libcruft-util/geom/aabb.hpp

/*
 * 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 2015-2017 Danny Robson <danny@nerdcruft.net>
 */


#ifndef CRUFT_UTIL_GEOM_AABB_HPP
#define CRUFT_UTIL_GEOM_AABB_HPP

#include "../debug.hpp"
#include "../extent.hpp"
#include "../point.hpp"

#include <cstdint>

namespace util::geom {
    ///////////////////////////////////////////////////////////////////////////
    /// represents an axis-aligned bounding-box through two opposing corners.
    ///
    /// `lo' must be less-than-or-equal to `hi'. equality is allowed so that
    /// we can represent zero sized bounding-boxes.
    template <size_t S, typename T>
    struct aabb {
        aabb () = default;
        aabb (point<S,T> _lo, point<S,T> _hi):
            lo (_lo),
            hi (_hi)
        {
            CHECK (all (lo <= hi));
        }


        ///////////////////////////////////////////////////////////////////////
        extent<S,T>
        magnitude (void) const
        {
            return (hi - lo).template as<util::extent> ();
        }


        //---------------------------------------------------------------------
        T
        diameter (void) const
        {
            return magnitude ().diameter ();
        }


        //---------------------------------------------------------------------
        /// tests whether a point lies within the region, inclusive of borders
        constexpr bool
        inclusive (point<S,T> p) const noexcept
        { return all (lo <= p && hi >= p); }


        //---------------------------------------------------------------------
        point<S,T>
        closest (point<S,T> query) const
        {
            return clamp (query, lo, hi);
        }


        //---------------------------------------------------------------------
        void cover (point<S,T> p)
        {
            lo = min (p, lo);
            hi = max (p, hi);
        }


        //---------------------------------------------------------------------
        aabb<S,T> operator+ (vector<S,T> v) const
        {
            return { lo + v, hi + v };
        }


        aabb<S,T> operator- (vector<S,T> v) const
        {
            return { lo - v, hi - v };
        }


        /// returns an aabb that covers the supplied point in addition to the
        /// current aabb area.
        auto operator| [[nodiscard]] (point<S,T> p) const noexcept
        {
            return aabb (
                util::min (lo, p),
                util::max (hi, p)
            );
        }


        auto& operator|= (point<S,T> p) noexcept
        {
            return *this = *this | p;
        }

        aabb operator| [[nodiscard]] (aabb<S,T> rhs) const noexcept
        {
            return {
                min (lo, rhs.lo),
                max (hi, rhs.hi)
            };
        }

        std::array<util::point<S,T>,util::pow(2,S)>
        vertices (void) const noexcept;


        ::util::point<S,T> lo;
        ::util::point<S,T> hi;
    };


    ///////////////////////////////////////////////////////////////////////////
    template <std::size_t S, typename T>
    constexpr bool
    operator== (const aabb<S,T> &a, const aabb<S,T> &b) noexcept
    {
        return a.lo == b.lo && a.hi == b.hi;
    }


    ///////////////////////////////////////////////////////////////////////////
    typedef aabb<2,float> aabb2f;
    typedef aabb<2,unsigned> aabb2u;
    typedef aabb<2,int> aabb2i;

    typedef aabb<3,float> aabb3f;
    typedef aabb<3,unsigned> aabb3u;
    typedef aabb<3,int> aabb3i;
}


///////////////////////////////////////////////////////////////////////////////
#include "./sample.hpp"

#include <random>

namespace util::geom {
    template <size_t S, typename T, typename G>
    struct sampler<S,T,aabb,G> {
        static point<S,T>
        fn (aabb<S,T> b, G &g)
        {
            std::uniform_real_distribution<T> d;

            point<S,T> p;
            std::generate (p.begin (), p.end (), [&] (void) { return d (g); });

            return p * (b.hi - b.lo) + b.lo.template as<util::vector> ();
        }
    };
}

#endif