UV unwrapping has nothing to do with rendering, so any Cycles errors you're getting are a total non sequitur.

Select your object, go to Edit mode, select all, press U on the keyboard and select an unwrap method. That's how you do UV unwrapping.

You have to have all four textures for the Workshop to take it in. If you don't have jug_normal, jug_mask1, and jug_mask2, the importer will reject it.

Sort of a follow up to my older 'Making DOTA2 Shader Masks in GIMP' tutorial, I thought it would be neat if you could actually paint the shader masks directly on the object using Blender's paint tools, and also see the effects that they have in real time.

Turns out that's totally a thing that can be done, and I spent the past few days tinkering with GLSL viewport rendering and the Blender Internal nodes system to create something that works (I think) pretty well.

I also cover using Blender's Compositor and GIMP to generate the actual mask image files in a manner that's a bit quicker than the method in my older tutorial.

You can watch the tutorial here.

Be forewarned: It's about an hour long.

More of a quick tip than a tutorial, but since I hadn't been able to find any good resources for this (everybody seems to say 'just use Photoshop' when asked), and I finally figured out something that actually works pretty well I figured I'd do a quick haphazard video tutorial:

Feel free to check it out

I'm using GIMP 2.6 because the GTK library used in 2.8 has some issues with pressure sensitivity not working, but the fundamentals will work in whatever version of GIMP you're using.

I figured it out. The masks don't seem to read properly if they're sized below 2048x2048, which resulted in blacking out the texture. Scaling it up fixed it.

I actually don't think it's a GIMP problem.

http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=218789968

See how in the screenshot in the main view the texture on the helmet is fine, but in the portrait and detail views it's black? If it were an issue with GIMP it would be black in all views.

I can't figure this out. I've got white in the corner of my alpha channel for mask1, and the rest is full black, and the item will be full black after import. If I set the alpha channel to 0,0,10 (HSV), my colour texture will show up, but since now it's self-illuminating it doesn't shade properly.

Does anyone else have this problem? Is this an issue with GIMP's TGA export? Or is the DOTA2 importer doing something wrong?

[edit]The item shows as full black when viewed in the importer, but when doing the in-game test the color texture shows up fine, except in the portrait and the detail view.

I've found it useful to move the rig and the player model so that the primary bone that the item is being parented to is at 0,0,0, then aligning the item, parenting it to the bone and exporting from there.

Overlapping the UVs is a bad idea because it can cause issues with your baking. If your UVs are symmetrical you start out with your layout overlapped, and then move the islands for one side exactly 8 units to the left or right (it should look like two identical layouts sitting right next to each other, one on the grid and one off) and they'll get the same texture, and you won't have to worry about an overlapped bake.

Thanks for the kind words! They were both kind of proofs of concept and getting used to the ins and outs of Blender and the TF2 importer after several years of not spending any serious time doing 3D modelling (and it being with Lightwave at the time).

I've got a couple other ideas for things to make, one for DOTA2 that is going to be really hard, and another TF2 one that shouldn't be TOO difficult.