missile_guidance_system.lua

function Update(I)
  --Get target info
  target = I:GetTargetInfo(0,0)
  targetPosition = target.AimPointPosition
  targetVelocity = target.Velocity
  
  
  if I:GetNumberOfTargets(0) > 0 then
    for trans = 0, I:GetLuaTransceiverCount()-1 do
      for missile = 0, I:GetLuaControlledMissileCount(trans)-1 do
        --Get current missile info
        currentMissile = I:GetLuaControlledMissileInfo(trans, missile)
        missilePosition = currentMissile.Position
        distanceToTarget = Vector3.Distance(missilePosition, targetPosition)   
        
        --if distanceToTarget == math.huge then
        --distanceToTarget = 10
        --end

        --Guess time until impact
        missileSpeed = Vector3.Magnitude(currentMissile.Velocity)
        if missileSpeed < 1 then missileSpeed = 1 end
        timeGuess = distanceToTarget/missileSpeed
       
        --Setup loop variables
        i = 0
        relativeChange = 1
        timeUntilImpact = timeGuess
        allowedChange = 0.005
		
        --Calculate timeUntilImpact until the relative change in 2 consecutively 
        --calculated times is lower than the minimum value
        while relativeChange > allowedChange do
          --Stop after 25 tries
          if i > 25 then
            timeUntilImpact = timeGuess
            break
          end
		  
          oldTime = time
          --Update expected position with new time
          updatedPosition = targetPosition + (targetVelocity * timeUntilImpact)
		  
          --Update distance to target with new target position
          distanceToTarget = Vector3.Distance(missilePosition, updatedPosition)
		  
          --Update time with new distanceToTarget.
          timeUntilImpact = distanceToTarget/missileSpeed
		  
          --Calculate relative change		  
          relativeChange = math.abs(1-(timeUntilImpact/oldTime))
          i = i+1
        end
        finalPos = targetPosition + (targetVelocity * timeUntilImpact)
        I:SetLuaControlledMissileAimPoint(trans, missile, finalPos.x, finalPos.y, finalPos.z)

        if distanceToTarget < 7.5 then
          I:DetonateLuaControlledMissile(trans, missile)
        end
      end
    end
  end
end