First Look: Pack Dynamics 3.0 on Zwift

September 7, 2021

LAST UPDATED September 7, 2021

We haven’t heard much from Zwift Co-Founder Jon Mayfield lately, as public interactions on game updates are now being handled by other members of the Game Team, including Wes Salmon.

But Jon and his team have been busy, working on various projects deep in the bowels of Zwift’s super-secret R&D lair. (Actually, thanks to Covid, I would guess they’re all working from their homes. But the lair sounds much cooler.)

One project recently pushed out to the live codebase is Pack Dynamics 3.0 (we’ll call it PD3 for short). I’ve had the opportunity to participate in a few test rides using PD3, and wanted to give you all a look at what’s coming. Because it’s exciting!

First: The Current Situation

While most Zwifters have grown used to the game’s pack dynamics, the way our avatars move on the road lacks realism in various ways. Watch a snippet of a recent race and see how the pack looks to you:

See anything odd?

I see a lot of side-to-side movement within a tight pack, which isn’t something that happens IRL. Outdoors, riders hold their lines pretty well in a group, because there’s not much space to move right or left, and it’s a dangerous move if overlapping wheels are involved.

I also see the bodies of riders moving through other riders, which of course knocks the realism down a notch.

Lastly, I’d say the pack looks too tight. Even a pro peloton can’t fit that many riders into a tight space!

PD3 seems to address all of these issues quite nicely.

See Pack Dynamics 3.0 In Action

Zwiftcast creator Simon Schofield participated in the same two test rides as I did, and put together a quick video with his impressions of PD3. I think he sums it up quite nicely:

Less Lateral Movement

You’ll notice the jerky side-to-side movements visible in my race video are nearly non-existent in PD3. It feels and looks much more realistic… like the pack is a school of fishes rather than a scurry of squirrels.

Less Sticky Draft

While Zwifters generally recognize why the sticky draft exists, there’s also nearly universal disdain for it. We like sticky draft when it helps us hold a wheel, but we also hate feeling like it’s harder to get around another rider than it should be.

I found the draft to feel much more natural and not sticky at all in PD3. I could ride up behind a rider and hold my position on their back wheel by modulating my power. And if I wanted to go around them, bumping up my power moved me smoothly around, without feeling like I was wasting watts trying to power out of the sticky draft.

One caveat, though: both of the test rides I’ve done were at a rather low pace (2-2.5 w/kg). It may feel quite different at race pace.

More Realistic

Overall, the look of the pack, and the feel of moving forward and backward in it, is much more realistic with PD3. Riders hold their lines well, and, at least in the two test rides I’ve done, there is more space between riders.

Will the increased space making drafting more of a challenge, especially when it matters at high speeds in races? That remains to be seen because, again, we haven’t tested PD3 in a race situation.

Better Predictive Positioning

PD3 also includes an upgrade that isn’t apparent to the individual rider, but matters a lot when it comes to racing and broadcasting. That is much improved predictive positioning of other riders.

The positions of other riders on your screen are calculated using a combination of client-side predictive positioning (your Zwift software is predicting where each rider is going, and rendering their positions accordingly on your screen) and server-side adjustments, where rider positions are broadcast to a central server then your game client sees them and adjusts riders positions on your screen.

This means that one Zwifter’s view of the pack could be quite different from another Zwifter’s, especially if server connectivity was slow or poor. Most of the time this doesn’t really matter – but when it comes to racing, and especially pack sprints, it matters a lot!

In the past few years, Zwift has been tightening up how well this works, so rider positions have become more and more uniform between Zwifters. But PD3 tightens this up much more.

When Will It Be Released?

Zwift is being cautious in rolling out PD3, and will continue running test events before a global PD3 rollout. The current PD3 has a few bugs which will be fixed before any larger public release, and a lot more private testing will take place before public test events are available.

The broad release plan is: