3D particle system structs (full source: https://github.com/thi-ng/ws-ldn-8/blob/master/day3/ex07/particles.c)

particles.c

// particle system structs

typedef struct {
  float x,y,z;
} Vec3;

typedef struct {
  Vec3 pos; // 12 bytes
  Vec3 vel; // 12 bytes
  Vec3 col; // 12 bytes
} Particle;

typedef struct {
  Particle *particles;
  uint32_t numParticles;
  uint32_t maxParticles;
  Vec3 emitPos;
  Vec3 emitDir;
  Vec3 gravity;
  float speed;
  uint32_t age;
  uint32_t maxAge;
} ParticleSystem;