How to rescale UV to replace with a higher res texture?

[SpaceNavy 16]

So like the title says, we want to improve a texture that was UV'd too small on the original model.

Is there a way to rescale it and move it to its own separate texture without have to restart the whole O2 process involving selections and weights?

[warlord554 2065]

rescaling up will almost always artifact at some point, rescaling down ofcourse yields better results. You can try to resample in something like gimp or photoshop, but I highly doubt your going to get HD results

[SpaceNavy 16]

rescaling up will almost always artifact at some point, rescaling down ofcourse yields better results. You can try to resample in something like gimp or photoshop, but I highly doubt your going to get HD results

What do you believe would be the best course of action regarding this then? Forgive me, I'm not very good with O2 so perhaps there is a feature with texture mapping that I am missing.

We have a selection for the uniform already in O2, so would it be possible to unwrap the model into a completely new UV and only have to redo the texture itself? It isn't the whole model that needs resized, only a certain part.

[warlord554 2065]

I don't use O2 unwrap, so I couldn't tell you. I always export into another 3d program and do my work (UV mapping, etc), then import back in

[da12thMonkey 1943]

I'm almost 100% sure that changes to the UVs inside O2 wont effect any selection names and vertex weights on the model. It's only if you export the model back to a third party app and re-import to O2 that you might risk losing that info.

Open the UV Editor in O2 (the little button in the toolbar that says 'UV'), select the UVs you want to rescale. It helps if you use \Filter\Filter by main texture to isolate the faces that belong to the texture you want to modify the UV space for, or move to another texture.

If you want to you can try and edit the UV maps here by rescaling and translating UVs to better match the use of texel space that you want, without moving it to a new texture. Then if you export the new UV output and try to match any re-arranged UVs by translating and rescaling parts of your texture in Photoshop until everything is in it's new place. The major difficulty here is simply re-arranging the UV space efficiently in a way where everything fits in and looks as nice as it needs to be.

It's probably better if you use the numeric UV transform tools in the UV window (the yellow rotating square button - 3rd button to the right after the one that looks like a Magnet) rather than the analogue mouse controls. Mainly because then you can take notes of the amount by which you transform the UV shells and enter the same values when it comes to moving the same model parts in the lower LODs and getting everything to match up.

However, if you do want to give the whole object it's own texture map. After selecting the parts you want to upscale, click \Edit\AutoSelelect in Object\. Return to the main O2 window with the viewports and you'll see that the faces you selected in the UV editor are now selected in the model itself. Press the [E] key to bring up the face properties window and in the "Texture" field choose a path to a blank image of the dimensions you want the new high-res texture to have (e.g 512*512, 1024*1024 etc. etc.) Those faces will now be separated from the old texture path and have a path of their own. You can now go back to the UV editor (change the filter so it sorts to your new texture instead of the old one) and rescale them to fill your new UV space. Then you just need to remake the texture at higher resolution on that separate image to match the new UV layout.

Assigning another texture to the model in this manner will increase your "section" count by one. Sections are your texture+material pairs, so the more texture and .rvmats your model has the more sections your model will have and the more resource hungry it will be ingame when the engine calls on your hardware to draw the scene. The section count is shown in the bottom left of the main O2 window.

As such, you probably wont want to make you new texture super-high-res: Just big enough that you can output a new texture that has an acceptable texel ratio on the upscaled UVs.

You'll need to repeat this process for any other LODs that you want to use the high-res texture, but it's probably worthwhile to allow the lower LODs to use the old texture and UVs and save adding an extra "section" to all LODs of the model: It's unlikely that you'll notice the low-res textures at the distance that the lower LODs pop up (and the game will mip-map them anyway), so it's a bit of a waste of time moving the lower LODs to the high-res UV layout.

Like warlord said, you'll want to re-draw any upscaled parts from scratch regardless of whether you give them a new texture or just rescale the UVs on the existing UV space, because simply upscaling the parts of the image will probably make your textures look no better, since the texels-per-cm count on the model is still basically the same as when you had the low-res texture.

You'll also need to make new .rvmat Material textures (NOHQ, SMDI, AS etc.) at the increased resolution and apply them to the faces you extracted and assigned with a new Texture, via a separate .rvmat file. If you've baked the materials you'll want to export a copy of your model with the new UV layout and re-bake the textures for that part of the model again using whatever software you use to do that. But simply assigning these new material bakes from the new output images via the .rvmat will be enough to get them on the model in O2 - You wont need to re-import the model you exported after baking, and risk losing your selection/weight info.

Edited January 9, 2015 by da12thMonkey