world.cpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "game/world.hpp"
#include <engine/color/color.hpp>
#include <engine/config.hpp>
#include <engine/debug/log.hpp>
#include <engine/entity/archetype.hpp>
#include "game/commands/commands.hpp"
#include "game/components/atmosphere-component.hpp"
#include "game/components/blackbody-component.hpp"
#include "game/components/celestial-body-component.hpp"
#include "game/components/observer-component.hpp"
#include "game/components/orbit-component.hpp"
#include "game/components/terrain-component.hpp"
#include "game/components/transform-component.hpp"
#include "game/systems/astronomy-system.hpp"
#include "game/systems/atmosphere-system.hpp"
#include "game/systems/orbit-system.hpp"
#include "game/systems/terrain-system.hpp"
#include <engine/geom/solid-angle.hpp>
#include <engine/gl/vertex-array.hpp>
#include <engine/gl/vertex-buffer.hpp>
#include <engine/i18n/string-table.hpp>
#include <engine/math/hash/hash.hpp>
#include <engine/math/noise/noise.hpp>
#include <engine/math/angles.hpp>
#include <engine/physics/light/photometry.hpp>
#include <engine/physics/light/vmag.hpp>
#include <engine/physics/orbit/ephemeris.hpp>
#include <engine/physics/orbit/orbit.hpp>
#include <engine/physics/time/constants.hpp>
#include <engine/physics/time/gregorian.hpp>
#include <engine/physics/time/utc.hpp>
#include <engine/render/material-flags.hpp>
#include <engine/render/material.hpp>
#include <engine/render/model.hpp>
#include <engine/render/passes/sky-pass.hpp>
#include <engine/render/vertex-attribute-location.hpp>
#include <engine/utility/json.hpp>
#include <engine/resources/resource-manager.hpp>
#include <engine/scene/directional-light.hpp>
#include <engine/scene/text.hpp>
#include <algorithm>
#include <execution>
#include <fstream>
#include <engine/animation/screen-transition.hpp>
#include <engine/animation/ease.hpp>
 
namespace world {
 
static void load_ephemeris(::game& ctx);
 
static void create_stars(::game& ctx);
 
static void create_sun(::game& ctx);
 
static void create_earth_moon_system(::game& ctx);
 
static void create_earth(::game& ctx);
 
static void create_moon(::game& ctx);
 
void cosmogenesis(::game& ctx)
{
    debug::log_trace("Generating cosmos...");
    
    load_ephemeris(ctx);
    create_stars(ctx);
    create_sun(ctx);
    create_earth_moon_system(ctx);
    
    debug::log_trace("Generated cosmos");
}
 
void create_observer(::game& ctx)
{
    debug::log_trace("Creating observer...");
    
    {
        // Create observer entity
        entity::id observer_eid = ctx.entity_registry->create();
        ctx.entities["observer"] = observer_eid;
        
        // Construct observer component
        ::observer_component observer;
        
        // Set observer reference body
        if (auto it = ctx.entities.find("earth"); it != ctx.entities.end())
            observer.reference_body_eid = it->second;
        else
            observer.reference_body_eid = entt::null;
        
        // Set observer location
        observer.elevation = 0.0;
        observer.latitude = 0.0;
        observer.longitude = 0.0;
        
        // Assign observer component to observer entity
        ctx.entity_registry->emplace<::observer_component>(observer_eid, observer);
        
        // Set atmosphere system active atmosphere
        ctx.atmosphere_system->set_active_atmosphere(observer.reference_body_eid);
        
