summaryrefslogtreecommitdiffstats
path: root/libdimension/triangle.c
blob: 8e584d8d7aac25c66fa02e339d8d9862d074b392 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
/*************************************************************************
 * 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"

/** Triangle type. */
typedef struct {
  dmnsn_object object;
  dmnsn_vector na, nab, nac;
} dmnsn_triangle;

/** Triangle intersection callback. */
static bool
dmnsn_triangle_intersection_fn(const dmnsn_object *object, dmnsn_line l,
                               dmnsn_intersection *intersection)
{
  const dmnsn_triangle *triangle = (const dmnsn_triangle *)object;

  /* See the change of basis in dmnsn_new_triangle() */
  double t = -l.x0.z/l.n.z;
  double u = l.x0.x + t*l.n.x;
  double v = l.x0.y + t*l.n.y;
  if (t >= 0.0 && u >= 0.0 && v >= 0.0 && u + v <= 1.0) {
    intersection->t      = t;
    intersection->normal = dmnsn_vector_add(
      triangle->na,
      dmnsn_vector_add(
        dmnsn_vector_mul(u, triangle->nab),
        dmnsn_vector_mul(v, triangle->nac)
      )
    );
    return true;
  }

  return false;
}

/** Triangle inside callback. */
static bool
dmnsn_triangle_inside_fn(const dmnsn_object *triangle, dmnsn_vector point)
{
  return false;
}

dmnsn_object *
dmnsn_new_triangle(dmnsn_pool *pool, dmnsn_vector vertices[3])
{
  dmnsn_vector normal = dmnsn_vector_cross(
    dmnsn_vector_sub(vertices[1], vertices[0]),
    dmnsn_vector_sub(vertices[2], vertices[0])
  );
  dmnsn_vector normals[] = { normal, normal, normal };
  return dmnsn_new_smooth_triangle(pool, vertices, normals);
}

/* Allocate a new triangle */
dmnsn_object *
dmnsn_new_smooth_triangle(dmnsn_pool *pool, dmnsn_vector vertices[3], dmnsn_vector normals[3])
{
  dmnsn_vector na = dmnsn_vector_normalized(normals[0]);
  dmnsn_vector nb = dmnsn_vector_normalized(normals[1]);
  dmnsn_vector nc = dmnsn_vector_normalized(normals[2]);

  dmnsn_triangle *triangle = DMNSN_PALLOC(pool, dmnsn_triangle);
  triangle->na  = na;
  triangle->nab = dmnsn_vector_sub(nb, na);
  triangle->nac = dmnsn_vector_sub(nc, na);

  dmnsn_object *object = &triangle->object;
  dmnsn_init_object(pool, object);
  object->intersection_fn = dmnsn_triangle_intersection_fn;
  object->inside_fn = dmnsn_triangle_inside_fn;
  object->bounding_box.min = dmnsn_zero;
  object->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 0.0);

  /*
   * Make a change-of-basis matrix
   *
   * The new vector space has corners at <0, 1, 0>, <0, 0, 1>, and 0,
   * corresponding to the basis (ab, ac, ab X ac).
   */
  dmnsn_vector ab = dmnsn_vector_sub(vertices[1], vertices[0]);
  dmnsn_vector ac = dmnsn_vector_sub(vertices[2], vertices[0]);
  dmnsn_vector normal = dmnsn_vector_cross(ab, ac);
  object->intrinsic_trans = dmnsn_new_matrix4(ab, ac, normal, vertices[0]);

  return object;
}