Quote:
Originally Posted by Targor Avelany
I'll go through all of it today and see what happens, looking for difference between the files.
Also, AO obj: I still have no use for it and don't understand why is it getting sepparated. So far, you can pass the AO map through the textures/material maps, so I'm not sure why is there 2 objects and mtl's.
That is why I generally just import both of the same.
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I can answer this question:
often diffuse textures are tiled along a model. This is especially true for big models like ships, which otherwise would require huge textures. As long as textures used are homogeneous enough, and UV maps are placed wisely, you won't notice the repetitions, and the same pixels can be used on various parts of the model. This involves overlapping UV maps.
AO maps are another matter though: being caculated on the base of models' topology, there is a little chance that their texels can be used effectively on more than one area of their 3d model. Even if the model had many similar elements (which would correctly use the same portion of a diffuse texture) they would probably receive different internal shadows, depending on other surrounding elements, and they would therefore require each its own portion of the texture. On the other hand, shadows baked in AO maps don't need to be as detailed as the particulars usually painted on diffuse maps: for their nature shadows tend to be blurry anyway. As a consequence, a good AO map should contain little or no overlapping, with many small elements crammed over a relatively small texture area.
The obj format don't support multiple UV sets. The workaround used by GR2 Editor and by s3d, is importing the two UV sets from two copies of the same model, with identical vertex coordinates but with different UV maps. Nonetheless, if you are not going to use an AO map, or if your AO map uses the same coordinates as the diffuse one, you can discard the second UV set (thus reducing file size), and eventually overlap the AO on the diffuse texture as I did with the barrage balloon.
