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Unity fixed update rate problem


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I'm not sure if this is the right place to ask this question (I posted it on the Unity site as well), but I'm a Vive developer and I need support, so that brought me to this forum 🙂


I am developing a baseball application for the HTC Vive using SteamVR. Since a lot of people have difficulty hitting the ball I wanted to try and change the fixed update rate to see if that made it better. So I made a script that allows me to change Time.fixedDeltaTime and display the value on screen.
I know that SteamVR by default locks the fixed update rate to its display framerate (90 fps, Time.fixedDeltaTime=0.0111111), so I added the [SteamVR] prefab to my scene and set the checkbox that controls this locking to false. Made a build and tested it and it seems to work. I have the feeling I get better results at smaller fixedDeltaTime values. But then I tried it as well in the editor and there the confusion set in.
In the editor the checkbox in [SteamVR] was set to true at runtime, even though I had set it to false at design time. I modified my script to show the value  that the script sees and it showed False. So the editor does not represent the situation in code. Also, the fixedDeltaTime value in project settings is still 0.011111, even though my scene is running and on screen I see a different value (0.004, 250 fps).
To make it even worse, I tried the same for my tennis app, which is still running on Unity 2017 (the baseball app is Unity 2019). And guess what, in Unity 2017 the editor checkbox is false and the project settings show the same fixedDeltaTime as on screen!
So I hope someone can explain why this happens and reassure me that the values in the code are the correct ones. Thanks!
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  • 3 months later...

I found out that the [ViveInputUtility] prefab has its own Lock Physics Update Rate flag. I need to set both to false to be able to modify the framerate. 

So the issue is solved, but I find it strange that VIU has its own flag and does not use the SteamVR flag.

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