Dynamic Scalability to maintain 75hz?

Development Platform & Builds XR Development
1

I’m currently working on a demo that has only static geometry without moving parts (aside from the occasional door)
Though i’m looking for a way to dynamically degrade settings depending on how complex the scene is (and if the camera/user is moving/rotating/translating), just so “any” computer can run the demo without judder/fps problems.

I thought about comparing values every frame to get delta values of the fps and rotation/translation of the headset and then triggering progressively aggressive feature reductions to maintain framerate while moving, and then when there is no motion detected enable more complex features to create a more beautiful image. Similar to what you see on forward render engines.

However, just the frame rate check every tick knocks off about 5 to 10 fps alone, so its actually worsening performance.
Is there a way to dynamically scale features/frame rates depending on if there is a need for them?

A similar degradation with a custom engine you can view here: http://depot.floored.com/scenes/Panoramic-Interests_The-Panoramic_Micro-Studio notice that when you move/rotate/translate it renders out to a much smaller frame until the translation/rotation stops.

2

How are you checking the frame rate?

In theory it should just be 1 / delta time, which should not affect performance at all

3

yes i’m checking using the delta time in the Tick event, so its listing the delta time of each individual frame

4

That causes framerate issues?

It really should not.

You could try using the profiler and noting what specifically causes the frame time difference between not checking the framerate and checking it

5

Is it the tick event delta check that’s expensive, or actually toggling on/off certain features?

If it’s the feature toggling that’s consuming time, you might consider adjusting “hmd sp” on the fly instead (or at least as a first step), as the change is very cheap (it’s already part of the Oculus frame buffer distortion), and more progressive / less noticeable (it changes gradually, versus just on/off).

See this excellent talk by Tom Forsyth at Oculus Connect, particularly the segment starting around 50 minutes where he discusses using this technique on the fly](https://www.youtube.com/watch?v=addUnJpjjv4#t=2993):

6

hmm thanks for that!
Thats an interesting video :wink:
I now have a few settings that trigger automatically as soon as a HMD is detected when going fullscreen