Preparing a model low poly for UV mapping

preparing a model Low poly for UV mapping.
by roja


Uv mapping is a skill that takes a lot of time, practice, and experimentation todo máster. Once you get it, and understand it, it really not very hard at all. It can be frustrating and take up bien todo much time if you dont do it properly or are lazy about it however.
What im going todo explain here is how i go about preparing, or setting up a model for UV mapping. I Will focus on a simple Low polygon, symmetrical, game model. There are, however, Many diferent ways todo go about doing this, mainly dependent on what your model is.
the importance of planning
Before you Even start todo model, you should a los be planning & Thinking about UV mapping & texturing. The reason for this is todo save you time with UV mapping when you get todo that stage. The best bien todo explain this is todo give some examples.

https://www.foro3d.com/attachment.ph...1&d=1244066409
Example 1 shows an image of a Low polygon house, with and without a wireframe.

Both UV mapping and texturing on this model was done Even before the modeling was Compleete. Let me explain. Take a look at the red colored woden beams in the fig1, they are repeated all over the model and the Windows are repeated to, as well as the Sharp pointed polls sticking th rouge the rof. If i had todo modeled this entire house, normal method would have ben todo first model it then UV Unwrap each repeatable part individually. Instead, y modeled 1 woden beam, then i UV mapped that beam, textured it(Although you can texture it at a later stage), then added it todo the model, duplicating the objects as i neded. Same thing for the Windows and other repeating Items in the model. This Will clearly save you a ton of time.

https://www.foro3d.com/attachment.ph...1&d=1244066409
A second example is for smaller repetitive objects in your model. In this example the monster has a spiked club, and a los a helmet with spikes on it. Se the highlighted spikes in the image. Similarly there are a lot of spikes in the model, and it Will take some time for you todo duplicate all those objects, rotate them, and place them. Again the most optimal bien todo do this is todo first model 1 Spike. Then UV map it, then duplicate and place it todo finish your model. So again, youre UV mapping before, you have the model finished.

https://www.foro3d.com/attachment.ph...1&d=1244066409
Example 3 shows a totally symmetrical model, that i modeled using an instanced* copy. Since i only actually modeled half of it, and i plan on making the texture totally symmetrical, y should only UV map half of it. So before joining both halves of the Mesh todo finish the model, it best todo UV map it at this stage.
*Even though this is not a modeling tutorial, y thought itd be important todo note this: an instanced copy is a sepárate object that is changed in the exact same bien as the original object is when you edit it. You can make an instance of your model by deleting half of it in edit model(básically splitting it in half symmetrically), then select the Mesh in object mode, and press Alt+d todo instance it. This creates a duplicate that is an instance. Then in object mode, in the Header bar click on object->mirror and choose an axis todo mirror the Mesh, and line it up next todo the other. In current Blender releases you can use the mirror modifier with similar results.

https://www.foro3d.com/attachments/1...g-example4.png
A fourth example is dealing with partially(or fully) asymmetrical organic forms, such as a character model that has parts, or all, of the texture, or Mesh asymmetric. The image shown below gives an example of a symmetrical Mesh(on the left), and an asymmetric Mesh(on the right). As you can se, the asymmetric Mesh has 2 diferent shoulder pads, 1 normal hand, 1 with a hok, and 1 normal leg with a bot, 1 with a woden peg leg. For this type of model, it is best todo make the complete model first.

Starting out
For the remainder of this tutorial im going todo use a completely symmetrical model as an example. Uv mapping on an asymmetrical model uses the same techniques, it just may take a Little extra time. Here is a picture of my finished model, ready todo be worked on for UV mapping:
https://www.foro3d.com/attachment.ph...1&d=1244066409
His body is completely symmetrical, as is his weapon. Right now there are 3 sepárate objects, 2 are the halves of his body, the other is the weapon. It easier todo kep the weapon as a sepárate object right now, and join it(select both meshes then Control + todo join) when youre done if you ned it todo be joined in the final Mesh. Were going todo focus on the body right now, so let deleete the one half and put the weapon on another layer, or hide it for now. So this is what weve got:
https://www.foro3d.com/attachment.ph...1&d=1244066409
seams
For an organic model such as this, y almost always use only 2 diferent UV Unwrapping techniques found in the UV calculations panel: LSCM Unwrap, and from window (planar mapping). The LSCM Unwrap function is nice because it does a sort of automatic Unwrap After youve defined seams on your model. I use the LSCM in conjunction with a planar mapping function because some parts of the model work best with one technique, other parts with another. Seams are necessary for LSCM todo work properly, but they a los have one other really nice característica, and that is that they let you select pieces of your Mesh in UV face select mode by pressing l and having your mouse cursor over or near the face. This Will become invaluable when we get todo the UV editing stage.

