Just wanted to quickly summarize the workflow using Maya and Vray to bake textures so that they can be used in game engines.
1) Create your models inside maya, try to combine meshes of as many objects as possible and make sure you have defined good UV sets for all those meshes .
2) Then go to Vray common render settings inside Maya and change Baking engine to Texture baking.
3) Then select your mesh for which you want to bake your textures for , Go to Rendering menu -> Lighting/Shading -> Click:Assign single Vray bake option to selection.
4) You will have vraybakeoptions node attached to the mesh you had selected. Now in this node set the output path for your texture, this is where your texture will be saved to.
5) Next under Lighting/shading menu , click on :Bake with Vray option box . In this box you can click on Assign baked textures , if you want to preview how it looks inside the viewport.
6) In the same menu, click on “Bake”. At this point nothing might happen, everything will remain same and you might wonder if its not working.
7) So, if you remember we had changed the Baking engine to texture baking. This means that we first have to press the render button in the render view and this is when the actual texture map gets calculated. So, when you hot the render button this time you wont see the camera render , you will see the actual texture map.
8) And now if you go back to the lighting/shading -> Bake with Vray option -> Bake , Vray will take the rendered texture and Bake it to the mesh and it will be placed in the output folder path you had mentioned .
9) Then you can just export the mesh as a .fbx file and import that into a game engine and also import your Baked texture , just assign
your baked texture and you are good to go.
Here is a screen shot of a scene in Maya with the textures baked on to the mesh