SkyAtmospherePass.h

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#pragma once
#include <array>
#include <glm/mat4x4.hpp>
#include <glm/vec3.hpp>
#include <memory>
#include "common/Export.h"
#include "common/Result.h"
 
namespace eve::graphics {
class Graphics;
struct SkyWispsLayer;
 
struct SkyHeightFogParameters {
    std::array<float, 2> directionalElevationRange{0, 0};
    float                densityPerMetre       = 0;
    float                heightFalloffPerMetre = .006f;
    float                baseHeightMetres      = -1.5f;
    float                startDistanceMetres   = 73.4803369f;
    std::array<float, 3> inscattering{0, 0, 0};
    float                maximumOpacity = 1;
    std::array<float, 3> directionalInscattering{.78809762f, .64244735f, .55544519f};
    float                directionalExponent            = 5;
    float                directionalStartDistanceMetres = 100;
    float                atmosphereContribution         = 2.3f;
    float                skyDistanceMetres              = 100000;
    [[nodiscard]] EVENGINE_API_BACKENDS Result<void> validate() const;
};
 
struct SkyAtmosphereParameters {
    std::array<float, 3>   rayleigh{.0067450796f, .0163137194f, .04f};
    float                  rayleighHeightKm = 8;
    std::array<float, 3>   mieScattering{.0112259542f, .0123162284f, .013996f};
    float                  mieHeightKm = 1.2f;
    std::array<float, 3>   mieAbsorption{.000444f, .000444f, .000444f};
    float                  mieAnisotropy = .75f;
    std::array<float, 3>   ozoneAbsorption{.001794476f, .002f, .000190614f};
    float                  ozoneCenterKm      = 25;
    float                  ozoneHalfWidthKm   = 15;
    float                  groundRadiusKm     = 6360;
    float                  atmosphereHeightKm = 60;
    std::array<float, 3>   groundAlbedo{.40197778f, .40197778f, .40197778f};
    float                  multiScatteringFactor = 1;
    SkyHeightFogParameters heightFog;
    [[nodiscard]] EVENGINE_API_BACKENDS Result<void> validate() const;
};
 
struct SkyCelestialLight {
    glm::vec3 direction{-.5f, .8660254f, 0};
    glm::vec3 irradiance{5.f};
};
 
struct SkyAtmosphereFrame {
    SkyCelestialLight sun;
    float             wispsMorphPhase = 0;  // Normalized periodic phase in [0,1).
    float dayPhase = 0;
};
 
class EVENGINE_API_BACKENDS SkyAtmospherePass {
public:
    [[nodiscard]] static Result<std::unique_ptr<SkyAtmospherePass>> prepare(Graphics&                      graphics,
                                                                            const SkyAtmosphereParameters& parameters,
                                                                            const SkyWispsLayer* wisps = nullptr);
    ~SkyAtmospherePass();
    SkyAtmospherePass(const SkyAtmospherePass&)            = delete;
    SkyAtmospherePass& operator=(const SkyAtmospherePass&) = delete;
    [[nodiscard]] Result<void> setLight(const SkyCelestialLight& light);
    [[nodiscard]] Result<void> setFrame(const SkyAtmosphereFrame& frame);
    [[nodiscard]] Result<void> attach();
    void detach() noexcept;
    [[nodiscard]] Result<void> prepareView(const glm::mat4& viewProjection, const glm::vec3& eyeMetres);
    [[nodiscard]] Result<void> draw(const glm::mat4& viewProjection, const glm::vec3& eyeMetres);
 
private:
    [[nodiscard]] Result<void> drawView(const glm::mat4&, const glm::vec3&, bool reflection);
    SkyAtmospherePass();
    struct Impl;
    std::unique_ptr<Impl> impl_;
};
}  // namespace eve::graphics