(so heightmap.bmp must be 640*640 pixels?)
I think you should not use EntityOrder 10, nor should you render both. Instead I'd try to use EntityAutofade with both, or if this doesn't work I'd implement a by-vertex entityautofade, based on vertex distance and Vertex Alpha. (altering only vertices alpha that are overlapping detail/LOD areas, noless make sure it's not a bottleneck).
Basicly I'd suggest to cut huge meshes in pieces. A huge heightmap of say 2560*2560 may render very fast when you make it a grid of individual mesh patches, each one of a few thousand tris.
Have a look at the ClusterizeMesh sample in the archives.
I think you should not use EntityOrder 10, nor should you render both. Instead I'd try to use EntityAutofade with both, or if this doesn't work I'd implement a by-vertex entityautofade, based on vertex distance and Vertex Alpha. (altering only vertices alpha that are overlapping detail/LOD areas, noless make sure it's not a bottleneck).
Basicly I'd suggest to cut huge meshes in pieces. A huge heightmap of say 2560*2560 may render very fast when you make it a grid of individual mesh patches, each one of a few thousand tris.
Have a look at the ClusterizeMesh sample in the archives.