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1 /*
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2 Simple introductory ray tracer
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3 Copyright (C) 2012 John Tsiombikas <nuclear@member.fsf.org>
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4
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5 This program is free software: you can redistribute it and/or modify
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6 it under the terms of the GNU General Public License as published by
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7 the Free Software Foundation, either version 3 of the License, or
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8 (at your option) any later version.
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9
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10 This program is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 You should have received a copy of the GNU General Public License
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16 along with this program. If not, see <http://www.gnu.org/licenses/>.
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17 */
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18 #include <stdio.h>
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19 #include "sphere.h"
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20
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21 Sphere::Sphere()
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22 {
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23 radius = 1.0;
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24 }
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25
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26 Sphere::Sphere(const Vector3 &pos, float rad)
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27 {
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28 radius = rad;
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29 this->pos = pos;
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30 }
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31
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32 bool Sphere::intersect(const Ray &inray, HitPoint *pt) const
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33 {
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34 Ray ray = inray.transformed(inv_xform);
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35
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36 float a = dot_product(ray.dir, ray.dir);
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37 float b = 2.0 * ray.dir.x * (ray.origin.x - pos.x) +
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38 2.0 * ray.dir.y * (ray.origin.y - pos.y) +
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39 2.0 * ray.dir.z * (ray.origin.z - pos.z);
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40 float c = dot_product(ray.origin, ray.origin) + dot_product(pos, pos) -
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41 2.0 * dot_product(ray.origin, pos) - radius * radius;
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42
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43 float discr = b * b - 4.0 * a * c;
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44 if(discr < 1e-4)
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45 return false;
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46
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47 float sqrt_discr = sqrt(discr);
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48 float t0 = (-b + sqrt_discr) / (2.0 * a);
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49 float t1 = (-b - sqrt_discr) / (2.0 * a);
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50
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51 if(t0 < 1e-4)
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52 t0 = t1;
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53 if(t1 < 1e-4)
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54 t1 = t0;
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55
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56 float t = t0 < t1 ? t0 : t1;
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57 if(t < 1e-4)
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58 return false;
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59
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60 // fill the HitPoint structure
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61 pt->obj = this;
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62 pt->dist = t;
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63 pt->pos = ray.origin + ray.dir * t;
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64 pt->normal = (pt->pos - pos) / radius;
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65
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66 pt->pos.transform(xform);
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67 pt->normal.transform(dir_xform);
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68 return true;
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69 }
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