terça-feira, 18 de outubro de 2011

Lerp in Left 4 Dead

What's Lerp?

Lerp or interpolation is nothing more than an artifice used by the game's engine to make the game run "beautiful" and smooth. It avoids the infected/SI to walk/run stuck, fading in and out, even under packet loss situations.
That works pretty fine, but the question is that it's also "slows" you. The stardart lerp value is 0.100, that means that when you're on a ping of 100 and with 0.100 lerp, actually you'd be on a 200 final ping.

The standard lerp value of 0.100 will work fine when you're playing coop, since the AI hunters and jockeys will spawn early and with their noises you'll be ready by the time they'll try to pounce you.
But under a competitive mode, your opponent will just spawn a few seconds before attacking and probably from a spot you're not specting. Understand why a low lerp value is so important



The first picture shows a pounce seen from a 0.100 lerp. Notice to the hunter's hitboxes are in fact on the ground, while the animation still shows him in the air. That means; you must deadstop/skeet him really really early or it'll be too late.





This one shows the hunter from a 0.016 lerp, one of the most used values by PRO players.

Notice in this one the hitboxes are almost "inside" the hunter's animation. that gives you the chance to quick react under surprising situations. Chance that you probably wouldn't have with the 0.100 value.



When you see someone else killing a charger with a single melee/cutting the smoker's tongue, surely he's using a low lerp value.

Ok, now you already understood about the lerp, let's learn how to set it up.



Setting up the lerp values 

To change the lerp, use the command: cl_interp
For a 0.016 lerp, make use of cl_interp 0.016 (Standard value: 0.100)
Don't forget to low your ratio value, because it will limit how low can you set your lerp: cl_interp_ratio 0 (Standard value: 2)

Other values you also should change are:
cl_cmdrate 100
cl_updaterate 100 




If your connection is unstable, i wouldn't recommend you to change the ratio value, since it determinates how many extra updates you'll receive from the server. That means, if you lose a packet just before a pounce, you'll see yourself pounced for sure next update.