Is it possible to generate one PNG file which consists of many PNG files that can be used to create a texture2D object. What I mean is, I downloaded a 3D model with which instead of one PNG texture file they had multiple PNG files (e.g 1 for engine, 1 for wheels, etc.). I don't know how can I combine it into one PNG texture2D file that I can import in UDK.
What if the order goes wrong, and the engine part of the texture shows on the wheels?
Yes that is possible but probably more work than you want it to be.
in this case you just need to make multiple materials for the static mesh, when you open the static mesh to apply the textures there's a LOD pull down that contains all the slots for materials on the model.
You want more materials on your model only if they will be different. For example one part is wood and other is metal. Or somethng like that. But you should try to avoid putting lots of materials (more than 3) on one model if its not for pre-rendered scene (cinematics).
Oh I see...Oy my supidity again...U want a model with two materials?...In the static or skeletal mesh editor, when U click on the material slot, the faces it applies to should light up...If U want to use one texture, then your uv map for all parts of the meshshould not overlap...then U can texture one part wood and the other metal...am I close to being right?
There isn't an automatic way to create texture atlases from multiple image files. You'll need to modify both the textures and mesh in order to do this properly.
1) You need to use an image editing software to combine the multiple image files into a single texture. Adobe Photoshop (Premium) or GIMP 2 (Freeware) are usually good options.
2) You need to use a 3D model editing software to modify the UV maps so that they reference the correct section of the texture atlas. 3DSMax/Maya (Premium) or Blender (Freeware) are usually good options.