init

engine/include/hd2d/Particles.h

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+#pragma once
+#include "hd2d/GL.h"
+
+#include <glm/glm.hpp>
+#include <random>
+#include <vector>
+
+namespace hd2d {
+
+struct PointLight;
+
+// High-resolution (non pixel-art) particles: ambient fields (fireflies, dust),
+// fire emitters (flames, embers, smoke, glow + flickering light) and bursts.
+class ParticleSystem {
+public:
+    // Must match the kind ids in particles.vert / particles.frag.
+    enum class Kind : int {
+        Firefly = 0,  // blinking emissive glow, wanders near the ground
+        Mote = 1,     // dust speck only visible where sunlight hits it (god rays)
+        Spark = 2,    // ballistic burst particle (footstep dust, rain splashes, ...)
+        Flame = 3,    // additive tongue of fire, eroded by noise as it ages
+        Ember = 4,    // tiny hot spark drifting up on turbulent air
+        Smoke = 5,    // alpha-blended puff rising above a fire
+        Glow = 6,     // large soft halo around a fire (one per emitter per frame)
+    };
+
+    struct Field {  // region that keeps a constant population of ambient particles
+        Kind kind;
+        glm::vec3 min, max;
+        int count;
+    };
+
+    struct Fire {
+        glm::vec3 pos;      // base of the flames
+        float scale = 1.0f; // overall size / intensity
+        float flameAccum = 0.0f, emberAccum = 0.0f, smokeAccum = 0.0f;
+        float flicker = 1.0f;  // current light flicker multiplier
+        float phase = 0.0f;
+    };
+
+    ~ParticleSystem();
+    void addField(Kind kind, glm::vec3 min, glm::vec3 max, int count);
+    int addFire(glm::vec3 pos, float scale = 1.0f);
+    void burst(glm::vec3 pos, int count, glm::vec3 color, float speed, float size, float life);
+    void update(float dt, float time);
+    void draw() const;
+    // Appends fire lights first, then up to `maxFireflies` firefly lights.
+    void collectLights(std::vector<PointLight>& out, int maxFireflies) const;
+    const std::vector<Fire>& fires() const { return fires_; }
+
+    glm::vec3 fireflyColor{2.6f, 3.2f, 0.9f};
+    glm::vec3 moteColor{1.0f, 0.95f, 0.8f};
+    float fireflyLightRadius = 2.2f;
+    glm::vec3 fireLightColor{4.0f, 1.75f, 0.55f};
+    float fireLightRadius = 7.0f;
+    glm::vec3 wind{0.0f};       // world-space drift applied to smoke and embers
+    float ambientFade = 1.0f;   // scales fireflies + motes (Weather lowers it in rain)
+
+private:
+    struct Particle {
+        glm::vec3 pos, vel;
+        glm::vec3 color;
+        float size, age, life, phase;
+        Kind kind;
+        int field;  // ambient field index, or -1
+        int fire;   // owning fire, or -1
+    };
+    struct GpuParticle {
+        glm::vec4 posSize;
+        glm::vec4 color;   // rgb, a = alpha
+        glm::vec4 params;  // x = kind, y = age / life, z = random seed
+    };
+    void spawnInField(Particle& p, int fieldIndex, bool randomAge);
+    void spawnFire(const Fire& f, int fireIndex, Kind kind);
+
+    std::vector<Field> fields_;
+    std::vector<Fire> fires_;
+    std::vector<Particle> particles_;
+    std::vector<GpuParticle> gpu_;
+    std::mt19937 rng_{1337};
+    GLuint vao_ = 0, vbo_ = 0;
+    size_t capacity_ = 0;
+};
+
+}  // namespace hd2d