        // Set astronomy system observer
        ctx.astronomy_system->set_observer(observer_eid);
    }
    
    debug::log_trace("Created observer");
}
 
void set_location(::game& ctx, double elevation, double latitude, double longitude)
{
    if (auto it = ctx.entities.find("observer"); it != ctx.entities.end())
    {
        entity::id observer_eid = it->second;
        
        if (ctx.entity_registry->valid(observer_eid) && ctx.entity_registry->all_of<::observer_component>(observer_eid))
        {
            // Update observer location 
            ctx.entity_registry->patch<::observer_component>
            (
                observer_eid,
                [&](auto& component)
                {
                    component.elevation = elevation;
                    component.latitude = latitude;
                    component.longitude = longitude;
                }
            );
        }
    }
}
 
void set_time(::game& ctx, double t)
{
    try
    {
        ctx.astronomy_system->set_time(t);
        ctx.orbit_system->set_time(t);
        
        // debug::log_info("Set time to UT1 {}", t);
    }
    catch (const std::exception& e)
    {
        debug::log_error("Failed to set time to UT1 {}: {}", t, e.what());
    }
}
 
void set_time(::game& ctx, int year, int month, int day, int hour, int minute, double second)
{
    double longitude = 0.0;
    
    // Get longitude of observer
    if (auto it = ctx.entities.find("observer"); it != ctx.entities.end())
    {
        entity::id observer_eid = it->second;
        if (ctx.entity_registry->valid(observer_eid))
        {
            const auto observer = ctx.entity_registry->try_get<::observer_component>(observer_eid);
            if (observer)
                longitude = observer->longitude;
        }
    }
    
    // Calculate UTC offset at longitude
    const double utc_offset = physics::time::utc::offset<double>(longitude);
    
    // Convert time from Gregorian to UT1
    const double t = physics::time::gregorian::to_ut1<double>(year, month, day, hour, minute, second, utc_offset);
    
    set_time(ctx, t);
}
 
void set_time_scale(::game& ctx, double scale)
{
    // Convert time scale from seconds to days
    const double astronomical_scale = scale / physics::time::seconds_per_day<double>;
    
    ctx.orbit_system->set_time_scale(astronomical_scale);
    ctx.astronomy_system->set_time_scale(astronomical_scale);
}
 
void load_ephemeris(::game& ctx)
{
    ctx.orbit_system->set_ephemeris(ctx.resource_manager->load<physics::orbit::ephemeris<double>>("de421.eph"));
}
 
void create_stars(::game& ctx)
{
    debug::log_trace("Generating fixed stars...");
    
    // Load star catalog
    auto star_catalog = ctx.resource_manager->load<i18n::string_table>("hipparcos-7.tsv");
    
    // Allocate star catalog vertex data
    std::size_t star_count = 0;
    if (star_catalog->rows.size() > 0)
        star_count = star_catalog->rows.size() - 1;
    constexpr std::size_t star_vertex_stride = 7 * sizeof(float);
    std::vector<float> star_vertex_data(star_count * star_vertex_stride / sizeof(float));
    float* star_vertex = star_vertex_data.data();
    
    // Init starlight illuminance
    math::dvec3 starlight_illuminance = {0, 0, 0};
    
    // Build star catalog vertex data
    for (std::size_t i = 1; i < star_catalog->rows.size(); ++i)
    {
        const auto& row = star_catalog->rows[i];
        
        // Parse star catalog item
        float ra = 0.0;
        float dec = 0.0;
        float vmag = 0.0;
        float bv = 0.0;
        try
        {
            ra = std::stof(row[1]);
            dec = std::stof(row[2]);
            vmag = std::stof(row[3]);
            bv = std::stof(row[4]);
        }
        catch (const std::exception&)
        {
            debug::log_warning("Invalid star catalog item on row {}", i);
            continue;
        }
        
        // Convert right ascension and declination from degrees to radians
        ra = math::wrap_radians(math::radians(ra));
        dec = math::wrap_radians(math::radians(dec));
        
        // Convert ICRF coordinates from spherical to Cartesian
        math::fvec3 position = physics::orbit::frame::bci::cartesian(math::fvec3{1.0f, dec, ra});
        
        // Convert color index to color temperature
        float cct = color::bv_to_cct(bv);
        
