Junglel flickering

(Porthos Woofs ODZ (D)) #1

Zwift did an update today Oct 10 (9 pm PST start up).

Without my changing any settings on my Winblows 10 PC the graphics seemed much improved. The dynamic range was much better. Saturation was deeper. Colors popped more. Highlights and shadow detail both much improved from past.

However, riding through the jungle in the dim light (some if near night, other times not night) the rendered scene (entire scene) would flicker from dark to light. More dark than light. It STOPPED this behavior when I left the jungle in spite of being in the dark shadow of the mountains. It seemed ONLY to be in the Jungle. I also seemed to be when the scene was darker in the Jungle that the rendering could not decide if it was really dark or light. When there was strong light out in the open, it was OK.

(Mike Kelly) #2

I have seen this for the past year or so as well. Interestingly I just finished a ride through the jungle after the update yesterday and I am not seeing the issue now. I believe the jungle is probably the most graphically demanding course on Zwift. I run in 4K ultra with an i7-3770 and a GTX 1060, which squeaks out 60 FPS on most of the courses, but I see a lot of FPS drops to as low as 49 FPS as I go though the jungle. I’m not a gamer or a gaming programmer, but my guess is that every graphic element of the course gets assigned a rendering priority depending on how close it is, how fast it is moving, how big it is, etc. Then the GPU decides for a given frame what it is going to have time to render and in how much detail before it is time to send it to the screen and move on to the next frame. I am also guessing that ambient light changes are in that priority mix as well. With my hardware being at the very bottom of what should be used for 4K, I am not surprised to see issues like this. Although there may be some tuning that Zwift could do to optimize rendering priority, it is probably more a matter of using the right settings for the hardware that you are using. I have no idea if this is similar to your situation, but I’m just throwing some ideas out there. I would be interested in hearing from others with this kind of experience.

(Porthos Woofs ODZ (D)) #3

This was with Zwift with a pretty beefy gaming rig (1080 Ti), and I can run games like Farcry 5, Ghost Recon, Warframe and the like at top end settings with no problem at 1920x1080.

I don’t ever see any frame rate type problems (I am not monitoring it quantitatively, however).

I have a background in coding and game design from the late 80s onwards, but I have only done modern “AAA” work in UR4 and not used any other engines.

So, I do not have enough expertise to come up with an explanation why the scene lighting would flicker as it did. When I overload my own work with too many actors/lighting etc. what I see is an overall frame rate drop and/or processing delay in getting all the actors moving (I do push it sometimes). I have never seen such a thing as when the scene flickers. That is only in UR4, however.


The Junge is HANDS DOWN the most glorious Zwift region with the 3D aspect of the trees as one rides through them - not to mention the overall atmosphere and ambiance.

One thing I learned long ago as a game designer is that you want to design for the state of the art hardware because by the time you have all the bugs worked out and your project published that “state of the art” will already be getting obsolete.

Way back in the end of the 80s and early 90s I spent a huge effort to make my game software (K-12 learning games) run on the old Macs (I had customers in convents who only had old tech). It was quite a bit of work, and of course when it was all finished most of those customers had already upgraded their hardware to the new fangled color displays! Oops.

(Mike Kelly) #4

You have an interesting background. I would agree that you shouldn’t be seeing that type of performance with your setup. I also found it suspect that as I made the turn into the jungle that the ambient light would tend to “overshoot” where I thought it should change to and flash 2 or 3 times before ending up at the right point for the scene. If you don’t get any additional suggestions from the forum, I would recommend filing a support ticket at zwift.com. They are very responsive, and the game’s log files seem to be quite verbose for them to investigate. They have worked with me on several issues were able to get to the root cause quickly. Good luck!