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

#ifndef __TRI_H__
#define __TRI_H__

#include "mat.h"
#include "vert.h"


/*
 * A triangle is a polygon of three vertices.
 */
struct tri
{
    vert_t a;
    vert_t b;
    vert_t c;
};
typedef struct tri tri_t;

/*
 * Initialize a triangle.
 */
__fast__
void tri_init(tri_t* t, vert_t a, vert_t b, vert_t c)
{
    t->a = a;
    t->b = b;
    t->c = c;
}


/*
 * Create a new triangle.
 */
__fast__
tri_t tri_new(vert_t a, vert_t b, vert_t c)
{
    tri_t t;
    tri_init(&t, a, b, c);
    return t;
}

#define TRI_ZERO tri_new(VERT_ZERO, VERT_ZERO, VERT_ZERO)


/*
 * Create a new triangle on the heap.
 */
__fast__
tri_t* tri_alloc(vert_t a, vert_t b, vert_t c)
{
    tri_t* t = (tri_t*)mem_alloc(sizeof(tri_t));
    tri_init(t, a, b, c);
    return t;
}


/*
 * Apply a transformation matrix to alter the triangle geometry.
 */
__fast__
tri_t tri_transform(tri_t t, mat_t m)
{
    t.a.v = mat_apply(m, t.a.v);
    t.b.v = mat_apply(m, t.b.v);
    t.c.v = mat_apply(m, t.c.v);
    return t;
}


/*
 * Get the barycentric coordinates of a vector against a triangle.  The
 * returned coordinates will be a linear combination, but they may not
 * actually be barycentric coordinates.  Use the function vec_is_barycentric
 * to check if they really are barycentric coordinates, meaning the point
 * vector v is inside the triangle, ignoring the Z components.
 */
vec_t tri_barycentric(const tri_t* t, vec_t v);


#endif // __TRI_H__