struct IWeaponFiringLocator {
};

IWeapon.h

virtual ~IWeaponFiringLocator();

virtual bool GetActualWeaponDir(EntityId weaponId, const IFireMode* pFireMode, Vec3& dir, const Vec3& probableHit, const Vec3& firingPos) = 0;

this is acutal weapon direction

virtual bool GetFiringDir(EntityId weaponId, const IFireMode* pFireMode, Vec3& dir, const Vec3& probableHit, const Vec3& firingPos) = 0;

this is target pos - firing pos

virtual bool GetFiringPos(EntityId weaponId, const IFireMode* pFireMode, Vec3& pos) = 0;

position of the projectile

virtual bool GetFiringVelocity(EntityId weaponId, const IFireMode* pFireMode, Vec3& vel, const Vec3& firingDir) = 0;

velocity to add up to the projectile (usually host velocity)

virtual bool GetProbableHit(EntityId weaponId, const IFireMode* pFireMode, Vec3& hit) = 0;

probable hit position

virtual void WeaponReleased() = 0;

called when weapon is deleted