Triangle.cc

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#include "BoundingBox.h"
#include "Triangle.h"
#include "HitRecord.h"
#include "Math.h"
#include "Ray.h"
#include <iostream>
#include <stdlib.h>
using namespace std;

Triangle::Triangle(Material* material, const Point &A, const Point &B, const Point &C)
    : Primitive(material), a(A), b(B), c(C)
{
}

Triangle::~Triangle()
{
}


void Triangle::intersect(HitRecord& hit, const RenderContext& context, const Ray& ray) const
{
    Vector edge1, edge2, tvec, pvec, qvec;

    double det, inv_det, u, v, t;

    /* find vectors for two edges sharing vert0 */
    edge1 = b - a;
    edge2 = c - a;

   /* begin calculating determinant - also used to calculate U parameter */
    pvec = Cross(ray.direction(), edge2);

    /* if determinant is near zero, ray lies in plane of triangle */
    det = Dot(edge1, pvec);

   if (det > -EPSILON && det < EPSILON)
       return;

   inv_det = 1.0 / det;

   /* calculate distance from vert0 to ray origin */
   tvec = ray.origin() - a;

   /* calculate U parameter and test bounds */
   u = Dot(tvec, pvec) * inv_det;
   if (u < 0.0 || u > 1.0)
       return;

   /* prepare to test V parameter */
   qvec = Cross(tvec, edge1);

   /* calculate V parameter and test bounds */
   v = Dot(ray.direction(), qvec) * inv_det;
   if (v < 0.0 || u + v > 1.0)
       return;

   /* calculate t, ray intersects triangle */
   t = Dot(edge2, qvec) * inv_det;

   if (hit.hit(t, this, matl)) {
       // probably want to stash u and v
   }
}


void Triangle::normal(Vector& normal, const RenderContext&,
                      const Point&, const Ray&, const HitRecord&) const
{

    Vector edge1, edge2;

    edge1 = b - a;
    edge2 = c - a;

    normal = Cross(edge1, edge2);
    normal.normalize();
}


void Triangle::getBounds(BoundingBox& bbox) const
{
    bbox.extend(a);
    bbox.extend(b);
    bbox.extend(c);
}

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