Ok, let start defining the seam. Were going todo start with a really easy part, the bottom of the fot. Start in object mode, press tab todo go into Edit Mode, then make sure youre in Edge select mode, because were going todo select Edges todo make the seam. Select all the Edges around the bottom base of the fot. Hold [shift key] as you select them so you can add Edges todo your selection. Then press [Control + e] and a pop up box Will appear.

https://www.foro3d.com/attachment.ph...1&d=1244066409
Click marque seam. Now you can de-select the Edges, and a seam Edge line Will appear. And that all there is todo making seam. You can a los clear seams todo incase you messed up or want todo change them, do so by pressing [Control + e] and chosing the clear seams option.

Moving along were going todo marque more seams throughout the entire model. This next picture shows a seam marked down inside of the leg, and around the waist. Remember you should make your seams in places that are not directly visible in the scene, just in case you have a texture seam showing. You a los want todo put them in places that make it easy todo break up the texture without causing visible seams(like a belt around the waist).

https://www.foro3d.com/attachment.ph...1&d=1244066409
Nest is the arm i defined the seam around the shoulder Joint, down and inside of the arm, and at the bottom of the hand as shown in the fig. Note that i a los hid parts of the Mesh(select áreas you want hidden, then press [h key]) todo make it easier todo click on the Edges. To un-hide the Mesh, press [Alt+ h].

https://www.foro3d.com/attachment.ph...1&d=1244066630
And lastly, the head. I went around the base of the neck, where his beard attaches todo his face, and because i want todo make him bald on the top of his head with some Hair on the back, y put the seam on the bak of his head todo reflect that. I a los put a seam around the face itself. Now were done putting seams on his body.

https://www.foro3d.com/attachment.ph...1&d=1244066630
Here an image of the seams i made for his Hammer weapon. I put seams around the circles at the ends of the cilindros, and a los a seam going along one side of the Poll.

https://www.foro3d.com/attachment.ph...1&d=1244066630
And that about it for the seam. Now let move onto the actual UV projecting and Unwrapping.
uv Unwrapping a 3d model using LSCM Unwrap and from window planar projection.

Interface setup:
Before we begin, id like todo mention that having a god workspace (or screen) set up in Blender with all the tools in your reach makes it a lot easier todo work with. I made a custom screen setup in Blender just for UV mapping. I have a 3d veiwport, the action time line showing beneath that(in case i want todo se the model in a diferent animation postura while texturing), the UV/Image Editor window, and a los the buttons window scrolled over todo the UV calculation menú(note that you have todo be in the UV face select mode, and the editing panel todo se it). Here what my UV mapping interfaz looks like:
https://www.foro3d.com/attachment.ph...1&d=1244066815
After you have a god setup like this or todo your liking, we can begin.
using LSCM projection mapping:
Select your model, and go into UV face select mode by pressing [f key], or by chosing that mode from the menú the 3d veiwport panel. Your model Will turn white. Make sure you have draw seams, draw Edges, and draw Faces all selected in the UV calculations menú, like this:
https://www.foro3d.com/attachment.ph...1&d=1244066630
Next, we ned todo make a new image in the UV/Image Editor. Click image->new, then in the box that pops up type in a name if you want to, and a los your texture size then press ok.

https://www.foro3d.com/attachment.ph...1&d=1244066630
https://www.foro3d.com/attachment.ph...1&d=1244066630
Normal texture sizes for games are square and follow the Powers of 2 i, e 64, 128, 256, 512, 1024. So choose the one that works best for you. As a side note, y find it best todo work in a texture size that is bigger than what Will eventually go in the game. So if my texture size is 256 por 256 in the game, ill work with one that 512 por 512, and resize it when the time comes. This is because it easier todo work with a larger size (as long as it not todo large), and it preserves more detail if you ever want your texture todo be bigger.

