[ QUOTE ] use a 1024 x 1536 map (unusual size, yes, but still a power of 2) [/ QUOTE ] no, 1024x2048 would be power of 2. Always "double", you cant just sum with another power of 2 number.
I should clarify, multiple sets of UVs; but each covers a different part of the model. Eg the Head uses UV channel 2; and a 512x512 map; the Torso and Arms use UV Channel 1 and a 1024x1024 map; the legs use UV channel 3 and a 512x512 map; I don't see this being done as much with characters as much as environment pieces.…
engine dependent (like nearly everything). most will only allow one UV set, or sometimes 2 (diffuse + lightmap). I'd say modern engines give you more control. however I think most texturing is done with one channel, the others are more for effect stuff, like lightmaps (ambient occlusion...). You may mix detail textures on…
Why would you need different UV channels for those pieces? You only need different UV channels when the same geometry needs different uv-mapping (like Crazybutcher suggested with lightmaps for example) - unless you mean different materials for each part. All the different maps could all be on the same UV channel though.…