TrailEffect.h

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#pragma once
#include "common/Export.h"
 
 
#include <glm/vec2.hpp>
#include <glm/vec3.hpp>
 
#include <cstddef>
#include <cstdint>
#include <deque>
#include <vector>
 
namespace eve::stylize {
 
struct TrailSettings {
    std::size_t maxSamples = 48;
    float lifetime = 0.28f;
    float minSampleDistance = 0.015f;
    float teleportDistance = 2.f;
};
 
enum class TrailAppendResult { Added, StartedSegment, SkippedTooClose };
 
struct TrailSample {
    glm::vec3 root{0.f};
    glm::vec3 tip{0.f};
    float age = 0.f;
    std::uint32_t segment = 0;
};
 
struct TrailVertex {
    glm::vec3 position{0.f};
    glm::vec2 uv{0.f};
    float alpha = 0.f;
};
 
struct TrailMeshSnapshot {
    std::vector<TrailVertex> vertices;
    std::vector<std::uint32_t> indices;
};
 
class EVENGINE_API_WORLD TrailEmitter {
public:
    explicit TrailEmitter(TrailSettings settings = {});
    TrailEmitter(const TrailEmitter&) = delete;
    TrailEmitter& operator=(const TrailEmitter&) = delete;
 
    void setSettings(TrailSettings settings);
    [[nodiscard]] TrailSettings settings() const noexcept { return settings_; }
    void update(float dtSeconds);
    [[nodiscard]] TrailAppendResult append(glm::vec3 root, glm::vec3 tip);
    void breakTrail() noexcept;
    void clear() noexcept;
    [[nodiscard]] std::size_t sampleCount() const noexcept { return samples_.size(); }
    [[nodiscard]] TrailMeshSnapshot buildMesh() const;
 
private:
    static void validateSettings(const TrailSettings& settings);
 
    TrailSettings settings_;
    std::deque<TrailSample> samples_;
    std::uint32_t segment_ = 0;
    bool forceBreak_ = true;
};
 
}  // namespace eve::stylize