Texture Unwrapping (Skinning) Tutorial

[ProtoArmor]

Hello, I felt that everyone should get a copy of this tutorial.  It is an e-mail sent in response to Werner when he asked how I did the texture for the Ion Condenser model:


Well, I pretty much do all texturing by hand (notice that I do my original modeling in the open-source Wings3d, which is the easiest AND most powerful tool for low-poly and box-method modeling that I've used--I then import the model into Blender for texture mapping).  Most of my GIMP files have about 12 layers or more, which gives it depth: I have seperate layers for the base texture (coloration etc), the fine noise, the course noise (just noise stretched out by about 20x size), the lines, the vents, the dark areas, the light areas, the seams,  and so on.  Then I can adjust the transparency of each layer.  I also make the TOP layer the unwrapped wireframe, created by the Blender unwrap feature that shows where the model's wires are (I then use the GIMP Color->Alpha feature to make all but the wires transparent),  and turn the layer on/off at will.  To make the low-poly circular vent on top look like a smooth circle, I just use the circle tool in GIMP and then shade it using a big soft brush where I imagine dark or light areas would be, then invert the selection shade around it where I imagine dark or light areas would be (remember, all this is in a new layer so I can adjust it later).  While working, I constantly use the "Save a Copy" feature (after making the wire layer invisible) in GIMP to a JPG which blender applies to the object (Blender view window is in Textured mode).  I then use the Blender "Reopen Last" feature to reload the scene so the JPG texture is updated).

• IMAGE EDITING: There are many PhotoShop tutorials online so you can learn more about how to make things look 3D.  It helps to have those examples, and some imagination (and brushes of varying sizes and sharpness, and creative use of the selection tool and "Select From Path" feature of GIMP) to decide how your low-poly object would be lit if it were high-poly.
• UNWRAPPING:
• Blender3D: Noob to Pro/UV Map Basics
  
  • Using this tutorial, the map won't work in the final render, but will show up in the real-time render, which is what really matters for this type of texture work.
• If the texture doesn't unwrap nicely, change or add seams.  For example, I had to make the seam for this one down the side of the protruding pipe.  This allowed the unwrapping function to very nicely cylindrically unwrap the pipe.  After it is unwrapped, you can use the UV window to move the points around wherever you want.
• ALWAYS: Select all UVs in the main window, then select all UV points in the UV editing window, then stretch the points to cover the WHOLE image (to make best use of resolution (hit 'x' or 'y' on the keyboard while scaling to scale along a particular dimension).
• To move separate seamed areas to arrange them to make more efficient use of resolution (the less blank space in the UV Window, the more pixels are used), select one point then use the "Select", "Linked UVs" to select all of the points in that seamed area (i.e. if the pipe mentioned above had an additional seam all the way around it's base, "cutting" off a new uv map section).  Then you can move each seamed area (there will be only one seamed area if you didn't create any seams that completely cut off an area).

-ProtoArmor

> Hi ProtoArmor,
>
> thanks for the model of the ion condensor :D i've committed it recently into SVN. We'll jopefully integrate it into the gameplay soon.
>
> One question concerning your models: Do you make them in Blender? And how much of the texture work do you do in an image-manipulation program afterwards/parallel?
> The reason i ask is simple. I've made alot of crappy models in my past and no matter what technique i use and how much time i can't get a nice 'baked' shading on the model... similar to the ones you used on the condenser. Using baked radiosity is one possibility i know of (and global occulsion), but i never reach the possible quality others do.
> Do you have tips or hints on that matter (even better if it's in blender)?
>
> Thanks,
> Werner

[Mattn]

i´ve posted it in our tutorials section, too:

http://ufoai.sourceforge.net/tutorials.html

thanks

[Hoehrer]

thanks for the long answer
I figured out that we use very similar steps when making models/textures, but the main difference is that you do alot of the texture work by hand ... which i'm not really good in :-/

To compensate a bit for my lack of artistic skill in the texture area i try to e.g. use some of the blender-scripts out there and other tricks to get a good ground-layer in gimp.

What i normally do:

• Assign _basic_ materials to the model ... using vertext groups for different materials in one mesh. I mostly use materials from the blender-material collections out there (the blender material CD has been open-sourced recently but also create custom materials (they are then included in the .blender-source file)
• Enable "ambient occultion" in the world-setting and set it to values that will blender calculate some of the shading for me. It's slow (ray-tracing) and not perfect, but i kinda like the results.

Note: The downside of this is that you lose bumpmapping and you cannot use additional lights (these two issues are of partly related).. otherwise the renderd output will be messed up. I have palyed with this and found some solutions, but they are time-consuming :(

• Then i use the BRayBaker script to bake the materials to the uv-map (slow: see above) and save it as an image to be used later as the ground-layer.
• Then i export the UV-grid .. for the same reasons you do it
• That's it mostly. There are no details yet, but the shading is there.

Details how i do them currently:
I really like to model seperate parts of the model in detail and then use them as a texture.
Let's take the vents again ... I'm modelling them in relatively high resolution, and render them with ambient occulsion and myabe some lights to a smaller resolution than the ground-layer ... then i export them to an image file and use them as new layers in the gimp.
Of course i still have to blend them in without seams, but i that's easier for me than to draw them by hand. :)

You can see an example of this in the
models/aliens/hovernet/hovernet.blend
and
models/aliens/hovernet/hovernet_engine_top.blend
files ... it's a WIP and far from finished, but if you go through the layers of the engine-file you'll see the different details of the hovernet-texture.
You might notice that the hovernet.blend doesn't have the texture-file assigned as material, but the original procedural materials ... so others can play with this as well.

Thanks,
Werner