Semi-correct normals. I haven't figured out how best to compensate for the modifications I make in the vertex shader. Its a bit of trickery and a bit of luck.

oh yes. I know that problem. as far as I can tell there is actually no way to get correct normals other than a normal map if you do the transformations on the vertex shader but:

Why don't you transform the landscape on the CPU, that should be very fast too if you use vertex arrays instead of VBOs or if you set your VBO to gl_stream_draw.

Or is it only the vortex effect that happens on the GPU?

Well, Moka, frankly I am just stabbing in the dark here. I know I wanted to learn more about VBOs and I wanted to do more with shaders. I had no other plans. I dont know what gl_stream_draw is or how it might be useful. I will google it.