source: trunk/VUT/GtpVisibilityPreprocessor/src/Polygon3.cpp @ 264

#include "Polygon3.h"
#include "Mesh.h"

#define SIDE_TOLERANCE 0.002f // TODO: Test different values

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

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

Polygon3::Polygon3(Face *face, Mesh *parent)
{       
        VertexIndexContainer::iterator it = face->mVertexIndices.begin();
        for (; it != face->mVertexIndices.end();  ++it)
        {
                mVertices.push_back(parent->mVertices[*it]);
                mMaterial = parent->mMaterial;
                
                //Debug << parent->mVertices[*it] << endl;
        }
}

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, int &splits)
{
        splits = 0;
        Vector3 ptA = mVertices[mVertices.size() - 1];
        
        int sideA = partition->Side(ptA, SIDE_TOLERANCE);
        
        VertexContainer::const_iterator it;

        // 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);
                        
                                // add vertex to both polygons
                                front->mVertices.push_back(splitPt);
                                back->mVertices.push_back(splitPt);
                        
                                ++ splits;
                        }
                        front->mVertices.push_back(ptB);
                }
                else if (sideB < 0)
                {
                        if (sideA > 0)
                        {
                                //-- plane - line intersection
                                Vector3 splitPt = partition->FindIntersection(ptA, ptB);
                        
                                // add vertex to both polygons
                                front->mVertices.push_back(splitPt);
                                back->mVertices.push_back(splitPt);

                                ++ splits;
                        }
                        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;
        }
}

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;

        // 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;
                }
        }

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

        // plane and polygon are coincident
        return COINCIDENT;
}


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