I'm making a building with a corner shaped like a triangle and I'm having trouble applying textures to the selected vertices. I want to apply textures to every side of the building. I change the shape of my building with the vertice option under Edit Mesh but still that triangle and the adjacent side share the same textures and I want to apply textures to that triangle seperately. My building was constructed using the box option. Here an example of the building from the top view:

When you apply the textures, which method are you using? For my Tacoma Narrows Bridge scenery, I created an object similar to yours for the pedestals to the Tacoma Narrows Bridge towers (this package is still in the works, yet to be released).What you need to do, after converting your box to an editable mesh, is to go into the modifieer tab and select "UVW Mapping." After you've selected UVW Mapping, you'll see a list of options giving you choices on how to apply the textures, such as Spherical, Cylindrical, Planar, etc. Select the one that says "Box" and then expand that modifier. Afterwards, click "Gizmo" and then go to the dimensions. At first, it'll give you the dimensions of your box. For instance, if your box is 18 meters long, 10 meters wide and 25 meters high, change your UVW Mapping "Gizmo" modifier to a 30x30x30 box.Now, right under the modifier that says "UVW mapping (in the modifier selection pane) select "Unwrap UVWs." This gives you the correct shape of your UVWs to work with (if all worked well). It takes some experementation, and working in the "Perspective" viewport to get things to look right. My bridge tower leg cells for the Tacoma Narrows Bridge were simple boxes in the shape of the Red Cross (viewed from overhead) but it took over an hour and twenty minutes to get them to look right!If things don't work after trying these suggestions out, let me know. Also, it helps to read the gmax scenery design tutorial that came with the gmax gamepacks SDK download.

You can add different textures to different Polygons, not to vertices.Vertices are the blue points at the corners of your polygons.If you choose a polygon and drag the texture on to it it should work.

The problem is that when I want to apply textured windows to that triangle, the windows lean to one side and share the texture with the adjacent polygon in which the windows appear normaly aligned.

You will have to map your texture for that specific polygon after you have applied it. That way you should be able to get the windows display like you want.In this case the Unwrap mapping is probably easiest, although I use the UVW mapping in most cases.