source: trunk/VUT/GtpVisibilityPreprocessor/src/Polygon3.cpp @ 317

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

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

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

Polygon3::Polygon3(MeshInstance *parent): mMaterial(NULL), mParent(parent)
{}

// creates an "infinite" polygon from this plane
//Polygon3::Polygon3(Plane3 plane)
//{}

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]);
}

Vector3 Polygon3::GetNormal() const 
{
    return Normalize(CrossProd(mVertices[0] - mVertices[1],
                                                           mVertices[2] - mVertices[1]));
}

void Polygon3::Split(const Plane3 &partition, 
                                         Polygon3 &front, 
                                         Polygon3 &back, 
                                         VertexContainer &splitPts)
{
        Vector3 ptA = mVertices.back();
        
        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);
                        
                                // test if split point not too close to previous split point
                                if ((splitPts.size() == 0) || 
                                        (SqrDistance(splitPt, splitPts.back()) > SIDE_TOLERANCE_SQRD))
                                {
                                        // add vertex to both polygons
                                        front.mVertices.push_back(splitPt);
                                        back.mVertices.push_back(splitPt);
                                        
                                        splitPts.push_back(splitPt);
                                }
                        }
                        front.mVertices.push_back(ptB);
                }
                else if (sideB < 0)
                {
                        if (sideA > 0)
                        {
                                //-- plane - line intersection
                                Vector3 splitPt = partition.FindIntersection(ptA, ptB);
                                // test if split point not too close to other split point
                                        // test if split point not too close to previous split point
                                if ((splitPts.size() == 0) || 
                                        (SqrDistance(splitPt, splitPts.back()) > SIDE_TOLERANCE_SQRD))
                                {
                                        // add vertex to both polygons
                                        front.mVertices.push_back(splitPt);
                                        back.mVertices.push_back(splitPt);

                                        splitPts.push_back(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
{
        Vector3 v = CrossProd(mVertices.back(), mVertices.front());
    
    for (int i=0; i < mVertices.size() - 1; ++i)
                v += CrossProd(mVertices[i], mVertices[i+1]);
    
    //Debug << "area2: " << 0.5f * fabs(DotProd(GetNormal(), v)) << endl;  

        return 0.5f * fabs(DotProd(GetNormal(), v));
}

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));
}

// int_lineseg returns 1 if the given line segment intersects a 2D
// ray travelling in the positive X direction.  This is used in the
// Jordan curve computation for polygon intersection.
inline int
int_lineseg(float px,
            float py,
            float u1,
            float v1,
            float u2,
            float v2)
{
        float t;
        float ydiff;

        u1 -= px; u2 -= px;       // translate line
        v1 -= py; v2 -= py;

        if ((v1 > 0 && v2 > 0) ||
                (v1 < 0 && v2 < 0) ||
                (u1 < 0 && u2 < 0))
        return 0;

        if (u1 > 0 && u2 > 0)
        return 1;

        ydiff = v2 - v1;

        if (fabs(ydiff) < Limits::Small) 
        {         // denominator near 0
                if (((fabs(v1) > Limits::Small) || (u1 > 0) || (u2 > 0)))
                        return 0;
                return 1;
        }

        t = -v1 / ydiff;                  // Compute parameter

        return (u1 + t * (u2 - u1)) > 0;
}

int Polygon3::CastRay(const Ray &ray, float &t, const float nearestT)
{
        Plane3 plane = GetSupportingPlane();
        float dot = DotProd(plane.mNormal, ray.GetDir());

        // Watch for near-zero denominator
        // ONLY single sided polygons!!!!!
        if (dot > -Limits::Small)
        //  if (fabs(dot) < Limits::Small)
        return Ray::NO_INTERSECTION;

        t = (-plane.mD - DotProd(plane.mNormal, ray.GetLoc())) / dot;

        if (t <= Limits::Small)
        return Ray::INTERSECTION_OUT_OF_LIMITS;

        if (t >= nearestT) {
        return Ray::INTERSECTION_OUT_OF_LIMITS; // no intersection was found
        }

        int count = 0;
        float u, v, u1, v1, u2, v2;
        int i;

        int paxis = plane.mNormal.DrivingAxis();

        // Project the intersection point onto the coordinate plane
        // specified by which.
        ray.Extrap(t).ExtractVerts(&u, &v, paxis);

        int size = (int)mVertices.size();

        mVertices.back().ExtractVerts(&u1, &v1, paxis );

        if (0 && size <= 4) 
        {
                // assume a convex face
                for (i = 0; i < size; i++) 
                {
                mVertices[i].ExtractVerts(&u2, &v2, paxis);
            
                        // line u1, v1, u2, v2
            
                        if ((v2 - v1)*(u1 - u) > (u2 - u1)*(v1 - v))
                                return Ray::NO_INTERSECTION;

                        u1 = u2;
                        v1 = v2;
        }

        return Ray::INTERSECTION;
        }

        // We're stuck with the Jordan curve computation.  Count number
        // of intersections between the line segments the polygon comprises
        // with a ray originating at the point of intersection and
        // travelling in the positive X direction.
        for (i = 0; i < size; i++) 
        {
                mVertices[i].ExtractVerts(&u2, &v2, paxis);

                count += (int_lineseg(u, v, u1, v1, u2, v2) != 0);

                u1 = u2;
                v1 = v2;
        }

        // We hit polygon if number of intersections is odd.
        return (count & 1) ? Ray::INTERSECTION : Ray::NO_INTERSECTION;
}