Quote:
Originally Posted by Kendras
I have a question.
I exported the 3D model of the Yamato's hull from S3D : I exported 2 things : NBB_Yamato.obj and NBB_Yamato-uv2.obj.
Then, I remodelled the NBB_Yamato.obj in Wings.
Now, I can only import the NBB_Yamato.obj, and not the NBB_Yamato-uv2.obj, is it a problem ?
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The short answer is:
Yes, it is, if your model used an ambient occlusion map. If it is not, and you don't plan to add one, just scrap the *-uv2.obj file exported by S3D
The long answer is:
The UV projection of the main obj file is used by the game for mapping on any 3D mesh its diffuse texture (i.e. its "skin"). Uv2 object's UV projection, on turn, is usually employed for ambient occlusion textures (i.e. a texture containing prerendered shadows), but the latter can include dirt maps (i.e. rust, scratches, etc.), camouflage schemes and, if their resolution is high enough, markings, emblems, hull numbers, etc. The two objects must have identical vertex/edge/face coordinates (that's why S3D refuses to import the the *-uv2.obj after you modified the primary obj file), but indeed they can have different UV coordinates.
The reason for having two sets of UV coordinates is that diffuse and AO textures have different prerequisites.
One of the main requirements of a diffuse texture, is it looking sharp. A trick used in videogaming for having fairly sharp object skins without increasing too much their texture resolution, is creating objects with "overlapped" UV maps, i.e. objects set in a way that the same portion of texture is mapped on more than one region of the 3D mesh. If the iterated texture is omogeneus enough, and if its edges are "seamless" (i.e. tileable), or if it is mapped on non-contiguous regions, the trick wont be apparent and the player will be happy
On the contrary, being based on 3D objects' topology, AO shadows are not esily fitted on an overlapped UV space. The same goes for various markings and other eye-candies, which are not supposed to be repeated n times on the same objects, or for camo schemes whose lines and patterns usually need to be matched carefully. This is where having a secondary UV projection comes in handy, for making the player even happier
Hope it helps
