source: GTP/trunk/Lib/Vis/Preprocessing/src/Polygon3.cpp @ 863

#include "Polygon3.h"
#include "Mesh.h"
#include "AxisAlignedBox3.h"
#include "Ray.h"
#include "Triangle3.h"


namespace GtpVisibilityPreprocessor {


Polygon3::Polygon3(): 
mMaterial(NULL), mParent(NULL), mPiercingRays(0)
{
        // mostly there will be triangles
        //mVertices.reserve(3);
}

Polygon3::Polygon3(const VertexContainer &vertices): 
mMaterial(NULL), mParent(NULL), mPiercingRays(0)
{
        mVertices.reserve(vertices.size());
        mVertices = vertices;
}


Polygon3::Polygon3(MeshInstance *parent): 
mMaterial(NULL), mParent(parent), mPiercingRays(0)
{}


Polygon3::Polygon3(Face *face, Mesh *parentMesh):
mMaterial(NULL), mParent(NULL), mPiercingRays(0)
{       
        mVertices.reserve(face->mVertexIndices.size());
        
        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
{
        return Plane3(mVertices[0], mVertices[1], mVertices[2]);
}


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

void Polygon3::Split(const Plane3 &partition, 
                                         Polygon3 &front, 
                                         Polygon3 &back,
                                         const float epsilon)
{
        Vector3 ptA = mVertices.back();
        
        int sideA = partition.Side(ptA, epsilon);
        
        VertexContainer::const_iterator it;
        
        Vector3 lastSplit;

        bool foundSplit = false;

        //-- find line - plane intersections
        for (it = mVertices.begin(); it != mVertices.end(); ++ it)
        {
                Vector3 ptB = *it;
                int sideB = partition.Side(ptB, epsilon);
        
                // 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 (!foundSplit || (!EpsilonEqualV3(splitPt, lastSplit, epsilon)))
                                {
                                        // add vertex to both polygons
                                        front.mVertices.push_back(splitPt);
                                        back.mVertices.push_back(splitPt);
                                        
                                        lastSplit = splitPt;
                                        foundSplit = true;
                                }
                        }
                        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 (!foundSplit || (!EpsilonEqualV3(splitPt, lastSplit, epsilon)))
                                {
                                        // add vertex to both polygons
                                        front.mVertices.push_back(splitPt);
                                        back.mVertices.push_back(splitPt);

                                        lastSplit = splitPt;
                                        foundSplit = true;
                                }       
                        }
                        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]);
    
    return 0.5f * fabs(DotProd(GetNormal(), v));
}


int Polygon3::Side(const Plane3 &plane, 
                                   const float epsilon) const
{
        int classification = ClassifyPlane(plane, epsilon);
        
        if (classification == BACK_SIDE)
                return -1;
        else if (classification == FRONT_SIDE)
                return 1;
        // plane splits polygon
        return 0;
}


int Polygon3::ClassifyPlane(const Plane3 &plane, 
                                                        const float epsilon) const
{
        VertexContainer::const_iterator it, it_end = mVertices.end();

        bool onFrontSide = false;
        bool onBackSide = false;
        
        int count = 0;
        // find possible line-plane intersections
        for (it = mVertices.begin(); it != it_end; ++ it)
        {
                const int side = plane.Side(*it, epsilon);
                
                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 float epsilon) const
{
        if (mVertices.size() < 3)
                return false;

        //TODO: remove for performance
#if 0
        if (1)
        {
                // check if area exceeds certain size
                if (GetArea() < AREA_LIMIT)
                {
                        Debug << "area too small: " << GetArea() << endl;
                        return false;
                }
        }
        
        if (1)
        {
                Vector3 vtx = mVertices.back();
                VertexContainer::const_iterator it, it_end = mVertices.end();

                for (it = mVertices.begin(); it != it_end; ++it)
                {
                        if (EpsilonEqualV3(vtx, *it, 0.0001))
                        {
                                //Debug << "Malformed vertices:\n" << *this << endl;
                                return false;
                        }
                        vtx = *it;
                }
        }
#endif

        return true;
}


// 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;
}


void Polygon3::InheritRays(Polygon3 &front_piece, 
                                               Polygon3 &back_piece) const
{
        if (mPiercingRays.empty())
                return;

