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DotA : a question of time

by François Rioult last modified 2008-05-14 19:38

I study in this article the behavior of the frontline between DotA's teams. This issue is not discussed in the forums, but it can be used as an important strategic  topic. I show how to analyse the frontline, the possible actions and their result.

Introduction

Predicting the frontline progression during a DotA game is not always easy. It namely does not depend on the opposing forces : a frontline between 4 Sentinel creeps and 2 Scourge creeps does not necessarily to Scourge. Also ennemy creeps in our territory does not mean thait it is endangered.

Answer the two following questions is not obvious :

  1. should I go help my creeps, is my tower endangered ?
  2. Should I help my creeps pushing the lane ?
I try here to give indications for answering these questions. In that purpose, I have been observing and noting the position of the front between the two base towers. After recalling some DotA mechanics and defining some mesurement tools, I conclude that watching the temporal variation of the frontline between two creeps generation can help in predicting its advance and is an important strategic aspect.

Temporal characteristics of DotA Lanes

The frontline progression should use a distance measure. It is however hard to precisely measure in DotA, unless with the help of a reference map. That's why i will be using here some time measures. I first recall some constants that can be used to transform time to distance. These constants reveal differents behaviors between middle and external lanes.

The towers are denoted this way :
numero

Creeps spawn every 30 secondes. Middle creeps take 36 secondes to reach the ennemy base, external creeps need 57 secondes. The below images show the progression times for Sentinel and Scourge.

sentinelscourge

These elements are important when comparing to spawn times :
  • for the middle lane, agressors come at 36s or 66s and defenders are generated at 30s or 60s, namely 6 secondes before the theoretical instant when agressors could attack the tower. It means that there always are creeps for defending the tower before it is attacked. It is hard for creeps to alone push in the middle lane, because it has a certain self-defence skill.
  • for the external lanes, agressors come at 57s or 97s and defenders are generated 3 secondes after : there exists a non negligeable time for attacking the tower. Without any hero, a creeps group is dangerous in the external lanes and can hurt the base.
Another strength (or weakness) of external lanes is that they require 30 secondes more than for the middle lane to reach the base, so one more creeps spawn can be on it. On external lanes, creeps groups can be bigger, say 4 ou 5 generations, than on middle lane, where there are never more than 3 generations.

I'm really convinced that these details are not due to fortune and belong to DotA balancing.

Let's remark that the towers 14, 25 can be viewed as a virtual spawn point, as well as 22 and 33 for Scourge.

The frontline


The frontline in DotA is essential. It is drawn by the three front points between creeps. The progression of this line is crucial for controling the game. It gives multiple strategic factors :
  • the control of the ennemy territory. When the front is on the river, it is neutral. In other cases, the front is progressing in one territory.
  • the independant progression (without hero). Is the front progressing to ennemies, going foward under assaults ?
  • the hero positions. In general, they are behing the frontline, but they can be gangers or neutral farmes.
  • the potential risk of pushing the front. One should be informed that the front line can rapidily change.

The neutral territory is at equal distance between the accessible towers. Every team should tend to keep the river as neutral territory, namely balancing towers. It is absurd for exemple for Sentinel to push the tower 14 while 33 and 32 are destroyed and 34 stills forbids Scourge's territory. In this case, Scourge's creeps are always by Sentinel et require a constant attention. The neutral point is too far in Sentinel and the tower 34 has to be pushed.

To see how to control the frontline, his behavior without heroes has to be explained. Then heroes bring some strategic actions.

Measuring the frontline progression


The following informations come from a test game when I use Lich to destroy the towers 32, 33, 34, and 35 and set a balance at the neutral point. This study has been done in particular conditions, because no hero is active (execpt at the end), and creeps blocking, creeps-control skill or items obviously change the results.

A simple and precise measure of the frontline consists in notting the time when each creeps spawn come to fight. The following charts show the progression of the frontline in the bottom lane. 0s is the neutal point, around 30s away from towers 31 and 36. The X-axis tells the generation index, each generation is a point on the curve (Sentinel is red, Scourge is green).

The first chart tells time gap relatively to the neutral point in front if the tower 33. The horizontal line show the position of the towers (32 to 35 are destroyed). The second chart shows the frontline speed, measured by the front gap between two generations.

graphe.jpg
grapheDiff.jpg

The history of this game is :
  1. Scourge pushes from the neutral point to the tower 31 in 4 generations. Since the initial instant, the frontline speed increases quickly until 13 secondes/generation.
  2. after a short balance arout the tower 32, the front goes to Scourge and reaches it with 8 generations. The speed goes to 17secondes/generation
  3. after a long balance (between generation 13 and 23), the front walks to Sentinel and reaches it with 8 generation, then Scourge at generation 45, then Sentinel at 55. During each progression, the speed goes to 13-17 secondes/generation.
  4. the last stage is special. With Lich I kill all Scourge creeps and push with mine. I manage to push the frontline between the tower 31 and 36 with only 3 creeps generations. The speed reaches its maximum with 35 secondes/generation.
  
One notes three classical frontline behaviors :
  1. balance : the progression speed is slow, under 3 s/gen. The frontline does not really progress, but this state is not stable and the lane will take a random direction by increasing its speed.
  2. independant push : creeps walk alone with a speed quickly going to 13-17 s/gen. This push needs 8 generations (4 minutes) to go from one base to the other.
  3. hero push : one hero helps its creeps in the push. The speed grows very fast to 30 s/gen and the total push of an lane requires only 3 generations (1.5 minutes).

Strategy : act on the lanes

During a real game, the frontline speed enables to analyse, predict and verily control the frontline progression. An estimation of its time evolution between two generation is sufficient. Depending on its value, one hero can use three different strategies :
  1. push : help the creeps pushing
  2. defend : only killing creeps without go forward
  3. deny : destroy his own creeps to make enemy progression easier.
In the three cases, one can increase the frontline progression, stabilitate it or slow it. These actions are important for the strategic control of the frontline.

Balanced Points

equilibreOn specific points of the map, a natural balancing can appear, if creeps forces are equal. This front point will slowly vibrate, then choose a random direction. The balanced points are :
  • for the middle lane, they are in the river or behind the towers 21 and 26.
  • for the external lanes, the are also located behin the -1 and -6 towers and at 15s, 30s, and 35s.
This means that creeps can not be balanced out of these points. If a front point is out of these point, it is necessarily progressing. Its speed as to be evaluated before taking a strategical decision.

Conclusion

By analysing some DotA mechanics, we can learn that the three lanes should not be unthinking considered. The middle lane has a certain self-defence skill and requires less attention. The long way of external lanes allows them to host more creeps and the frontline progresses fast. These lanes have to be more focused because they represent a usually ignored threat.

Measuring the frontline speed is easily done by watching the gap between two generations. A slow lane can be balanced, otherwise it walks forward and will not stop before a tower.

The answers to the two beginning questions are :
  1. should I go help my creeps in my territory ? Is my tower endangered ?
    If the frontline move backwards, it menaces my tower and I should go defend. If the front line goes forwards, the answer depends on the following question.
  2. should I help my greeps in progressing in the lane ?
    If I want to set a balance, it is a good idea. This lane will not have to be watched in the next minutes (up to 4 minutes quiet). In this case one should not kill too many ennemy creeps, otherwise the frontline will progress very fast to the ennemy, may be too fast ?
Be aware about the frontline speed is relevant and allows a strategic control of the lanes. The time in DotA provides useful information about the lane progression that lead to essential gameplay actions.
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