This issue became apparent after updating 4.14.0 to 4.14.1.
1.Make a new project
2.Make a blueprint class, and add a SceneCaptureComponent2d
3.Make a new RenderTargetTexture and assign it to the component
4.Place the blueprint actor in the level, and hit VR Preview
It instantly drops to 45 fps (reprojecting).
Here’s a screenshot of the GPU Visualizer: Screenshot - a98913db213b1095750fdd25b8c24d19 - Gyazo
The same setup does not cause this issue in earlier versions of the engine.
EDIT: I also tried packaging a Dev build after reading about HZB occlusion issues when PIE. The same results occur when playing a packaged build.
EDIT: This only happens when using Vive and SteamVR. The Rift does not have the same issue.