The “at camera” landscape actors LOD oscillates between LOD0 to LOD1 in VR/stereo view depending on the distance from the landscape origin it seems).
I have submitted a bug report for this (will link to the issue if/when it is added to the database), but meanwhile am wondering if anyone has encountered this issue before and solved it on their own? My pokes at the source code have yet to result in a usable fix.
Needing to have a large landscape with fast elevation changes and accurate collisions is making this bug quite the headache. The results of the bug being objects visually floating above or clipping or in the case of smaller objects disappearing into the landscape due to render/collision mesh mismatch.
Setting the landscape collision LOD to LOD1 helps, but does not remove the issue. Changing the LOD0 ScreenSize parameter can remedy the closeup issue, but has an unusable perf cost due to the added geometry / bad LOD falloff that make it a no go.
This issue is more severe with world composition and then can then also be observed in flat screen view.
Adding the description of the submitted bug report for a bit more detail:
In stereo mode the landscape LOD calculations don’t work correctly (not talking about the LOD distances being generally 2x as aggressive as flat screen view). The bug manifests itself as the “at camera” landscape LOD oscillating between LOD0 to LOD1 (depending on the distance from the world origin/landscape origin/player start location it seems).
This is problematic due to the rendered landscape and collision LOD levels not lining up (the collision LOD being LOD0 or LOD1) causing objects on the ground to float or clip into the rendered landscape depending on the curvature of the landscape (becomes more obvious with faster changes in elevation)
This is true for at least engine versions 4.27 and 5.2, 5.3, but probably all of them after the landscape LOD system rework.
The bug is present with both instanced stereo and regular stereo rendering settings and deferred and forward shading. A similar, but more severe version of the issue (also shows up in flat screen view) can be seen with world composition being active.
Main testing done with Quest 2 via Oculus Link and Valve Index via SteamVR. The issue is also present in packaged builds (dev or shipping). The issue seems less severe or math works out differently with -emulatestereo launch flag.
Changing the LOD0 ScreenSize setting of the landscape actor can help to a degree, but compromises the performance.
Any input is appreciated!