Terrain Engine in D3D

Procedural terrains are possible. There's a sample on Robert Dunlop's homepage that does fitting with catmull-rom splines (I think) in the shader (it's likely to be in his scrapyard).

I don't know about D3D's high-order primitives, but you have some D3DX helpers for splines that might be of use.

Is your question about a function that will create a grid of spaced vertices for you, allowing you to provide the spacing value? I don't believe so. That's fairly easy to write mathematically though.

However, for height issues, there are a lot of examples on height maps, which you may find to be a valid solution to your problem. You can also find information on perlin noise, midpoint displacement, and other fractal algorithms capable of randomly creating terrain heights. Once you have that under your belt, you can look into geomipmapping and ROAM algorithms for displaying your terrain efficiently.

Good luck,
Chris

If you have a grid of points, but much less detailed ie further apart than currently, you can use those points to build a curved surface for each 3x3(I think) subsection of the grid.

How can i use those points to build a curved surface for each 3x3 subsection of the grid.Please,tell me where can i get working examples on it? or on High Order Primitives.Thanks.