How demos actually work in Rocket League

Although the debates about whether demos are ‘toxic’ or ‘skilled’ have evolved over the years, the constant complaints that demos are somehow broken has never gone away.

Have a quick look on Twitter or Reddit and you’ll soon find ‘demo fail’ clips. Sometimes you’ll even come across pros who will echo this sentiment.

However much people like it, demo-ing remains a fundamental part of Rocket League.

But what really is going on here? Are demos actually broken right now or is it just a misunderstood mechanic.

To answer this question once and for all, I set out to do a full explanation of the mechanic and its rules.

What I thought was going to be a short and easy video quickly turned into a search for answers.

After hours of discussion with programmers and long-time players, along with some custom-made demolition testing tools, I’ve come to some humbling conclusions.

Yes, demos are broken. But not in the way you think. And actually, in some ways, not the way I was thinking either.

Demo Rules

In order to properly assess demos, we have to go back to the rules the developers set out for them.

Now it’s been years since we were given this information, but since they have not mentioned any specific changes to the mechanic, we can only assume that this is still how the game determines if a demo will happen or not.

As stated on a Reddit post back from March 2016, the conditions for a demo are:

1. The hit location must be at the front of the car

2. You must be going supersonic in the forward direction

3. You must be facing within 45 degrees of the surface normal that was hit (angle of incidence)

To get to the bottom of demo fails, we will need to test each rule.

Rule #1: Hit location must be at the front

The first rule ‘The hit location must be at the front of the car‘ is pretty self-explanatory. The front panel of your (hitbox) car is the area that needs to be impacting into the other car.

We’ll cover the exact angle in Rule 3 but, yes, to make it completely clear: it is impossible to demo someone by hitting them with the side or back of your car.

Rule #2: You must be going supersonic

In Rocket League, speed is expressed behind the scenes in terms of ‘Unreal Unit per second’ (uu/s):

  • Supersonic speed (seen when you get wheel trails) is at 2200 uu/s
  • But the actual top speed of your car is 2300 uu/s
  • We should get a demo as long as we are above 2200 uu/s

I used the BakkesMod SciencePlugin by Arator that allows me to see my speed in freeplay and I did not achieve any demos when I was going below supersonic speed. All good so far.

In Rocket League, you maintain your current speed as long as you don’t let go of gas or turn too sharply, meaning you can maintain supersonic without boosting.

However, in the screenshot below, notice how, during turning, my speed drops below the 2200 uu/s mark but I still maintain my supersonic trails for a short period of time.

Are these false trails causing demo fails?

I tested my theory by tapping my reverse trigger so that I dropped below the supersonic threshold. However, I found as long as I still had trails, I was able to get the demo on my target even below supersonic speed. If I slowed down too soon, though, I would lose the trails and not get the demo.

There seemed to be a short period of time after dropping below 2200 uu/s that I would still be considered to be at demoing speed.

Now, this matches with the visual indicator (the wheel trails) so I didn’t consider this a major mechanic problem but it is something I had never even heard of before.

Curious, I took the info to a well known Rocket League Modder named Cinderblock. He was able to find the specific code in the game.

It seems like there is a turnoff speed buffer of 100 uu/s which means that, as long as you don’t drop more than 100 uu/s out of supersonic, you would still get a supersonic buffer time of one second.

This means a player going for a demo could easily drop out of 2200 uu/s but have the trails right up until impact, creating a frustrating no-demo moment that’s hard to understand while at game speed.

Conclusion: Rule #2

To clarify, I was able to prove if you have trails you get the demo (as long as the non-speed related requirements are met of course). It is not the case that you can demo without trails showing.

In the end, when it comes to the “must be supersonic” rule, we do have to accept that the mechanic is working as intended. However, with the buffer, it does mean we can get lower speed demos.

As a point of clarification: dodges add instantaneous speed as shown in the clip above. Supersonic is when the speedometer turns yellow. This can make it seem like you get a low-speed demo because at game speed there will be no observable trails.

Rule #3: You must be facing within 45 degrees

If only demos were as simple as: be supersonic, get a demo.

The ‘angle of incidence’ is probably the most misunderstood part of the demo mechanic, assuming a player even knows about it at all.

Demos were not intended to be given for side-swipes or glancing blows. Instead, a cone representing 45 degrees from the surface normal was how demos used to work.

I say ‘used to’ because those angles have been broken for a long time.

Reddit User and Coach Horary Hellfire was the first person to bring this problem to light over a year ago by going back and comparing demo situations with earlier versions of the game.

He eventually traced the issue back to version 1.43, meaning demos have actually been easier since Mid-Season 7.

Why were angle calculations sometimes working and sometimes not? To test this fully, I employed a member of the RLbot community named Skyborg.

What was oddest about our findings was that it was not just the angle of incidence that mattered to demo-ing but the location of the angle of incidence.

We tested and found the following results as of March 2020:

Centre of car impact pointNear side of car impact pointFar side of car impact point
Aim for the middle of the sideAim for the back of the sideAim for the front of the side
Demo possible from 10° to 170°Demo possible from 10° to 170°Demo possible from 40° to 140°

Example of far side impact point (aiming for the front of the side) which results in no demo.

To confirm these tests, Horary ran some personal tests outside the bot environment which resulted in the same outcomes.

Location, Location, Location

On paper, I was okay with a widened range of demo angles. But what doesn’t make sense is why you have different results depending on the impact point on the hitbox.

I can see why this would be confusing for players as an angle that usually gives you a demo suddenly doesn’t just because you hit past the centre of mass.

In a recent Twitter exchange, Corey from Psyonix replied to clarify in a little more detail:

This graphic might help to clarify why centre of mass is important for demo-ing:

Looking for a Fix

So is there a fix I would recommend here?

Well, it depends. If we go back to the old 45-degree rule, I think the ‘demo fail’ complaints would sky-rocket.

Personally, I am in favour of the wider demo angles but it needs to be repeatable no matter where you strike the hitbox.

If you want to watch the full video with all my testing footage, check it out here.

Edit: Since this article was written, Psyonix made an update (v1.78) to Rocket League, specifically looking at Bumps & Demos, so I made a video covering what the changes meant:

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