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/*************************************************************************
* Copyright (C) 2008 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 */
static dmnsn_array *dmnsn_sphere_intersections_fn(const dmnsn_object *sphere,
dmnsn_line line);
static int dmnsn_sphere_inside_fn(const dmnsn_object *sphere,
dmnsn_vector point);
dmnsn_object *
dmnsn_new_sphere()
{
dmnsn_object *sphere = dmnsn_new_object();
if (sphere) {
sphere->intersections_fn = &dmnsn_sphere_intersections_fn;
sphere->inside_fn = &dmnsn_sphere_inside_fn;
}
return sphere;
}
void
dmnsn_delete_sphere(dmnsn_object *sphere)
{
dmnsn_delete_object(sphere);
}
static dmnsn_array *
dmnsn_sphere_intersections_fn(const dmnsn_object *sphere, dmnsn_line line)
{
double a, b, c, t[2];
dmnsn_array *array = dmnsn_new_array(sizeof(double));
/* Solve (x0 + nx*t)^2 + (y0 + ny*t)^2 + (z0 + nz*t)^2 == 1 */
a = line.n.x*line.n.x + line.n.y*line.n.y + line.n.z*line.n.z;
b = 2.0*(line.n.x*line.x0.x + line.n.y*line.x0.y + line.n.z*line.x0.z);
c = line.x0.x*line.x0.x + line.x0.y*line.x0.y + line.x0.z*line.x0.z - 1.0;
if (b*b - 4.0*a*c >= 0) {
t[0] = (-b + sqrt(b*b - 4.0*a*c))/(2*a);
t[1] = (-b - sqrt(b*b - 4.0*a*c))/(2*a);
dmnsn_array_set(array, 0, &t[0]);
dmnsn_array_set(array, 1, &t[1]);
}
return array;
}
static int
dmnsn_sphere_inside_fn(const dmnsn_object *sphere, dmnsn_vector point)
{
return sqrt(point.x*point.x + point.y*point.y + point.z*point.z) < 1.0;
}
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