MacFluidGrid.h

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#pragma once
#include "common/Export.h"
 
#include "common/Result.h"
#include "graphics/fog/FogDensityField.h"
#include "graphics/fog/FogTypes.h"
#include "graphics/fog/SceneWind.h"
 
#include <cstddef>
#include <cstdint>
#include <vector>
 
#include <glm/vec3.hpp>
 
namespace eve::graphics::fog {
 
class FogInteractor;
 
class EVENGINE_API_WORLD MacFluidGrid {
public:
    static constexpr float kDefaultFixedDt = 1.f / 60.f;
    static constexpr float kMaxAccumulated = 0.25f;
 
    [[nodiscard]] Result<void> configure(const FogDensityField& field, float fixedDt = kDefaultFixedDt);
 
    [[nodiscard]] int width() const noexcept { return width_; }
    [[nodiscard]] int height() const noexcept { return height_; }
    [[nodiscard]] int depth() const noexcept { return depth_; }
    [[nodiscard]] const FogWorldBounds& bounds() const noexcept { return bounds_; }
    [[nodiscard]] glm::vec3 cellSize() const noexcept { return cellSize_; }
    [[nodiscard]] float fixedDt() const noexcept { return fixedDt_; }
    [[nodiscard]] float accumulatedTime() const noexcept { return accumulator_; }
    [[nodiscard]] std::uint64_t stepCount() const noexcept { return stepCount_; }
 
    [[nodiscard]] Result<void> pullDensity(const FogDensityField& field);
    [[nodiscard]] Result<void> pushDensity(FogDensityField& field) const;
 
    [[nodiscard]] float densityAt(int x, int y, int z) const noexcept;
    void setDensity(int x, int y, int z, float density);
 
    [[nodiscard]] float uAt(int i, int y, int z) const noexcept;
    [[nodiscard]] float vAt(int x, int j, int z) const noexcept;
    [[nodiscard]] float wAt(int x, int y, int k) const noexcept;
 
    [[nodiscard]] glm::vec3 velocityAtCell(int x, int y, int z) const noexcept;
 
    [[nodiscard]] Result<FogCflReport> step(float dt, SceneWind& wind, FogInteractor* interactor,
                                           float simTime);
 
    [[nodiscard]] FogCflReport diagnoseCfl() const noexcept;
 
private:
    friend class FogInteractor;
 
    [[nodiscard]] std::size_t cellIndex(int x, int y, int z) const noexcept;
    [[nodiscard]] std::size_t uIndex(int i, int y, int z) const noexcept;
    [[nodiscard]] std::size_t vIndex(int x, int j, int z) const noexcept;
    [[nodiscard]] std::size_t wIndex(int x, int y, int k) const noexcept;
 
    void applyForcesAndWind(const SceneWind& wind, float dt, float simTime);
    void advectVelocity(float dt);
    void projectPressure();
    void advectDensity(float dt, const FogInteractor* interactor);
    [[nodiscard]] glm::vec3 sampleVelocity(const glm::vec3& localCell) const noexcept;
    [[nodiscard]] float sampleDensityLocal(const glm::vec3& localCell) const noexcept;
    [[nodiscard]] glm::vec3 traceBounded(const glm::vec3& start, const glm::vec3& delta,
                                        const FogInteractor* interactor) const noexcept;
 
    int width_ = 0;
    int height_ = 0;
    int depth_ = 0;
    FogWorldBounds bounds_{};
    glm::vec3 cellSize_{1.f};
    float fixedDt_ = kDefaultFixedDt;
    float accumulator_ = 0.f;
    std::uint64_t stepCount_ = 0;
 
    std::vector<float> u_;
    std::vector<float> v_;
    std::vector<float> w_;
    std::vector<float> density_;
    std::vector<float> pressure_;
    std::vector<float> divergence_;
    std::vector<float> tmpDensity_;
    std::vector<float> tmpU_;
    std::vector<float> tmpV_;
    std::vector<float> tmpW_;
    std::vector<std::uint8_t> solid_;
};
 
}  // namespace eve::graphics::fog