        // Calculate XYZ color from color temperature
        math::fvec3 color_xyz = color::cct_to_xyz(cct);
        
        // Transform XYZ color to RGB
        math::fvec3 color_rgb = config::scene_linear_color_space<float>.from_xyz * color_xyz;
        
        // Convert apparent magnitude to brightness factor relative to a 0th magnitude star
        float brightness = physics::light::vmag::to_brightness(vmag);
        
        // Build vertex
        *(star_vertex++) = position.x();
        *(star_vertex++) = position.y();
        *(star_vertex++) = position.z();
        *(star_vertex++) = color_rgb.x();
        *(star_vertex++) = color_rgb.y();
        *(star_vertex++) = color_rgb.z();
        *(star_vertex++) = brightness;
        
        // Calculate spectral illuminance
        math::dvec3 illuminance = math::dvec3(color_rgb * physics::light::vmag::to_illuminance(vmag));
        
        // Add spectral illuminance to total starlight illuminance
        starlight_illuminance += illuminance;
    }
    
    // Allocate stars model
    std::shared_ptr<render::model> stars_model = std::make_shared<render::model>();
    
    // Construct stars VAO
    constexpr gl::vertex_input_attribute star_vertex_attributes[] =
    {
        {
            render::vertex_attribute_location::position,
            0,
            gl::format::r32g32b32_sfloat,
            0
        },
        {
            render::vertex_attribute_location::color,
            0,
            gl::format::r32g32b32a32_sfloat,
            3 * sizeof(float)
        }
    };
    auto& vao = stars_model->get_vertex_array();
    vao = std::make_unique<gl::vertex_array>(star_vertex_attributes);
    
    // Construct stars VBO
    auto& vbo = stars_model->get_vertex_buffer();
    vbo = std::make_unique<gl::vertex_buffer>(gl::buffer_usage::static_draw, std::as_bytes(std::span{star_vertex_data}));
    stars_model->set_vertex_offset(0);
    stars_model->set_vertex_stride(star_vertex_stride);
    
    // Construct star model group
    stars_model->get_groups().resize(1);
    render::model_group& stars_model_group = stars_model->get_groups().front();
    stars_model_group.id = "stars";
    stars_model_group.material = ctx.resource_manager->load<render::material>("fixed-star.mtl");
    stars_model_group.primitive_topology = gl::primitive_topology::point_list;
    stars_model_group.first_vertex = 0;
    stars_model_group.vertex_count = static_cast<std::uint32_t>(star_count);
    
    // Pass stars model to sky pass
    ctx.sky_pass->set_stars_model(stars_model);
    
    // Pass starlight illuminance to astronomy system
    ctx.astronomy_system->set_starlight_illuminance(starlight_illuminance);
    
    debug::log_trace("Generated fixed stars");
}
 
void create_sun(::game& ctx)
{
    debug::log_trace("Generating Sun...");
    
    {
        // Create sun entity
        auto sun_archetype = ctx.resource_manager->load<entity::archetype>("sun.ent");
        entity::id sun_eid = sun_archetype->create(*ctx.entity_registry);
        ctx.entities["sun"] = sun_eid;
        
        // Create sun directional light scene object
        ctx.sun_light = std::make_unique<scene::directional_light>();
        ctx.sun_light->set_shadow_caster(true);
        ctx.sun_light->set_shadow_framebuffer(ctx.shadow_map_framebuffer);
        ctx.sun_light->set_shadow_bias(0.005f);
        ctx.sun_light->set_shadow_max_distance(20.0f);
        ctx.sun_light->set_shadow_fade_range(5.0f);
        ctx.sun_light->set_shadow_cascade_count(4);
        ctx.sun_light->set_shadow_cascade_distribution(0.8f);
        
        // Add sun light scene objects to surface scene
        ctx.surface_scene->add_object(*ctx.sun_light);
        
