Culling in Ray Tracing pass?

I am trying to use Cesium in unreal with a modified ray tracing pass based on UE4’s RayTracingPrimaryRays pass. The scene is rendered completely with ray tracing. With Cesium, the terrain appears all black until the camera passes within a short distance of the tile. You can see the effect here with the Ray Tracing Debug>PrimaryRays view mode selected in the editor:

Is there a way to render the Cesium terrain at longer distances for the ray tracing primary rays pass in unreal?