Implement triangles.

4 files changed, 128 insertions, 1 deletions

diff --git a/libdimension/Makefile.am b/libdimension/Makefile.am
index 0f3dee5..b042fc9 100644
--- a/libdimension/Makefile.am
+++ b/libdimension/Makefile.am
@@ -111,7 +111,8 @@ libdimension_la_SOURCES = $(nobase_include_HEADERS)                            \
                           threads.c                                            \
                           threads.h                                            \
                           timer.c                                              \
-                          torus.c
+                          torus.c                                              \
+                          triangle.c
 libdimension_la_CFLAGS  = $(AM_CFLAGS)
 libdimension_la_LDFLAGS = -version-info 0:0:0 -no-undefined $(AM_LDFLAGS)
 libdimension_la_LIBADD  = -lm -lpthread
diff --git a/libdimension/dimension/objects.h b/libdimension/dimension/objects.h
index aa53329..ba9547d 100644
--- a/libdimension/dimension/objects.h
+++ b/libdimension/dimension/objects.h
@@ -26,6 +26,16 @@
 #include <stdbool.h>
 
 /**
+ * A triangle.
+ * @param[in] a  The first corner of the triangle.
+ * @param[in] b  The second corner of the triangle.
+ * @param[in] c  The third corner of the triangle.
+ */
+dmnsn_object *dmnsn_new_triangle(dmnsn_vector a,
+                                 dmnsn_vector b,
+                                 dmnsn_vector c);
+
+/**
  * A plane.
  * @param[in] normal  The normal vector of the plane.
  * @return A plane through the origin, with the given normal.
diff --git a/libdimension/tests/render.c b/libdimension/tests/render.c
index 04897d6..a9d20d7 100644
--- a/libdimension/tests/render.c
+++ b/libdimension/tests/render.c
@@ -190,6 +190,39 @@ dmnsn_new_test_scene(void)
   );
   dmnsn_array_push(scene->objects, &spike);
 
+  /* Triangle strip */
+
+  dmnsn_array *strip_array = dmnsn_new_array(sizeof(dmnsn_object *));
+  dmnsn_vector a = dmnsn_zero;
+  dmnsn_vector b = dmnsn_new_vector(0.0, sqrt(3.0)/2.0, 0.5);
+  dmnsn_vector c = dmnsn_z;
+  dmnsn_texture *strip_textures[3] = {
+    dmnsn_new_texture(),
+    dmnsn_new_texture(),
+    dmnsn_new_texture(),
+  };
+  strip_textures[0]->pigment = dmnsn_new_solid_pigment(dmnsn_red);
+  strip_textures[1]->pigment = dmnsn_new_solid_pigment(dmnsn_orange);
+  strip_textures[2]->pigment = dmnsn_new_solid_pigment(dmnsn_yellow);
+  for (unsigned int i = 0; i < 128; ++i) {
+    dmnsn_object *triangle = dmnsn_new_triangle(a, b, c);
+    triangle->texture = strip_textures[i%3];
+    DMNSN_INCREF(triangle->texture);
+    dmnsn_array_push(strip_array, &triangle);
+
+    a = b;
+    b = c;
+    c = dmnsn_vector_add(a, dmnsn_z);
+  }
+  for (unsigned int i = 0; i < 3; ++i) {
+    dmnsn_delete_texture(strip_textures[i]);
+  }
+
+  dmnsn_object *strip = dmnsn_new_csg_union(strip_array);
+  dmnsn_delete_array(strip_array);
+  strip->trans = dmnsn_translation_matrix(dmnsn_new_vector(5.0, -2.0, -4.0));
+  dmnsn_array_push(scene->objects, &strip);
+
   dmnsn_object *plane = dmnsn_new_plane(dmnsn_new_vector(0.0, 1.0, 0.0));
   plane->trans = dmnsn_translation_matrix(dmnsn_new_vector(0.0, -2.0, 0.0));
   dmnsn_pattern *checker1 = dmnsn_new_checker_pattern();
diff --git a/libdimension/triangle.c b/libdimension/triangle.c
new file mode 100644
index 0000000..bd54e1a
--- /dev/null
+++ b/libdimension/triangle.c
@@ -0,0 +1,83 @@
+/*************************************************************************
+ * Copyright (C) 2009-2010 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, 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->ray      = l;
+    intersection->t        = t;
+    intersection->normal   = payload->normal;
+    intersection->texture  = triangle->texture;
+    intersection->interior = triangle->interior;
+    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_object *triangle = dmnsn_new_object();
+
+  dmnsn_triangle_payload *payload =
+    dmnsn_malloc(sizeof(dmnsn_triangle_payload));
+  payload->a      = a;
+  payload->ab     = dmnsn_vector_sub(b, a);
+  payload->ac     = dmnsn_vector_sub(c, a);
+  payload->normal = dmnsn_vector_cross(payload->ab, payload->ac);
+
+  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;
+}