        // Pass direct sun light scene object to shadow map pass and astronomy system
        ctx.astronomy_system->set_sun_light(ctx.sun_light.get());
    }
    
    debug::log_trace("Generated Sun");
}
 
void create_earth_moon_system(::game& ctx)
{
    debug::log_trace("Generating Earth-Moon system...");
    
    {
        // Create Earth-Moon barycenter entity
        auto em_bary_archetype = ctx.resource_manager->load<entity::archetype>("em-bary.ent");
        entity::id em_bary_eid = em_bary_archetype->create(*ctx.entity_registry);
        ctx.entities["em_bary"] = em_bary_eid;
        
        // Create Earth
        create_earth(ctx);
        
        // Create Moon
        create_moon(ctx);
    }
    
    debug::log_trace("Generated Earth-Moon system");
}
 
void create_earth(::game& ctx)
{
    debug::log_trace("Generating Earth...");
    
    {
        // Create earth entity
        auto earth_archetype = ctx.resource_manager->load<entity::archetype>("earth.ent");
        entity::id earth_eid = earth_archetype->create(*ctx.entity_registry);
        ctx.entities["earth"] = earth_eid;
        
        // Assign orbital parent
        ctx.entity_registry->get<::orbit_component>(earth_eid).parent = ctx.entities["em_bary"];
    }
    
    debug::log_trace("Generated Earth");
}
 
void create_moon(::game& ctx)
{
    debug::log_trace("Generating Moon...");
    
    {
        // Create lunar entity
        auto moon_archetype = ctx.resource_manager->load<entity::archetype>("moon.ent");
        entity::id moon_eid = moon_archetype->create(*ctx.entity_registry);
        ctx.entities["moon"] = moon_eid;
        
        // Assign orbital parent
        ctx.entity_registry->get<::orbit_component>(moon_eid).parent = ctx.entities["em_bary"];
        
        // Pass moon model to sky pass
        ctx.sky_pass->set_moon_model(ctx.resource_manager->load<render::model>("moon.mdl"));
        
        // Create moon directional light scene object
        ctx.moon_light = std::make_unique<scene::directional_light>();
        
        // Add moon light scene objects to surface scene
        ctx.surface_scene->add_object(*ctx.moon_light);
        
        // Pass moon light scene object to astronomy system
        ctx.astronomy_system->set_moon_light(ctx.moon_light.get());
    }
    
    debug::log_trace("Generated Moon");
}
 
void enter_ecoregion(::game& ctx, const ecoregion& ecoregion)
{   
    debug::log_trace("Entering ecoregion {}...", ecoregion.name);
    {
        // Set active ecoregion
        //ctx.active_ecoregion = &ecoregion;
        
        // Set location
        ::world::set_location(ctx, ecoregion.elevation, ecoregion.latitude, ecoregion.longitude);
        
        // Setup sky
        ctx.sky_pass->set_sky_model(ctx.resource_manager->load<render::model>("celestial-hemisphere.mdl"));
        ctx.sky_pass->set_ground_albedo(ecoregion.terrain_albedo);
        
        // Setup terrain
        // ctx.terrain_system->set_patch_material(ecoregion.terrain_material);
        // ctx.terrain_system->set_elevation_function
        // (
            // [](float x, float z) -> float
            // {
                // const math::fvec2 position = math::fvec2{x, z};
 
                // const std::size_t octaves = 3;
                // const float lacunarity = 1.5f;
                // const float gain = 0.5f;
                
                // const float fbm = math::noise::fbm
                // (
                    // position * 0.005f,
                    // octaves,
                    // lacunarity,
                    // gain
                // );
                
                // float y = fbm * 4.0f;
                
                // return y;
            // }
        // );
    }
    
    debug::log_trace("Entered ecoregion {}", ecoregion.name);
}
 
void switch_scene(::game& ctx)
{
    ctx.fade_transition_color->set({0, 0, 0});
    ctx.fade_transition->transition(1.0f, false, ease<float>::out_cubic, false, [](){});
}
 
} // namespace world