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


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) const
{
	// get triangle edge vectors and plane normal
	const Vector3 u = mVertices[1] - mVertices[0];
    const Vector3 v = mVertices[2] - mVertices[0];

    const Vector3 n = u * v;  // cross product

    const Vector3 dir = ray.GetDir();           // ray direction vector
    const Vector3 w0 = ray.GetLoc() - mVertices[0];

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

	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
		{
			return Ray::NO_INTERSECTION; // ray disjoint from plane
		}
    }

    // get intersect point of ray with triangle plane
    t = a / b;

    if (t < 0.0) // ray goes away from triangle
	{
        return Ray::NO_INTERSECTION; // => no intersect
	}

    // for a segment, also test if (r > 1.0) => no intersect

	// intersect point of ray and plane
    const Vector3 pt = ray.GetLoc() + t * dir; 


	///////////////////////////////////////////////
    //-- is point inside triangle?
   
	const Vector3 w = pt - mVertices[0];

	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 < 0.0 || s > 1.0) // pt is outside triangle
	{
        return Ray::NO_INTERSECTION;
	}

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

    if (s2 < 0.0 || (s + s2) > 1.0) // 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));
}


}