/*
 * CS5600 University of Utah
 * Charles McGarvey
 * mcgarvey@eng.utah.edu
 */

#ifndef _TRIANGLE_HH_
#define _TRIANGLE_HH_

#include "element.hh"


namespace rt {


/*
 * A class for a triangle object.
 */
class triangle : public element
{
    vec_t   a;
    vec_t   b;
    vec_t   c;

public:

    triangle(vec_t a, vec_t b, vec_t c) :
        a(a), b(b), c(c)
    {}

    virtual ~triangle()
    {}

    virtual bool intersect(ray_t ray, contact_t& hit) const
    {
        plane p = plane(a, b, c);
        if (!p.intersect(ray, hit)) {
            return false;
        }

        scal_t bc[3];
        if (!barycentric(bc, hit.p)) {
            return false;
        }

#if QUIRKS
        if (vec_dot(p.normal(), hit.n) < S(0.0)) {
            hit.n = vec_neg(hit.n);
        }
#endif

        return true;
    }

    /*
     * Calculate barycentric coordinates for the triangle.
     */
    bool barycentric(scal_t* bc, vec_t v) const
    {
        scal_t denom = (b.y - c.y) * (a.x - c.x) + (c.x - b.x) * (a.y - c.y);
        bc[0] = ((b.y - c.y) * (v.x - c.x) + (c.x - b.x) * (v.y - c.y)) / denom;
        bc[1] = ((c.y - a.y) * (v.x - c.x) + (a.x - c.x) * (v.y - c.y)) / denom;
        bc[2] = S(1.0) - bc[0] - bc[1];
        if (S(0.0) <= bc[0] && bc[0] <= S(1.0) &&
            S(0.0) <= bc[1] && bc[1] <= S(1.0) &&
            S(0.0) <= bc[2] && bc[2] <= S(1.0)) {
            return true;
        }
        return false;
    }

    virtual vec_t txcoord(vec_t point) const
    {
        vec_t t1 = vec_new(S(0.0), S(0.0), S(0.0));
        vec_t t2 = vec_new(S(1.0), S(0.0), S(0.0));
        vec_t t3 = vec_new(S(1.0), S(1.0), S(0.0));
        scal_t bc[3];
        barycentric(bc, point);
        return vec_interp(t1, t2, t3, bc);
    }
};


/*
 * Destroy a new'd triangle, releasing its memory.
 */
INLINE_MAYBE
void triangle_destroy(plane* t)
{
    delete t;
}


} // namespace rt

#endif // _PLANE_HH_