I have been trying to delveop an algorithm that would be the basis of a voxel-type engine (a.k.a. using a height field). My current strategy is to use a base n-gon and then extend lines from the base n-gon to the heights specified in the height field map. I had hoped to simply take the normal of the base n-gon and then for each point in the n-gon use the formula P=Po + k*normal, (where k = height) to determine the far points in R3 space. My question has to do with perspective projection. Can anyone think of a way that I can perspective project just the base n-gon and then be able to find the far points. What I DON'T want to do is calculate every point across the entire heighfield and then have to perspective project each point. I want to avoid the divide involved in the perspective projection.
I hope this question makes some assemblence of sense as it was more difficult to explain than I had hoped.

-PsyOps