TeslaBeamEffect.hpp

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#pragma once
 
#include "particles/ParticleTypes.hpp"
 
#include <cstdint>
#include <glm/glm.hpp>
#include <vector>

class TeslaBeamEffect
{
public:
    void drive(uint32_t key, glm::vec3 origin, glm::vec3 target);

    void update(float dt, glm::vec3 camForward);

    [[nodiscard]] const ArcVertex* arcData() const { return arcVerts_.data(); }

    [[nodiscard]] uint32_t arcCount() const { return static_cast<uint32_t>(arcVerts_.size()); }

    [[nodiscard]] uint32_t activeBeamCount() const;
 
private:
    static constexpr int k_maxBeams = 4;
    static constexpr int k_bezierSegs = 28;        
    static constexpr int k_branchSegs = 6;         
    static constexpr int k_maxBranches = 3;
    static constexpr float k_fadeTime = 0.08f;     
    static constexpr float k_keepAlive = 0.06f;    
    static constexpr float k_bowFrac = 0.16f;      
    static constexpr float k_branchRetime = 0.05f; 

    struct Branch
    {
        float tStart; 
        float length; 
        float angle;  
        float seed;   
    };

    struct Beam
    {
        uint32_t key = 0;
        bool active = false;
        glm::vec3 origin{0.0f};
        glm::vec3 target{0.0f};
 
        float age = 0.f;       
        float keepAlive = 0.f; 
        float time = 0.f;      
        float seed = 0.f;
        float warpSeed = 0.f;
 
        Branch branches[k_maxBranches]{};
        int branchCount = 0;
        float branchTimer = 0.f;
    };
 
    Beam beams_[k_maxBeams]{};
    std::vector<ArcVertex> arcVerts_;
 
    static glm::vec3 evalBezier(glm::vec3 p0, glm::vec3 p1, glm::vec3 p2, glm::vec3 p3, float t);
    static glm::vec3 evalBezierTangent(glm::vec3 p0, glm::vec3 p1, glm::vec3 p2, glm::vec3 p3, float t);
    static void rerandomizeBranches(Beam& beam);

    void appendArcStrip(const std::vector<glm::vec3>& pts, float radius, glm::vec4 color, glm::vec3 camForward);
 
    Beam* findOrAllocBeam(uint32_t key);
};