random_geom.h

 
#pragma once
 
#include "random.h"
#include "rec2.h"
#include "geometry/ellipse.h"
#include "geometry/polygon.h"
#include "geometry/shape_concepts.h"
#define GLM_ENABLE_EXPERIMENTAL 1
#include <glm/ext/scalar_constants.hpp>
#include <glm/gtx/rotate_vector.hpp>
 
namespace ghassanpl::random
{
    
    template <std::floating_point T = float, typename RANDOM = std::default_random_engine>
    [[nodiscard]] T radians(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        static std::uniform_real_distribution<T> dist{ T{}, glm::pi<T>() * 2 };
        return dist(rng);
    }
 
    template <std::floating_point T = float, typename RANDOM = std::default_random_engine>
    [[nodiscard]] T degrees(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        static std::uniform_real_distribution<T> dist{ T{}, T{360} };
        return dist(rng);
    }
 
    template <std::floating_point T = float, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> unit_vector(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        return glm::rotate(glm::tvec2<T>{ T{ 1 }, T{ 0 } }, radians<T>(rng));
    }
 
    template <typename T, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_in(trec2<T> const& rect, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        return { in_range(rect.p1.x, rect.p2.x, rng), in_range(rect.p1.y, rect.p2.y, rng) };
    }
 
    template <typename T, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_in(glm::tvec2<T> const& max, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        return { in_range(T{}, max.x, rng), in_range(T{}, max.y, rng) };
    }

    template <typename T, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_in(geometry::tellipse<T> const& el, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        const auto phi = between(T{}, glm::two_pi<T>(), rng);
        const auto p = glm::tvec2<T>{ cos(phi), sin(phi) } * glm::sqrt(percentage<T>(rng)) * el.radii * T(0.5);
        return p + el.center;
    }
 
    template <typename T, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_in(geometry::ttriangle<T> const& tr, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        const auto r1 = glm::sqrt(percentage<T>(rng));
        const auto r2 = percentage<T>(rng);
 
        return (tr.a * (T(1) - r1) + tr.b * (r1 * (T(1) - r2)) + tr.c * (r2 * r1));
    }
 
    template <typename T, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_in(geometry::immutable::tpolygon<T> const& poly, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        if (poly.triangles().empty()) return {};
 
        auto r = between(T{}, poly.calculate_area());
        size_t i = 0;
        while (r > 0.0)
        {
            if (!poly.has_triangle(i))
                return {};
 
            r -= poly.triangle_area(i);
            if (r <= 0.0)
                break;
            i++;
        }
 
        return point_in(poly.triangle(i), rng);
    }

    template <typename T, geometry::shape<T> S, typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::tvec2<T> point_on(S const& shape, RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        return shape.edge_point_alpha(percentage(rng));
    }
 
    // TODO: in(circle), in(poly)?, on(rect), on(circle), on(arc)
    /*
    template <typename T>
    auto RandomNotIn(ghassanpl::trec2<T> const& verboten, ghassanpl::trec2<T> const& bounds)
    {
        const std::array<ghassanpl::trec2<T>, 4> surrounding = {
            ghassanpl::trec2<T>{ bounds.p1.x, bounds.p1.y, bounds.p2.x, verboten.p1.y },
            ghassanpl::trec2<T>{ bounds.p1.x, verboten.p2.y, bounds.p2.x, bounds.p2.y },
            ghassanpl::trec2<T>{ bounds.p1.x, bounds.p1.y, verboten.p1.x, bounds.p2.y },
            ghassanpl::trec2<T>{ verboten.p2.x, bounds.p1.y, bounds.p2.x, bounds.p2.y },
        };
        const std::array<T, 4> areas = {
            surrounding[0].calculate_area(),
            surrounding[1].calculate_area(),
            surrounding[2].calculate_area(),
            surrounding[3].calculate_area()
        };
        const int total_area = areas[0] + areas[1] + areas[2] + areas[3];
        const int rand_pos = RandomIn(total_area);
        if (rand_pos < areas[0]) return Random(surrounding[0]);
        if (rand_pos < areas[0] + areas[1]) return Random(surrounding[1]);
        if (rand_pos < areas[0] + areas[1] + areas[2]) return Random(surrounding[2]);
        return Random(surrounding[3]);
    }
    */
 
    template <typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::ivec2 neighbor(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        static std::uniform_int_distribution<typename RANDOM::result_type> dist{ 0, 3 };
        switch (dist(rng))
        {
        case 0: return { 1.0f, 0.0f };
        case 1: return { 0.0f, 1.0f };
        case 2: return { -1.0f, 0.0f };
        case 3: return { 0.0f, -1.0f };
        }
        return {};
    }
 
    template <typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::ivec2 diagonal_neighbor(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        static std::uniform_int_distribution<typename RANDOM::result_type> dist{ 0, 3 };
        switch (dist(rng))
        {
        case 0: return { 1.0f, 1.0f };
        case 1: return { -1.0f, 1.0f };
        case 2: return { -1.0f, -1.0f };
        case 3: return { 1.0f, -1.0f };
        }
        return {};
    }
 
    template <typename RANDOM = std::default_random_engine>
    [[nodiscard]] glm::ivec2 surrounding(RANDOM& rng = ::ghassanpl::random::default_random_engine)
    {
        static std::uniform_int_distribution<typename RANDOM::result_type> dist{ 0, 7 };
        switch (dist(rng))
        {
        case 0: return { 1.0f, 0.0f };
        case 1: return { 0.0f, 1.0f };
        case 2: return { -1.0f, 0.0f };
        case 3: return { 0.0f, -1.0f };
        case 4: return { 1.0f, 1.0f };
        case 5: return { -1.0f, 1.0f };
        case 6: return { -1.0f, -1.0f };
        case 7: return { 1.0f, -1.0f };
        }
        return {};
    }
 
    // TODO: Should we move the below to random_seq?
    
    template <std::floating_point T = float>
    [[nodiscard]] constexpr glm::tvec2<T> halton_sequence_2d(size_t index, size_t base_x = 2, size_t base_y = 3)
    {
        return { halton_sequence<T>(index, base_x), halton_sequence<T>(index, base_y) };
    }

 
}