        return mLeftChild;
}

HierarchyNode *HierarchyNode::GetRightChild()
{
        return mRightChild;
}

int HierarchyNode::LastVisited()
{
        return mLastVisited;
}

void HierarchyNode::SetLastVisited(int lastVisited)
{
        mLastVisited = lastVisited;
}

bool HierarchyNode::IsLeaf()
{
        return (!mLeftChild && !mRightChild);
}

void HierarchyNode::AddGeometry(Geometry *geometry)
{
        mGeometry.push_back(geometry);
                
        if(!mAABValid)
        {
                copyVector3(mBoundingBox.min, geometry->GetBoundingVolume().min);
                copyVector3(mBoundingBox.max, geometry->GetBoundingVolume().max);

                mAABValid = true;
        }
        else
                combineAABoxes(&mBoundingBox, geometry->GetBoundingVolume());

        // root node
        if(mDepth == 0)
        {
                if(!mEnclosedSpaceValid)
                {
                        copyVector3(mEnclosedSpace.min, geometry->GetBoundingVolume().min);
                        copyVector3(mEnclosedSpace.max, geometry->GetBoundingVolume().max);

                        mEnclosedSpaceValid = true;
                }
                else 
                        combineAABoxes(&mEnclosedSpace, geometry->GetBoundingVolume()); 
        }
        else
        {
                // cut boxes so they fit into the enclosed space
                clipAABoxByAABox(&mBoundingBox, mEnclosedSpace);
        }
}

HierarchyNode *HierarchyNode::GetParent()
{
        return mParent;
}

int HierarchyNode::GetOcclusionQuery()
{
        return mOcclusionQuery;
}

void HierarchyNode::SetOcclusionQuery(int occlusionQuery)
{
        mOcclusionQuery = occlusionQuery;
}

void HierarchyNode::RenderBoundingVolume()
{
        Vector3x8 vertices;

        calcAABoxPoints(vertices, mBoundingBox);

        //glPolygonMode(GL_FRONT, GL_LINE);
        //     7+------+6
        //     /|     /|
        //    / |    / |
        //   / 4+---/--+5
        // 3+------+2 /    y   z
        //  | /    | /     |  /
        //  |/     |/      |/
        // 0+------+1      *---x

        //---- render AABB
        glBegin(GL_TRIANGLE_FAN);
                glVertex3dv(vertices[6]);
                glVertex3dv(vertices[5]);
                glVertex3dv(vertices[4]);
                glVertex3dv(vertices[7]);
                glVertex3dv(vertices[3]);
                glVertex3dv(vertices[2]);
                glVertex3dv(vertices[1]);
                glVertex3dv(vertices[5]);
        glEnd();

        //---- render second half of AABB
        glBegin(GL_TRIANGLE_FAN);
                glVertex3dv(vertices[0]);
                glVertex3dv(vertices[1]);
                glVertex3dv(vertices[2]);
                glVertex3dv(vertices[3]);
                glVertex3dv(vertices[7]);
                glVertex3dv(vertices[4]);
                glVertex3dv(vertices[5]);
                glVertex3dv(vertices[1]);
        glEnd();
}


void HierarchyNode::RenderBoundingVolumeForVisualization()
{
        glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
        glDisable(GL_LIGHTING);
        glDisable(GL_CULL_FACE);
                
        RenderBoundingVolume();

        glEnable(GL_CULL_FACE);
        glEnable(GL_LIGHTING);
        glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
}



const AABox &HierarchyNode::GetBoundingVolume()
{
        return mBoundingBox;
}

int     HierarchyNode::GenerateKdTree()
{
        // check the termination criterium (a heuristic)
        if (SimpleEnough()) 
        {
                return 1;
        }

        // largest dimension will be split
        Vector3 size;
        diffVector3(size, mBoundingBox.max, mBoundingBox.min);
    
        if (size[X_AXIS] > size[Y_AXIS])        
                mSplitAxis      = (size[X_AXIS] > size[Z_AXIS]) ? X_AXIS : Z_AXIS;
        else                                    
                mSplitAxis      = (size[Y_AXIS] > size[Z_AXIS]) ? Y_AXIS : Z_AXIS;

        // select the value of the split plane
        mSplitValue = ComputeSplitPlane();
        
        // generate the children
        Vector3 changedLower;
        Vector3 changedUpper;

        copyVector3(changedLower, mEnclosedSpace.min);
        copyVector3(changedUpper, mEnclosedSpace.max);
                
        changedLower[mSplitAxis] = mSplitValue;
        changedUpper[mSplitAxis] = mSplitValue;

        mLeftChild      = new HierarchyNode(mEnclosedSpace.min, changedUpper, this, mDepth + 1);
        mRightChild     = new HierarchyNode(changedLower, mEnclosedSpace.max, this, mDepth + 1);

