Normals problem

This something you can set in DirectX whether is uses CCW or CW. I think CCW is the common one. So if you set of points use both, you need to fix that. Also once you have then all corrected the normal (or simple triangle normal) can be calculated using just 2 of the vectors the make up the triangles edges

normal = (v1 - v2) cross (v2 - v3);

I believe that will do it for CCW, you can see how this would be reversed for CW, but rather than thinking if I'm rock there do it the other way, in which you (v2 - v3) corss (v1 - v2). Crossing creates a vector perpendicular to the plain the triangle creates.

Also if you want you set Directx to not backface cull. Which is what you are looking for. If you set to no lighting or full ambient lighting and set to no backface culling both sides of the triangle will be rendered.

Well, I think you should just fix your file to get every triangle defined in a fixed way, be it CW or CCW. If you don't take this step you'll find it almost impossible to do a correct culling, and believe me, you'll need it sooner or later... When you have an "ordered" file, than you can calculate the normal for the triangle with the forumlas posted by jimmynelson...
Always remember, a good data structure is the best way to optimize your code...

One step further: if you have to use Gourad Shading, you'll need a normal for each vertex. To get the normal for a vertex, add up the normal of EVERY triangle sharing that vertex, and then normalize the resulting vector. Simple, hu?

Greetz

I know that if i can fix the vertex source i solve my problems, but I can't do that since I'm importing data from another program and the amount of vertex to check and fix is really huge and can't be done by hand.

I need an algorithm!!, but even if i tought on it for a long, i can't find one.
That's why i was thinking to solve using pixelshader.

using full ambient light instead, give bad detailed scene...