        RayContainer::const_iterator it, 
                it_end = mPiercingRays.end();

        for (it = mPiercingRays.begin(); it != it_end; ++ it)
        {
                switch((*it)->GetId())
                {
                case Ray::BACK:
                        back_piece.mPiercingRays.push_back(*it);
                        break;
                case Ray::FRONT:
                        front_piece.mPiercingRays.push_back(*it);
                        break;
                case Ray::FRONT_BACK:
                        back_piece.mPiercingRays.push_back(*it);
                        break;
                case Ray::BACK_FRONT:
                        front_piece.mPiercingRays.push_back(*it);
                        break;
                default:
                        break;
                }
        }
}


int Polygon3::ClassifyPlane(const PolygonContainer &polys, 
                                                        const Plane3 &plane,
                                                        const float epsilon)
{
        bool onFrontSide = false;
        bool onBackSide = false;
        PolygonContainer::const_iterator it;

        // find intersections
        for (it = polys.begin(); it != polys.end(); ++ it)
        {
        const int cf = (*it)->ClassifyPlane(plane, epsilon);
                
        if (cf == FRONT_SIDE)
                        onFrontSide = true;
                else if (cf == BACK_SIDE)
                        onBackSide = true;
                
                if ((cf == SPLIT) || (cf == COINCIDENT) || (onFrontSide && onBackSide))
                {
                        return SPLIT;
                }
        }

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


int Polygon3::ParentObjectsSize(const PolygonContainer &polys)
{
        int count = 0;

        PolygonContainer::const_iterator it, it_end = polys.end();

        MeshInstance::NewMail();

        for (it = polys.begin(); it != it_end; ++ it)
        {
                if ((*it)->mParent && !(*it)->mParent->Mailed())
                {
                        ++ count;
                        (*it)->mParent->Mail();
                }
        }
        return count;
}


float Polygon3::GetArea(const PolygonContainer &cell)
{
        float area = 0;
        PolygonContainer::const_iterator pit;

        for (pit = cell.begin(); pit != cell.end(); ++ pit)
        {
                area += (*pit)->GetArea();
        }

        return area;
}


Polygon3 *Polygon3::CreateReversePolygon() const
{
        Polygon3 *revPoly = new Polygon3();

        VertexContainer::const_reverse_iterator rit, 
                        rit_end = mVertices.rend();

        for(rit = mVertices.rbegin(); rit != rit_end; ++ rit)
                revPoly->mVertices.push_back(*rit);

        return revPoly;
}


void Polygon3::Triangulate(vector<Triangle3> &triangles) const
{
        int i = 1;
        int j = 0;
        int k = (int)mVertices.size() - 1;
        int count = 0;

        while (i < k)
        {
                triangles.push_back(Triangle3(mVertices[i], mVertices[j], mVertices[k]));

                if ((count ++) % 2)
                        j = i ++;
                else
                        j = k --;
        }
}


void Polygon3::Triangulate(VertexIndexContainer &indices) const
{
        int i = 1;
        int j = 0;
        int k = (int)mVertices.size() - 1;

        int count = 0;

        while (i < k)
        {
                indices.push_back(k);
                indices.push_back(j);
                indices.push_back(i);

                if ((count ++) % 2)
                        j = i ++;
                else
                        j = k --;
        }
}


void IncludePolyInMesh(const Polygon3 &poly, Mesh &mesh)
{
        const int n = (int)mesh.mVertices.size();

    //-- add the vertices
    VertexContainer::const_iterator vit, vit_end = poly.mVertices.end();
        for (vit = poly.mVertices.begin(); vit != vit_end; ++ vit)
        {
                mesh.mVertices.push_back(*vit);
        }

        // one quad => no triangulation necessary
        if (poly.mVertices.size() == 4)
        {
                mesh.AddFace(new Face(n, n + 1, n + 2, n + 3));
                return;
        }
        
        VertexIndexContainer indices;
        poly.Triangulate(indices);

        // add indices of triangle strip
        for (int i = 0; i < (int)indices.size(); i += 3)
        {
                Face *face = new Face(n + indices[i], 
                                                          n + indices[i + 1], 
                                                          n + indices[i + 2]);
                mesh.AddFace(face);
        }
}

}