source: GTP/trunk/Lib/Vis/Preprocessing/src/Triangle3.cpp @ 2542

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


using namespace std;

namespace GtpVisibilityPreprocessor {

        
Triangle3::Triangle3(const Vector3 &a, const Vector3 &b, const Vector3 &c) 
{
        Init(a, b, c);
}


void Triangle3::Init(const Vector3 &a, const Vector3 &b, const Vector3 &c) 
{
        mVertices[0] = a;
        mVertices[1] = b;
        mVertices[2] = c;
}


float Triangle3::GetSpatialAngle(const Vector3 &point) const
{
        return 0.0f;
}


int
Triangle3::CastRay(const Ray &ray,
                                   float &t,
                                   const float nearestT,
                                   Vector3 &normal) const
{
        //////////////
        // specialised triangle ray casting version
        // using ray-plane intersection
        
        // get triangle edge vectors and plane normal
        const Vector3 u = mVertices[0] - mVertices[1];
    const Vector3 v = mVertices[2] - mVertices[1];

        // cross product
    normal = Normalize(CrossProd(v, u));

        // ray direction vector
    const Vector3 dir = ray.GetDir();
    const Vector3 w0 = ray.GetLoc() - mVertices[1];

        // params to calc ray-plane intersect
    const float a = -DotProd(normal, w0);
    const float b = DotProd(normal, dir);

        // check for division by zero
        if (fabs(b) < Limits::Small) 
        {   
                // ray is parallel to triangle plane
        if (a == 0)
                {
                        // ray lies in triangle plane
            return Ray::INTERSECTION_OUT_OF_LIMITS;
                }
        else
                {
                        // ray disjoint from plane
                        return Ray::NO_INTERSECTION;
                }
    }

    // distance from origin of ray to plane
    t = a / b;

    if (t <= Limits::Small) // ray goes away from triangle
        {
          return Ray::INTERSECTION_OUT_OF_LIMITS;
        }
        // already found nearer intersection
        else if ((ray.GetType() == Ray::LOCAL_RAY) && (t >= nearestT))
        {
                return Ray::NO_INTERSECTION;
        }

        /////////////////
    //-- found intersection point
        //-- check if it is inside triangle
  
        const Vector3 pt = ray.GetLoc() + t * dir; 
#if GTP_DEBUG
        if (!pt.CheckValidity())
        {
                cout << "tr: " << *this << endl;
                cout << "v: " << pt << " t: " << t << " a: " << a << " b: " << b << " n: " << normal << endl;
        }
#endif
        const Vector3 w = pt - mVertices[1];

        const float uu = DotProd(u, u);
    const float uv = DotProd(u, v);
    const float vv = DotProd(v, v);
    
        const float wu = DotProd(w, u);
    const float wv = DotProd(w, v);


        const float D = uv * uv - uu * vv;

    // get and test parametric coords
    const float s = (uv * wv - vv * wu) / D;

    if ((s < -Limits::Small) || (s > 1.0f + Limits::Small)) // pt is outside triangle
        {       
        return Ray::NO_INTERSECTION;
        }

        const float s2 = (uv * wu - uu * wv) / D;

    if ((s2 < -Limits::Small) || ((s + s2) > 1.0f + Limits::Small)) // pt is outside triangle
        {       
        return Ray::NO_INTERSECTION;
        }

        return Ray::INTERSECTION; // I is in T
}


AxisAlignedBox3 Triangle3::GetBoundingBox() const
{
        AxisAlignedBox3 box;
        box.Initialize();

        box.Include(mVertices[0]);
        box.Include(mVertices[1]);
        box.Include(mVertices[2]);

        return box;
}


Vector3 Triangle3::GetNormal() const 
{
        const Vector3 v1 = mVertices[0] - mVertices[1];
        const Vector3 v2 = mVertices[2] - mVertices[1];

        return Normalize(CrossProd(v2, v1));
}


Vector3 Triangle3::GetCenter() const 
{
        return (mVertices[0] + mVertices[1] + mVertices[2]) / 3.0f;
}


float Triangle3::GetArea() const 
{
        Vector3 v1 = mVertices[0] - mVertices[1], v2=mVertices[2] - mVertices[1];
        return 0.5f * Magnitude(CrossProd(v2, v1));
}


bool Triangle3::CheckValidity() const
{
        return !(
                EpsilonEqualV3(mVertices[0], mVertices[1]) ||
                EpsilonEqualV3(mVertices[0], mVertices[2]) ||
                EpsilonEqualV3(mVertices[1], mVertices[2])
                );
}


bool Triangle3::GetPlaneIntersection(const Plane3 &plane, 
                                                                         Vector3 &intersectA, 
                                                                         Vector3 &intersectB) const
{
        int side[3];

        // compute distance from plane
        for (int i = 0; i < 3; ++ i)
        {
                side[i] = plane.Side(mVertices[i], Limits::Small);
        }

        /////
        // no intersection => early exit
        if (((side[0] > 0) && (side[1] > 0) && (side[2] > 0)) ||
                ((side[0] < 0) && (side[1] < 0) && (side[2] < 0)))
        {
                return false;
        }

        /////////////
        // at least 2 triangle vertices lie in plane => early exit

        for (int i = 0; i < 3; ++ i)
        {
                if (!side[i] && !side[(i + 1) % 3])
                {
                        intersectA = mVertices[i];
                        intersectB = mVertices[(i + 1) % 3];
                        
                        return true;
                }
        }

        bool foundA = false;

        // compute intersection points
        for (int i = 0; i < 3; ++ i)
        {
                const int i_2 = (i + 1) % 3;

                // intersection found
                if ((side[i] >= 0) && (side[i_2] <= 0) ||
                        (side[i] <= 0) && (side[i_2] >= 0))
                {       
                        const float t = plane.FindT(mVertices[i], mVertices[i_2]);
                        
                        if (!foundA)
                        {
                                intersectA = mVertices[i] + t * (mVertices[i_2] - mVertices[i]);
                        
                                foundA = true;
                        }
                        else
                        {
                                intersectB = mVertices[i] + t * (mVertices[i_2] - mVertices[i]);
                        
                                return true;
                        }
                }
        }

        cout << "warning! wrong triangle - plane intersection" << endl;
        return false; // something went wrong!
}


}