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<?php
/**
* Copyright 2011, Alok Menghrajani. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are
* permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of
* conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list
* of conditions and the following disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation are those of the
* authors and should not be interpreted as representing official policies, either expressed
* or implied, of the author.
*/
class Sphere extends Object {
protected $radius = 1;
public function intersect(Ray $ray, $compute_point, $compute_normal) {
// A sphere-ray intersection can happen in 0, 1 or 2 points
$dst = clone $ray->getOrigin();
$dst->V_sub($this->position);
$b = Vector::dot($dst, $ray->getDirection());
$c = Vector::dot($dst, $dst) - $this->radius * $this->radius;
$d = $b * $b - $c;
if ($d < 0) {
return null;
}
$t = -$b - sqrt($d);
if ($t < 0) {
return null;
}
$r = array('d' => $t);
if ($compute_point || $compute_normal) {
$t2 = clone $ray->getDirection();
$t2->K_mul($t);
$t2->V_add($ray->getOrigin());
$r['p'] = $t2;
}
if ($compute_normal) {
$n = clone $this->position;
$n->neg();
$n->V_add($t2);
$n->normalize();
$r['n'] = $n;
}
return $r;
}
public function setRadius($r) {
$this->radius = (float)$r;
return $this;
}
}
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