A black box Will pop up in the UV editor, you may have todo zoom out a Little todo se the whole thing. Now, making sure youre still in UV face select mode with your model, press [a key] todo select all the Faces. They should all become highlighted, and youll a los se some boxes pop up in the UV editor-those are the Faces that we have todo Unwrap.

In the popped up UV calculations menú, click on LSCM Unwrap. The LSCM Unwrap function uses the seams we created todo Unwrap the Faces. You should get something similar todo this, depending on your model of course:
https://www.foro3d.com/attachment.ph...1&d=1244066630
Now, as you can se, weve got some clean up work todo do. Were going todo have todo do some work todo resize, rotate, and move the pieces around todo fill up the texture space and todo lay them out as we want them.
the UV test grid:
When UV mapping a model, you generally want todo kep all pieces in proportion todo each other as much as posible todo prevent texture stretching. So a god bien todo se if parts are being stretched is todo turn on the UV test grid. To do this, click on image->new, and making sure your texture size is correct, click on UV test grid and click ok. Now youll se something like this:
https://www.foro3d.com/attachment.ph...1&d=1244066630
We a los want todo se this texture on our model. If youre not already in texture mode in the 3d viewport, place your mouse over the 3d viewport and press Alt+z, or click on the viewport Shading button in the Header and click textured. Now your model should look like this:
https://www.foro3d.com/attachment.ph...1&d=1244066932
Ok, now we can start todo size the diferent UV pieces and se them updated on our model using the grid texture. The grid texture can be annoying todo view the UV properly at times, so you can always turn it of by making a new image texture and deselecting the UV test grid. As you look at your model youll notice that some of the grid blocks are larger than others, that where the UV are stretched, they dont accurately represent the proportions, so youll have todo make up for that by moving the UV vértices around as you work on Unwrapping. Ideally, you want the colored grid boxes todo be the same size across the entire model(or as close as posible).

Frequently used hotkeys:
Working in the UV image editor uses a lot of the same hotkeys as modeling does. Press a todo select all, a again todo deselect. G moves the vértices, s scales, r rotates, b for the selection draw rectangle, for mirror. Alos a very powerful hotkey is l, for selecting an element or group of vértices(just hover your mouse over them and press l). You can a los do this over your 3d model-and select an entire group made with seams as one example. Doing that makes it fast and easy todo isolate áreas you want todo work on, without bothering the rest of the Mesh or UVS.

In addition todo the hotkeys mentioned above todo place the UV into this position, y a los use a few other functions todo do diferent things. To place 2 vértices right on top of each other(like merging them), select them both, then press s then 0 (that is a zero). Or you can just scale (s) them until they are as close as posible, in the images below, you can se that i made the vértices of the front and bak Edges of the torso in a straight line. I did that by selecting all of them on the edge, then pressing s then x then 0. This aligns them all perfectly on the x axis. Substitue x for y if you want them lined up horizontally, sometimes it hard todo tell what face lines up with the connecting face from another group. To do this, go into active face select mode by pressing c in the UV editor, or clicking select->active face select, then click on one face from one group, and you Will se it becomes highlighted with 2 white Edges, one green edge, and one red edge. This highlighted face is a los shown on the 3d model. So by selecting diferent Faces you can se what lines up with what. This a los makes it easy todo select and move one, or a group of Faces at a time, instead of picking up vértices.

https://www.foro3d.com/attachment.ph...1&d=1244066932
There are a lot of diferent functions that you should try out and play around with located in the UV/Image Editor drop down menús.
unwrapping & placing:
I start of by working with the torso and leg UVS. I want todo combine them together so that they Will be seamless along the waist. As long as youre not wasting neded texture space, it a god idea todo combine 2 parts whenever posible.

https://www.foro3d.com/attachment.ph...1&d=1244066932
Moving on todo the face, im not happy with how the LSCM Unwrapper made it. I rather Paint it straight on, as it more natural that way. So what im going todo do is todo use planar mapping for the diferent pieces of the head, in addition todo the face, then attach as Many Edges todo each other as posible.