        // add the geometry to the according children
        for (GeometryList::iterator it = mGeometry.begin(); it != mGeometry.end(); it++)
        {
                if ((*it)->GetBoundingVolume().min[mSplitAxis] >= mSplitValue)
                {
                        // box lies completely within right part
                        mRightChild->AddGeometry(*it);
                }
                else if ((*it)->GetBoundingVolume().max[mSplitAxis] <= mSplitValue)
                {
                        // box lies completely within left part
                        mLeftChild->AddGeometry((*it));
                }
                else
                {
                        //---- box intersects both parts
                        mLeftChild->AddGeometry((*it));
                        mRightChild->AddGeometry((*it));
                }
        }

        //---- we continue with the children
        int leftSize  = mLeftChild->GenerateKdTree();
        int rightSize = mRightChild->GenerateKdTree();

        // since the geometry is now referenced by the children
        mGeometry.clear();
        
        mNumHierarchyNodes = leftSize + rightSize + 1;

        return mNumHierarchyNodes;
}

bool HierarchyNode::SimpleEnough()
{
        return ((mGeometry.size() <= (unsigned int)sGeometryThreshold) ||
                    (calcAABoxSurface(mBoundingBox) <= sSurfaceThreshold) ||
                        (sMaxDepth <= mDepth));
}

float HierarchyNode::ComputeSplitPlane()
{
        float left      = mBoundingBox.min[mSplitAxis];
        float right     = mBoundingBox.max[mSplitAxis];

        // the smaller the value returned from the heuristic, the better => big starting value
        float bestValue = FLT_MAX; 
        float result = 0.0f;

        bool found      = false;

        // calculate the borders of the band
        float currLeft, currRight;
        currLeft = currRight = (left + right) / 2.0f;
        
        currLeft  -= (right - left) * sSplitBandwith;
        currRight += (right - left) * sSplitBandwith;

        // check all geometry within that node
        for (GeometryList::const_iterator it = mGeometry.begin(); it != mGeometry.end(); it++)
        {
                // one border of the geometry's AABB
                float leftPlane  = (*it)->GetBoundingVolume().min[mSplitAxis];
                // the other border of the geometry's AABB
                float rightPlane = (*it)->GetBoundingVolume().max[mSplitAxis];
                
                // only consider planes that lie within the band
                if ((leftPlane > currLeft) && (leftPlane < currRight))
                {
                        // compute the heuristic for the left plane and note the value if it was good
                        float currValue = ComputeHeuristics(leftPlane);

                        if (currValue < bestValue)
                        {
                                bestValue = currValue;
                                result    = leftPlane;
                                found     = true;
                        }
                }

                if ((rightPlane > currLeft) && (rightPlane < currRight))
                {
                        // compute the heuristic for the right plane and note the value if it was good
                        float currValue = ComputeHeuristics(rightPlane);

                        if (currValue < bestValue)
                        {
                                bestValue       = currValue;
                                result          = rightPlane;
                                found           = true;
                        }
                }
        }

        // in case we haven't found any proper plane, we simply take the center
        if (!found)     
                result = (left + right) / 2.0f;
                        
        return result;
}

float HierarchyNode::ComputeHeuristics(float pos)
{
        // this implements a very simple heuristic: it simply counts the nodes being intersected by the splitplane
        float result = 0.0f;

        for (GeometryList::const_iterator it = mGeometry.begin(); it != mGeometry.end(); it++)
        {
                if (((*it)->GetBoundingVolume().min[mSplitAxis] < pos) &&
                        ((*it)->GetBoundingVolume().max[mSplitAxis] > pos))
                {
                        result += 1.0f;
                }
        }

        return result;
}

int HierarchyNode::GetNumHierarchyNodes()
{
        return mNumHierarchyNodes;
}

void HierarchyNode::PushChildrenOrdered(const Vector3 viewpoint, TraversalStack &traversalStack)
{
        if(viewpoint[mSplitAxis] > mSplitValue)
        {
                traversalStack.push(mLeftChild);
                traversalStack.push(mRightChild);
        }
        else
        {
                traversalStack.push(mRightChild);
                traversalStack.push(mLeftChild);
        }
}


void HierarchyNode::SetRenderBoundingVolume(bool renderBoundingVolume)
{
        sRenderBoundingVolume = renderBoundingVolume;
}


GeometryList &HierarchyNode::GetGeometry()
{
        return mGeometry;
}


float HierarchyNode::GetDistance()
{
        return mDistance;
}


void HierarchyNode::SetDistance(float distance)
{
        mDistance = distance;
}