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/*************************************************************************
* Copyright (C) 2009-2014 Tavian Barnes <tavianator@tavianator.com> *
* *
* This file is part of The Dimension Library. *
* *
* The Dimension Library is free software; you can redistribute it and/ *
* or modify it under the terms of the GNU Lesser General Public License *
* as published by the Free Software Foundation; either version 3 of the *
* License, or (at your option) any later version. *
* *
* The Dimension Library is distributed in the hope that it will be *
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
/**
* @file
* Triangles.
*/
#include "dimension.h"
typedef struct dmnsn_triangle_payload {
dmnsn_vector a, ab, ac, na, nab, nac, normal;
} dmnsn_triangle_payload;
/** Triangle intersection callback. */
static bool
dmnsn_triangle_intersection_fn(const dmnsn_object *triangle, dmnsn_line l,
dmnsn_intersection *intersection)
{
const dmnsn_triangle_payload *payload = triangle->ptr;
double den = -dmnsn_vector_dot(l.n, payload->normal);
dmnsn_vector ax0 = dmnsn_vector_sub(l.x0, payload->a);
double t = dmnsn_vector_dot(ax0, payload->normal)/den;
double u = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(ax0, payload->ac))/den;
double v = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(payload->ab, ax0))/den;
if (t >= 0.0 && u >= 0.0 && v >= 0.0 && u + v <= 1.0) {
intersection->t = t;
intersection->normal = dmnsn_vector_add(
payload->na,
dmnsn_vector_add(
dmnsn_vector_mul(u, payload->nab),
dmnsn_vector_mul(v, payload->nac)
)
);
return true;
}
return false;
}
/** Triangle inside callback. */
static bool
dmnsn_triangle_inside_fn(const dmnsn_object *triangle, dmnsn_vector point)
{
return false;
}
/* Allocate a new triangle */
dmnsn_object *
dmnsn_new_triangle(dmnsn_vector a, dmnsn_vector b, dmnsn_vector c,
dmnsn_vector na, dmnsn_vector nb, dmnsn_vector nc)
{
na = dmnsn_vector_normalized(na);
nb = dmnsn_vector_normalized(nb);
nc = dmnsn_vector_normalized(nc);
dmnsn_triangle_payload *payload = DMNSN_MALLOC(dmnsn_triangle_payload);
payload->a = a;
payload->na = na;
payload->ab = dmnsn_vector_sub(b, a);
payload->nab = dmnsn_vector_sub(nb, na);
payload->ac = dmnsn_vector_sub(c, a);
payload->nac = dmnsn_vector_sub(nc, na);
payload->normal = dmnsn_vector_cross(payload->ab, payload->ac);
dmnsn_object *triangle = dmnsn_new_object();
triangle->ptr = payload;
triangle->intersection_fn = dmnsn_triangle_intersection_fn;
triangle->inside_fn = dmnsn_triangle_inside_fn;
triangle->free_fn = dmnsn_free;
triangle->bounding_box.min = dmnsn_vector_min(dmnsn_vector_min(a, b), c);
triangle->bounding_box.max = dmnsn_vector_max(dmnsn_vector_max(a, b), c);
return triangle;
}
/* Allocate a new flat triangle */
dmnsn_object *
dmnsn_new_flat_triangle(dmnsn_vector a, dmnsn_vector b, dmnsn_vector c)
{
/* Flat triangles are just smooth triangles with identical normals at all
verticies */
dmnsn_vector normal = dmnsn_vector_cross(
dmnsn_vector_sub(b, a),
dmnsn_vector_sub(c, a)
);
return dmnsn_new_triangle(a, b, c, normal, normal, normal);
}
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