Each piece neds todo be isolated in the UV editor, and mapped one at a time. So first make sure all UV Faces are deselected in the 3d viewport and UV editor by pressing a in the 3d viewport. Then, selectively press l on the group you want todo start with, let do the face. Only the vértices of the face Will appear in the UV editor. Hover your mouse over the 3d viewport and press 1 on the num pad todo give you a front orthographic view(note that if you didnt position your model facing this direction it wont be a frontal view-you can change that by rotating your model so it Faces the front). Now go todo the UV calculations menú and click on from window:
https://www.foro3d.com/attachment.ph...1&d=1244066932
And below is another before/After picture showing the result of planar mapping the face, top of the head, side of the head, and beard, then joining some Edges together, and moving some vértices around(unwrapping) a Little.

https://www.foro3d.com/attachment.ph...1&d=1244066932
For each piece i used a diferent view from the 3d viewport then i UV mapped it from that view-not all were done from the frontal view. So for instance with the top of the head, y first selected only those Faces by pressing l in the 3d viewport, then on the num pad press 7 for a top down view, then i clicked on the from window button. Press 3 for a side view(side of the head).

After doing a few more adjustments, and laying everything out with the least amount of blank unused space posible, this was my result:
https://www.foro3d.com/attachment.ph...1&d=1244066932
And now were ready for texturing, the UV mapping is all done*. You can now duplicate the other half of your model and join the pieces together.
*as you texture the model, you may have todo do some small tweaks with the UV here and there, but try your best todo kep them todo a minimum unless there is something majorly wrong.

Using Blender texture painting mode todo create an outlined underbase.
*note that this tutorial requires you todo have a properly UV mapped model all ready todo be textured.

Blender texture painting features cannot replace a god 2d Paint programa, but it can be quite useful in blocking out important details that can be hard todo find the right placement of such as eyes, muscle lines, etc. This bien youll be going bak and Forth between your 2d programa and Blender a lot less, because you can get the placement right the first time.

So we start by having at least a 3d viewport with a model all ready todo be textured, and the UV/Image Editor open. Click on the button that looks like a Pencil:
https://www.foro3d.com/attachment.ph...1&d=1244066932
Then click on view->view Paint tool.

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The image Paint box Will pop up:
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Here you can choose the color of the Paint, the brush, size, opacity, etc. Play around with the diferent features and Paint strokes on the canvas todo se what does what.

A few tips todo note:
1. You cannot undo. If you press undo in another viewport, you Will undo all painting you have done. If you press undo in the UV editor, nothing happens.
2. Right clicking in the UV editor in Paint model Will select the color beneath the mouse-a very handy característica.
3. It a god idea todo turn of draw Faces under the view menú of the UV/Image Editor. This is because the Faces are slightly shaded, and if you right click on them todo pik up the color that darker color Will be picked up instead of the real Paint color underneath.
4. Make sure you have update automátically turned on in the view menú.

And here what a really quik block in can look like:
https://www.foro3d.com/attachment.ph...1&d=1244067121
https://www.foro3d.com/attachment.ph...1&d=1244067121
You can certainly spend more time and detail on it in Blender. Since i plan on taquíng it todo a 2d Paint programa, y didnt bother with making it look pretty, or getting the colors correct. Just enough todo get the details i wanted placed. You can then click on image->save, todo save your Painted texture.

And here is what my model and texture look like completely finished:
*note that i did use a 2d Paint programa todo do the full texture, not Blender.

https://www.foro3d.com/attachment.ph...1&d=1244067121 https://www.foro3d.com/attachment.ph...1&d=1255194121
As a final note, y encourage all new comers todo experiment with the diferent tools Blender ofers for Unwrapping, as that the best bien todo learn-to se what they do (in addition todo reading the manual. Dont be afraid todo push buttons, just make sure you saved your file first.

By roja. www.blenderart.org.