4Game

Preface: I love DotA because every little, tiny thing matters. Every decision or optimization you've made could be the difference between winning and losing. While 2.75 milliseconds does not sound like a lot of time, I'll explain why/how it can make all the difference… but Valve will apparently be removing OpenGL support from the game soon.

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There are 2 main purposes for this post:

• Let DotA players know that they'll likely see performance increases by switching from DirectX 11 to OpenGL
• Let game developers (Valve in particular) know that if they care about their game's responsiveness, they need to use OpenGL.

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Overview: Using OpenGL saves me an average of ~2.75 ms of system latency PER FRAME (despite an average lower frame rate of ~14 fps) when compared to DirectX 11.

A difference of as little as 3 milliseconds can equate to increases in accuracy of up to 10%. "But… how does so little time amount to such a large difference?" That ~3 millisecond time is on a PER FRAME basis, and there is a compound effect on your ability to react from receiving each frame "late".

Nvidia has shown that a difference in 8 milliseconds can lower average Times to Kill (TTKs) by 12% (on average) in games like CS:GO and Valorant (From 1.53 seconds to 1.35 seconds) (So 8 millseconds per frame can equate to 180 millisecond faster kill times over a ~1.5 second period?? Yes.)

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As a Clockwerk spammer, here's what lower system latency means for me:

• I catch enemies in Cogs more often when running them down early game.
• I can hit Blademail before being dueled by LC or hit by Lion finger more often.
• Hooks are more accurate & require less prediction.

Test Method:

I built a new tool to measure system latency. The methods used are very comparable to Nvidia's new Reflex Latency Analyzer technology, and if the mods allow it I'll post the website where I am attempting to sell the tool with more info here.

If there's enough interest I'll make an in-depth video discussing the tests and results.

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Data:

I can share a spreadsheet of the data gathered used to make this post if there's any interest, but apparently OneDrive links can be caught by Reddit's filter and make your post hidden…

System Specs:

• Processor: Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz, 3408 Mhz, 4 Core(s), 4 Logical Processor(s)
• Motherboard: MSI Z270 SLI PLUS (MS-7A59)
• Operating System: Windows 10
• RAM: 16.0 GB RAM
• Graphics Card: Nvidia GeForce GTX 1060 3GB

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FAQ

"But Skew! …Battle(Non)Sense showed a couple of years ago that capping your framerate can help reduce your system latency in many AAA games."

Yes, I'm aware of that. I also ran tests capping the framerate to 100, 120, 140, and 160 using both rendering methods(DX11 and OpenGL) and both the in-game frame rate limiter in addition to RTSS. None of these methods showed any obvious, significant change.

What about Vulkan?

Tested briefly, but did not see any meaningful change.

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Conclusions:

I really want Valve to consider this data before they completely remove OpenGL support from the game. I believe OpenGL is strictly faster than DX11 for end-to-end system latency and higher responsiveness in DotA 2. I could literally talk about system latency non-stop, so for brevity I've left quite a bit of info out of this post. If you have any questions, please let me know. Go change the setting, restart your game and give it a shot, and then let me know how it feels. If you start landing more last hits or spells more accurately, that's almost certainly attributable to a decrease in system latency.

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TL;DR: I have found that OpenGL is, on average, 2.75 ms faster (per frame!!) than DX11 for my PC and Valve is removing OpenGL support. You should try out OpenGL and let Valve know if you see performance improvements. It may help you land more last hits, more hooks, and generally have quicker reaction times. These results are machine specific so YMMV.

If the devs want to stick with their decision of discontinuing support of OpenGL in Dota that's fine by me, but I just want to make sure they're making that decision with all available data.