[osg-users] Oculus+OSG

[Björn Blissing]

Jan Ciger wrote:
> That blog post I remember, but the conclusion there seems to be that positional timewarp introduces occlusion artifacts and a lot of extra complexity. I didn't sound like something they are intending to implement at the time.
> 


Hi Jan,

One reddit user made two short videos to display the effect of positional timewarp. Both a normal case and one extreme case (pushed to fail).

In the first video the frame rate is artificially dropped. Then he toggles between positional timewarp on/off, to show how this trick can alleviate a frame rate drop and still do some minor movement without stutter:
http://zippy.gfycat.com/JealousMeagerKestrel.webm

The second video shows what happens if you move to much. Here rendering is frozen and the HMD user continues to move until the effect fails miserably:
http://giant.gfycat.com/AgileThatGraysquirrel.webm

The author wrote the following description:
"Timewarp is a way of distorting the image the HMD receives in the event that the simulation can't keep up with the target frame rate or refresh rate of the device in order to compensate. So, motion-to-photon latency and headtracking will appear to remain consistent, even if your framerate is fluctuating. This helps to alleviate jitter. This, however, was only previously possible for rotational tracking in a prior Oculus SDK. Now the distortion is possible for positional tracking as well. Both have their limits of course -- you can only move so much before the scene becomes terribly warped. It's meant to cover for momentary or tiny dips in frame rate -- not for massive ones that last a while. "

Best regards
Björn

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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=65056#65056