if you've got inverted faces that weren't originally inverted untill you imported then you need to fix them. telling everything to render two sided will only work within 3ds max, but once you export and try to use it in a game it will mess with the lighting/shading.
if its for a treee or whatever, you should be fine then they usually only use flat one sided planes anyways. but if say you have complex geometry where one or two faces on inverted you can:
apply a "normal" modifier to the mesh and make sure "invert normals" is checked. from here you should now see the majority of your mesh being inverted, and those few faces that were inverted before now showup fine, this simply will make it easier to see and select your inverted polys. collapse your modifier stack, right-click, convert to editable poly, use the polygon selection tool, then select the faces that you want to fix, then under the "edit polygons" tab and with your polygons you want to fix selected hit "flip". now, apply the "normal" modifier again and once again make sure "invert normals" is checked, collapse your modifier stack again and you're done. now everything should be facing the right direction.

Quote:Original post by tehExploited
Thx guys, that sure helped. Now, I have another question and I don't think it is worth another topic. Basicly I got a map now, but I'd like to have lightmaps in it and have 3d max store the texture coordinates. Now I heard this process is called lightmap baking but strange enough I can't find the right information on google.

yeah, you somehow bake the global illumination render data into maps. however all engines i've dealt with have been modern that require no lightmaps, however i'll take a guess and say its a render to texture function in 3ds max.
startup 3ds max, select your uv unwrapped mesh, and press 0. now from here i am assuming you'll have to switch over to the "mental.ray.no.gi.high" renderer, since the default scanline max renderer will not do gi. from here you do all the other basic settings for baked textures, except under output select "add", and then select "lightingmap", which i assume is a light map, however like i said i've never had to renderout light maps myself.
but the above should do the trick.