Virtual heightfield mesh texutre blurry

Hey everyone,

I met some problems when using virtual heightfield mesh in ue5,
I follow this tutorial on youtube, and all settings are the same Using Virtual Heightfield Mesh For Landscape Displacement In Unreal Engine 5 (Updated) - YouTube

everything goes well until I apply the extra material to the virtual heightfield mesh

without material, the wireframe shows that it already generates displacement


however, the final result looks like a disaster

I am guessing the runtime virtual texture sample is the problem, but not sure where went wrong exactly.
Is there anyone who met the same problem and knew how to solve it? BIG THANKS