source: trunk/VUT/GtpVisibilityPreprocessor/src/Polygon3.cpp @ 301

#include "Polygon3.h"
#include "Mesh.h"
#include "ViewCellBsp.h" // TODO: erase this
#include "Intersectable.h"
#include "AxisAlignedBox3.h"

// tolerance value for side relation
#define SIDE_TOLERANCE 0.002f // TODO: Test different values
#define SIDE_TOLERANCE_SQRD 0.000004f
#define AREA_LIMIT 0.0001f

Polygon3::Polygon3(): mMaterial(NULL), mParent(NULL)
{}

Polygon3::Polygon3(const VertexContainer &vertices): mVertices(vertices), mMaterial(NULL), mParent(NULL)
{}

Polygon3::Polygon3(Intersectable *parent): mMaterial(NULL), mParent(parent)
{
}
Polygon3::Polygon3(Face *face, Mesh *parentMesh)
{       
        VertexIndexContainer::iterator it = face->mVertexIndices.begin();
        for (; it != face->mVertexIndices.end();  ++it)
        {
                mVertices.push_back(parentMesh->mVertices[*it]);
                mMaterial = parentMesh->mMaterial;
        }
}

Plane3 Polygon3::GetSupportingPlane() const
{
        Vector3 v1 = mVertices[0] - mVertices[1];
        Vector3 v2 = mVertices[2] - mVertices[1];
#ifdef _DEBUG
        Debug << "plane spanned by " <<  v1 << ", " << v2  << endl;
#endif
        return Plane3(mVertices[0], mVertices[1], mVertices[2]);
}

void Polygon3::Split(Plane3 *partition, Polygon3 *front, Polygon3 *back)
{
        Vector3 ptA = mVertices.back();
        
        int sideA = partition->Side(ptA, SIDE_TOLERANCE);
        
        VertexContainer::const_iterator it;
        bool foundSplit = false;

        Vector3 prevSplitPt(ptA);

        // find line - plane intersections
        for (it = mVertices.begin(); it != mVertices.end(); ++ it)
        {
                Vector3 ptB = *it;
                int sideB = partition->Side(ptB, SIDE_TOLERANCE);
        
                // vertices on different sides => split
            if (sideB > 0)
                {
                        if (sideA < 0)
                        {
                                //-- plane - line intersection
                                Vector3 splitPt = partition->FindIntersection(ptA, ptB);
                        
                                if (!foundSplit || (SqrDistance(splitPt, prevSplitPt) > SIDE_TOLERANCE_SQRD))
                                {
                                        // add vertex to both polygons
                                        front->mVertices.push_back(splitPt);
                                        back->mVertices.push_back(splitPt);

                                        foundSplit = true;
                                        prevSplitPt = splitPt;
                                }
                        }
                        front->mVertices.push_back(ptB);
                }
                else if (sideB < 0)
                {
                        if (sideA > 0)
                        {
                                //-- plane - line intersection
                                Vector3 splitPt = partition->FindIntersection(ptA, ptB);
                        
                                if (!foundSplit || (SqrDistance(splitPt, prevSplitPt) > SIDE_TOLERANCE_SQRD))
                                {
                                        // add vertex to both polygons
                                        front->mVertices.push_back(splitPt);
                                        back->mVertices.push_back(splitPt);

                                        foundSplit = true;
                                        prevSplitPt = splitPt;
                                }       
                        }
                        back->mVertices.push_back(ptB);
                }
                else
                {
                        // vertex on plane => add vertex to both polygons
                        front->mVertices.push_back(ptB);
                        back->mVertices.push_back(ptB); 
                }
        
                ptA = ptB;
                sideA = sideB;
        }
}

float Polygon3::GetArea() const
{
        VertexContainer vtx;

        //-- rotate polygon to lie in xy plane
        Vector3 v1 = mVertices[0] - mVertices[1];
        Vector3 v2 = mVertices[2] - mVertices[1];
        Vector3 n = Normalize(CrossProd(v2,v1));

        Matrix4x4 rot = GenRotation(v1, v2, n);

        VertexContainer::const_iterator it, it_end = mVertices.end();

        for (it = mVertices.begin(); it != it_end; ++it)
                vtx.push_back(rot * (*it));

        //-- compute area
        Vector3 last = vtx.back();

        float area = 0.0f;
        for (it = vtx.begin(); it != vtx.end(); ++it)
        {
                area += last.y * (*it).x - last.x * (*it).y;

                last = *it;
        }
        //Debug << "area: " << area * 0.5 << endl;
        return area * 0.5f;
}

int Polygon3::Side(const Plane3 &plane) const
{
        int classification = ClassifyPlane(plane);
        
        if (classification == BACK_SIDE)
                return -1;
        else if (classification == FRONT_SIDE)
                return 1;

        return 0;
}

int Polygon3::ClassifyPlane(const Plane3 &plane) const
{
        VertexContainer::const_iterator it;

        bool onFrontSide = false;
        bool onBackSide = false;
        
        int count = 0;
        // find possible line-plane intersections
        for (it = mVertices.begin(); it != mVertices.end(); ++ it)
        {
                int side = plane.Side(*it, SIDE_TOLERANCE);
                
                if (side > 0)
                        onFrontSide = true;
                else if (side < 0)
                        onBackSide = true;
                
                //TODO: check if split goes through vertex
                if (onFrontSide && onBackSide) // split 
                {
                        return SPLIT;
                }
                // 3 vertices enough to decide coincident
                else if (((++ count) >= 3) && !onFrontSide && !onBackSide) 
                        return COINCIDENT; 
        }

        if (onBackSide)
        {
                return BACK_SIDE;
        }
        else if (onFrontSide)
        {
                return FRONT_SIDE;
        }

        return COINCIDENT; // plane and polygon are coincident
}


Vector3
Polygon3::Center() const
{
        int i;
        Vector3 sum = mVertices[0];
        for (i=1; i < mVertices.size(); i++)
                sum += mVertices[i];
        
        return sum/(float)i;
}


void
Polygon3::Scale(const float scale)
{
        int i;
        Vector3 center = Center();
        for (i=0; i < mVertices.size(); i++) {
                mVertices[i] = center + scale*(mVertices[i] - center);
        }
}

bool Polygon3::Valid() const
{
        if (mVertices.size() < 3)
                return false;

#if 1
        // check if area exceeds certain size
        if (AREA_LIMIT > GetArea())
        {
                //Debug << "area too small: " << GetArea() << endl;
                return false;
        }
#else
        Vector3 vtx = mVertices.back();
        VertexContainer::const_iterator it, it_end = mVertices.end();

        for (it = mVertices.begin(); it != it_end; ++it)
        {
                if (!(SqrDistance(vtx, *it) > SIDE_TOLERANCE_SQRD))
                {
                        Debug << "Malformed vertices:\n" << *this << endl;
                        return false;
                }
                vtx = *it;
        }
#endif  
        return true;
}

void Polygon3::IncludeInBox(const PolygonContainer &polys, AxisAlignedBox3 &box)
{
        PolygonContainer::const_iterator it, it_end = polys.end();

        for (it = polys.begin(); it != it_end; ++ it)
                box.Include(*(*it));
}