libcruft-util/geom/ellipse.hpp

/*
 * 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 *
 * Copyright 2015 Danny Robson <danny@nerdcruft.net>
 */

#ifndef __UTIL_GEOM_ELLIPSE_HPP
#define __UTIL_GEOM_ELLIPSE_HPP

#include <cstdlib>

#include "fwd.hpp"

#include "../point.hpp"
#include "../vector.hpp"

namespace util::geom {
    ///////////////////////////////////////////////////////////////////////////
    template <size_t S, typename ValueT>
    struct ellipse {
        // the centre point of the ellipsoid
        util::point<S,ValueT> origin;

        // the distance from the centre along each axis to the shape's edge
        util::vector<S,ValueT> radius;

        // the orientation of up for the shape
        util::vector<S,ValueT> up;
    };


    /// returns the distance along a ray to the surface of an ellipse.
    ///
    /// returns infinity if there is no intersection
    template <size_t DimensionV, typename ValueT>
    ValueT
    distance (
        ray<DimensionV,ValueT>,
        ellipse<DimensionV,ValueT>
    );

    using ellipse3f = ellipse<3,float>;
}


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

#include <cmath>
#include <random>

namespace util::geom {
    template <typename T, template <size_t,typename> class K, typename G>
    struct sampler<2,T,K,G>
    {
        static util::point<2,T> fn (K<2,T> k, G &g)
        {
            std::uniform_real_distribution<T> dist;

            float phi = dist (g) * 2 * pi<T>;
            float rho = std::sqrt (dist (g));

            return util::point<2,T> {
                std::cos (phi),
                std::sin (phi)
            } * rho * k.radius + k.origin.template as<util::vector> ();
        }
    };
}

#endif