UV Mapping (Yes, again)

[giorox 1]

So many of you might have seen a very similar topic to this, and yes i did search the forums, and not just this one, also searched on Armaholic/Ofpec and googled and came up with a few UV editor tutorials. Though none of them actually made me understand UV Mapping better, i read and re-read, and i am kinda getting frustrated at UV mapping, since this is, to me, the last big step until the config files for my first addon.

Now i am here, in your presence, asking for some help on UV mapping, as my understanding of this topic is so low, it could be considered invalid.

If it helps you, this is my model (in .p3d format):

http://www.mediafire.com/?xg1b7utsw7ufnik

And a screenshot if you would prefer:

[max power 21]

Perhaps if you asked some specific questions.

Generally, UV unwrapping, or UV projection (both the same thing), is a way to project a 2d image onto a 3d object. The easiest way to think of it is like an orange peel. Say you want to paint onto the peel of an orange, but you can only (for some reason) paint things that are flat. You have to figure out some way of peeling the orange. So, you take the surface of the orange and peel it by making cuts in it and peeling it off until it lies flat. Now, unless you cut it into little bits, there are always parts that are not going to lie completely flat. This is like UV distortion. If you make too many cuts, you're going to have seams all over the place and it's going to be fairly hard to paint. The trick is finding the best way to unwrap some 3d object onto a 2d grid and finding a balance between distortion and number and location of seams.

Edited December 3, 2012 by Max Power

[PuFu 4600]

seen this thread from work and i was gonna reply to what a UVW Unwrapping is, and what UV mapping is, but Max put it right on the dimme for you.

I am gonna add just this: a 3d model is in fact composed from a number of faces and vertices in space. A texture is a 2d image. Uv mapping is brigging the gap between 2d and 3d, telling the engine (be it render engine or game engine = real time render engine, in this case RV), how to take to "squash" and "slice" the 3d model onto a flat plane, without overlapped faces

here is a very simple example:

a cube

You can unwrap it in numerous ways. Here is just 3 ways i put down quickly.

click for larger

You would say hey, but a cube has all the faces exactly the same. Yes, that is true, and this is precisely where it gets interesting

a sphere (not the one where the top is composed of triangles, but a proper only quad (4 edged face) ready for subdivision:

click for larger

From right to left:

1. face by face flatten unwrap (there should be no issue to distortion, but the seams are very visible - too many uv islands)

2. 30 degree angle flatten unwrap (some distortion, less uv islands, some seams will be visible, need to manually align islands on axes)

3. unfold (no distortion, one single uv island, but less likely to arrange according to UV axes (similar to 2D XY axes).

4. loop unfold (one single clean UV, cannot apply to all objects).

case of point, an uv can be done multiple ways. The thing i learn from experience: try to split the UV into islands by smoothing groups, and materials that you'll be using. Do not fear of more uv islands, but try to keep as little distortion as possible.

regarding UVW unwrap in O2: i find the tools (or in fact the lack of proper UV tools) so frustrating that i have never ever used it for anything more complex than very simple shapes. So you'll have to wait on someone who uses O2 for UV-ing.

Edited December 3, 2012 by PuFu

[Messiah 2]

It is however quite possible to achieve a uv unwrap with O2, but its rather frustrating and tedious, so if you have the oppurtunity to learn how to unwrap using a better tool, then do so, however if you're stuck with O2 (or stubborn like me) then this is a brief tute I wrote on the subject:

http://forums.bistudio.com/showthread.php?69734-Oxygen%27s-UVEditor&p=1220584&viewfull=1#post1220584

and the pictures to accompany it:

https://lh4.googleusercontent.com/-gvAExag4TT4/T9J5ebwMPqI/AAAAAAAADmw/99wGzIJUO6M/s0/unwraptute.jpg

like the orange example, you're essentially just trying to unfold your object so its flat. Like the cardboard boxes you use when moving house, they're nothing more than a series of flat sides that when constructed become a 3d object. Of course, some measure of thought needs to go into how you unfold things, to prevent bad seams where faces meet, or distortion.

don't run before you can walk though, experiment with unwrapping a box, then a cylinder, then how to split up more complex objects. In time it becomes fairly obvious how a model needs to be unwrapped so to ensure a better UV and seams.

[giorox 1]

Thank you sirs. I had a basic idea of what UV mapping was about. So that helped me. Sorry for not asking any specific questions, it's just the fact i had nothing to base myself off.

[meshcarver 12]

A quickie about organic shapes; as they are notoriously difficult to do seamlessly, i'd advise unwrapping the uvs first and then if you can open the 3d model in photoshop it has a simple to use 3d paint tool.

There are numerous youtube tutorials about this.