libcruft-util/ray.cpp

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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
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*
* Copyright 2015 Danny Robson <danny@nerdcruft.net>
*/
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#include "ray.hpp"
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#include "debug.hpp"
//-----------------------------------------------------------------------------
template <size_t S, typename T>
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util::ray<S,T>::ray (util::point<S,T> _p,
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util::vector<S,T> _d):
p (_p),
d (_d)
{
CHECK_EQ (d.magnitude2 (), 1);
}
///----------------------------------------------------------------------------
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/// returns the distance along the ray in a ray-plane intersection
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///
/// returns inf if parallel
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/// returns 0 if corayar
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template <size_t S, typename T>
T
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util::ray<S,T>::intersect (plane<S,T> q) const
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{
return dot (q.p - p, q.n) / dot (d, q.n);
}
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///----------------------------------------------------------------------------
/// returns the distance from origin to AABB intersection
///
/// returns NaN on miss
/// returns -ve if behind
template <size_t S, typename T>
T
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util::ray<S,T>::intersect (AABB<S,T> r) const
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{
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auto t1 = (r.p0 - p) / d;
auto t2 = (r.p1 - p) / d;
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auto vmin = min (t1, t2);
auto vmax = max (t1, t2);
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auto tmin = max (vmin);
auto tmax = min (vmax);
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if (tmax < 0)
return tmax;
if (tmin > tmax)
return std::numeric_limits<T>::quiet_NaN ();
return tmin;
}
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///----------------------------------------------------------------------------
/// returns the smallest distance from ray origin to a sphere intersection
///
/// returns NaN on miss
template <size_t S, typename T>
T
util::ray<S,T>::intersect (sphere<S,T> s) const
{
T b = dot (d, p - s.c);
T c = dot (p - s.c, p - s.c) - s.r * s.r;
T D = b * b - c;
if (D < 0)
return std::numeric_limits<T>::quiet_NaN ();
auto t_ = std::sqrt (D);
auto t0 = -b + t_;
auto t1 = -b - t_;
return t1 >= 0 ? t1 :
t0 >= 0 ? t0 :
std::numeric_limits<T>::quiet_NaN ();
}
///----------------------------------------------------------------------------
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/// returns the closest parameter along the ray to a given point
template <size_t S, typename T>
T
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util::ray<S,T>::closest (point<S,T> q) const
{
// project the origin-point difference onto the direction
return dot (p - q, d);
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}
//-----------------------------------------------------------------------------
template <size_t S, typename T>
util::point<S,T>
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util::ray<S,T>::at (T t) const
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{
return p + d * t;
}
//-----------------------------------------------------------------------------
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template struct util::ray<2,float>;
template struct util::ray<3,float>;