nuclear@3: /*
nuclear@3: Simple introductory ray tracer
nuclear@3: Copyright (C) 2012  John Tsiombikas <nuclear@member.fsf.org>
nuclear@3: 
nuclear@3: This program is free software: you can redistribute it and/or modify
nuclear@3: it under the terms of the GNU General Public License as published by
nuclear@3: the Free Software Foundation, either version 3 of the License, or
nuclear@3: (at your option) any later version.
nuclear@3: 
nuclear@3: This program is distributed in the hope that it will be useful,
nuclear@3: but WITHOUT ANY WARRANTY; without even the implied warranty of
nuclear@3: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
nuclear@3: GNU General Public License for more details.
nuclear@3: 
nuclear@3: You should have received a copy of the GNU General Public License
nuclear@3: along with this program.  If not, see <http://www.gnu.org/licenses/>.
nuclear@3: */
nuclear@0: #include <stdio.h>
nuclear@0: #include "sphere.h"
nuclear@0: 
nuclear@0: Sphere::Sphere()
nuclear@0: {
nuclear@0: 	radius = 1.0;
nuclear@0: }
nuclear@0: 
nuclear@0: Sphere::Sphere(const Vector3 &pos, float rad)
nuclear@0: {
nuclear@0: 	radius = rad;
nuclear@0: 	this->pos = pos;
nuclear@0: }
nuclear@0: 
nuclear@0: bool Sphere::intersect(const Ray &inray, HitPoint *pt) const
nuclear@0: {
nuclear@0: 	Ray ray = inray.transformed(inv_xform);
nuclear@0: 
nuclear@0: 	float a = dot_product(ray.dir, ray.dir);
nuclear@0: 	float b = 2.0 * ray.dir.x * (ray.origin.x - pos.x) +
nuclear@0: 		2.0 * ray.dir.y * (ray.origin.y - pos.y) +
nuclear@0: 		2.0 * ray.dir.z * (ray.origin.z - pos.z);
nuclear@0: 	float c = dot_product(ray.origin, ray.origin) + dot_product(pos, pos) -
nuclear@0: 		2.0 * dot_product(ray.origin, pos) - radius * radius;
nuclear@0: 
nuclear@0: 	float discr = b * b - 4.0 * a * c;
nuclear@0: 	if(discr < 1e-4)
nuclear@0: 		return false;
nuclear@0: 
nuclear@0: 	float sqrt_discr = sqrt(discr);
nuclear@0: 	float t0 = (-b + sqrt_discr) / (2.0 * a);
nuclear@0: 	float t1 = (-b - sqrt_discr) / (2.0 * a);
nuclear@0: 
nuclear@0: 	if(t0 < 1e-4)
nuclear@0: 		t0 = t1;
nuclear@0: 	if(t1 < 1e-4)
nuclear@0: 		t1 = t0;
nuclear@0: 
nuclear@0: 	float t = t0 < t1 ? t0 : t1;
nuclear@0: 	if(t < 1e-4)
nuclear@0: 		return false;
nuclear@0: 
nuclear@0: 	// fill the HitPoint structure
nuclear@0: 	pt->obj = this;
nuclear@0: 	pt->dist = t;
nuclear@0: 	pt->pos = ray.origin + ray.dir * t;
nuclear@0: 	pt->normal = (pt->pos - pos) / radius;
nuclear@0: 
nuclear@0: 	pt->pos.transform(xform);
nuclear@0: 	pt->normal.transform(dir_xform);
nuclear@0: 	return true;
nuclear@0: }