Well, my poor English can not describe it properly so I've attached an image which demonstrates one subdivision rendered in full and in low quality. Inside soure code (gl_terrain.pas) also is included (but commented out) a lower resolution without the surrounding quads (15x4 = 60 triangles). The pivot of the triangle fun has the higher z value of the subdivision, I was about to make x and y of the pivot point to the higher's z point x and y but I thing I've left it to the center (it just looked good that way and I just left it...).
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