libcruft-util/geom/segment.hpp

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/*
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
*/
#pragma once
#include "../point.hpp"
namespace cruft::geom {
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/// Represents a line that has a start and an end.
///
/// It is not valid to create an unbounded segment by fixing one of the
/// points at infinity.
template <size_t S, typename T>
struct segment {
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cruft::point<S,T> a; /// The start of the segment.
cruft::point<S,T> b; /// The end of the segment.
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/// Return a copy of this object with the underlying type casted to
/// the specified type.
template <typename CastT>
segment<S,CastT>
cast (void) const {
return {
.a = a.template cast<CastT> (),
.b = b.template cast<CastT> ()
};
}
};
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/// Return the squared distance from the closest point of the segment `s`
/// to the point `p`.
template <size_t S, typename T>
T
distance2 (segment<S,T> s, point<S,T> p)
{
const auto dir = s.b - s.a;
const auto t1 = dot (p - s.a, dir);
if (t1 < 0)
return distance2 (p, s.a);
const auto t2 = dot (dir, dir);
if (t2 < t1)
return distance2 (p, s.b);
auto t = t1 / t2;
return distance2 (p, s.a + t * dir);
}
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/// Return the distance from a the closest point of the segment `s` to
/// the point `p`.
template <size_t S, typename T>
T
distance (segment<S,T> s, point<S,T> p)
{
return std::sqrt (distance2 (s, p));
}
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/// Returns the un-normalised direction of the segment from its start to
/// end components. ie, `a' to `b'.
template <size_t S, typename T>
cruft::vector<S,T>
udirection (segment<S,T> const &val)
{
return val.b - val.a;
}
/// Returns the normalised direction of the segment.
template <size_t S, typename T>
cruft::vector<S,T>
ndirection (segment<S,T> const &val)
{
return normalised (udirection (val));
}
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using segment2i = segment<2,int>;
using segment3i = segment<3,int>;
using segment2f = segment<2,float>;
using segment3f = segment<3,float>;
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template <size_t S, typename T>
segment (point<S,T>, point<S,T>) -> segment<S,T>;
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}