Sky plane calculating

I’m trying to calculate y values for a sky plane, but I’m having some trouble.

The way I see it, if a sky plane is n*n vertices, the vertices that go from one corner to the other should all follow a sin wave. I get a nice half sphere that way if the corners start out at 0 and the center is PI/2. But, obviously the main diagonal vertices aren’t the only ones to consider. I’ve tried something like the following

0 ----> PI/4 -----> 0
|
|
PI/4 -> PI/2 --> PI/4
|
|
0 ----> PI/4 -----> 0

Basically, horizontal movement goes from 0 to PI/4, and vertical movement does the same, but they are summed. What I get looks more like a missle warhead however :stuck_out_tongue: I realize its because 0->PI/4->0 isn’t a smooth curve, but when I imagine a skyplane I imagine less of a curvature along the edges of the plane, where as the diagonal axes have a perfectly circular curvature.

Might someone be able to assist?

Maybe my sky dome implementation will help you with this…
http://cheo.renet.wayne.edu/miguel/