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diff --git a/libdimension/cube.c b/libdimension/cube.c
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+/*************************************************************************
+ * Copyright (C) 2009 Tavian Barnes <tavianator@gmail.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/>. *
+ *************************************************************************/
+
+#include "dimension.h"
+#include <stdlib.h> /* For malloc */
+#include <math.h> /* For sqrt */
+
+/*
+ * Cube
+ */
+
+/* Cube callbacks */
+static dmnsn_intersection *dmnsn_cube_intersection_fn(const dmnsn_object *cube,
+ dmnsn_line line);
+static int dmnsn_cube_inside_fn(const dmnsn_object *cube,
+ dmnsn_vector point);
+
+/* Allocate a new cube object */
+dmnsn_object *
+dmnsn_new_cube()
+{
+ dmnsn_object *cube = dmnsn_new_object();
+ if (cube) {
+ cube->intersection_fn = &dmnsn_cube_intersection_fn;
+ cube->inside_fn = &dmnsn_cube_inside_fn;
+ cube->min = dmnsn_new_vector(-1.0, -1.0, -1.0);
+ cube->max = dmnsn_new_vector(1.0, 1.0, 1.0);
+ }
+ return cube;
+}
+
+/* Intersections callback for a cube */
+static dmnsn_intersection *
+dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
+{
+ double t = -1.0, t_temp;
+ dmnsn_vector p, normal;
+ dmnsn_intersection *intersection = NULL;
+
+ /* Six ray-plane intersection tests (x, y, z) = +/- 1.0 */
+
+ if (line.n.x != 0.0) {
+ /* x = -1.0 */
+ t_temp = (-1.0 - line.x0.x)/line.n.x;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
+ }
+
+ /* x = 1.0 */
+ t_temp = (1.0 - line.x0.x)/line.n.x;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
+ }
+ }
+
+ if (line.n.y != 0.0) {
+ /* y = -1.0 */
+ t_temp = (-1.0 - line.x0.y)/line.n.y;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
+ }
+
+ /* y = 1.0 */
+ t_temp = (1.0 - line.x0.y)/line.n.y;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
+ }
+ }
+
+ if (line.n.z != 0.0) {
+ /* z = -1.0 */
+ t_temp = (-1.0 - line.x0.z)/line.n.z;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
+ }
+
+ /* z = 1.0 */
+ t_temp = (1.0 - line.x0.z)/line.n.z;
+ p = dmnsn_line_point(line, t_temp);
+ if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0
+ && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
+ {
+ t = t_temp;
+ normal = dmnsn_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
+ }
+ }
+
+ if (t >= 0.0) {
+ intersection = dmnsn_new_intersection();
+ intersection->ray = line;
+ intersection->t = t;
+ intersection->normal = normal;
+ intersection->texture = cube->texture;
+ }
+
+ return intersection;
+}
+
+/* Inside callback for a cube */
+static int
+dmnsn_cube_inside_fn(const dmnsn_object *cube, dmnsn_vector point)
+{
+ return point.x > -1.0 && point.x < 1.0
+ && point.y > -1.0 && point.y < 1.0
+ && point.z > -1.0 && point.z < 1.0;
+}