here''s your height map:

1 2 3
4 5 6
7 8 9

triangle 1: 1 - 2 - 4
triangle 2: 4 - 2 - 5

Here I defined the triangles for the upper left 4 points. Do the same thing for all points in the heightfield, and u''ll be all set.

I was just where you were awhile ago, so maybe I can help. First, what I suggest, is to sit down with a piece of paper and draw triangles for each dot. Then look for patterns If you can get it, great, otherwise, I''ll tell you...right now.

The first thing you need to realize is that you''re going to have to write code for making two types of triangles, kind of. You''ll have the front facing, and the back facing (if this doesn''t make sense, don''t worry--you''ll see what I mean). Observe.

You''ll have a triangle like this:
/\
/_\
And a triangle like this:
__
\ /
\/

Now, in order to make the mesh, you make a series of for loops, and count the triangles that you''ll need, like so.

int Count = 0;

for(int i = 0; i < Height - 1; i++)
{
for(int j = 0; j < Width - 1; j++)
{
Count++; //2 triangles for every pass.
Count++;
}
}

Then, you allocate enough memory for this Count many triangles, via malloc,new, or whatever. You then actually make the triangles, like this:

in Cnt = 0; //used to track which face we''re on.

//Now we initialize those triangles.
for(i = 0; i < Height - 1; i++)
{
for(int j = 0; j < Width - 1; j++)
{
Faces[Cnt].Verts[0] = (i * Width) + j;
Faces[Cnt].Verts[1] = (i * Width) + j + Width;
Faces[Cnt].Verts[2] = (i * Width) + j + 1;
Cnt++;

Faces[Cnt].Verts[0] = (i * Width) + j + 1;
Faces[Cnt].Verts[1] = (i * Width) + j + Width;
Faces[Cnt].Verts[2] = (i * Width) + j + Width + 1;
Cnt++;
}
}
A thing to note would be that the Face class contains integers for which vertices belong to it. You can easily use pointers or whatever, or take the vertices that you made in your dot thing, and set them to it. So, the code works, but it looks ugly (that is, it sucks without tabs and colors--I wasn''t refering to the code, because I code so beatifully...). I hope that it helps you out.

This by far is the easiest part of rendering your terrain. Suppose your grid is 256 by 256, and you want to render triangles out of it. your points would range from 0..255 in both directions.
so we have a loop like this :
for (y=0; y<255; y++)
for (x=0; x<255; x++)
{
// We will use rectangular indexing coordinates,
// so you know which coordinates I am referring to
draw3triangle( height[x,y], height[x+1,y], height[x+1,y+1] );
draw3triangle( height[x,y], height[x+1,y+1], height[x,y+1] );
}

That is all, if you still don''t understand, then I don''t know how else to put it.