Terrain z-flicker , how ?

I draw a mesh on the terrain, every vertex is on the terrain surface, then i set the mesh's polygon offset like this:

depth_bias 1

but with the ETM, when camera near the mesh, it will flicker:








i test one mesh on the other mesh, no flicker, but on the ETM, the flicker happed, why ?

Potentially a LOD issue, even though the flat part shouldn't be affected. Still, try setting maxPixelError to 0.
Also, you should probably place the mesh itself slightly above the terrain.