After unwrap, you need to arrange the UV maps into something that can be logically painted. Your goals for editing are:
- Arrange the different UV maps together into a coherent layout
- Stitch some pieces (UV maps) back together
- Minimize wasted space in the image
- Enlarge the 'faces' where you want more detail
- Re-size/enlarge the 'faces' that are stretched
- Shrink the 'faces' that are too grainy and have too much detail
With a minimum of dead space, the most pixels can be dedicated to giving the maximum detail and fineness to the UV Texture. A UV face can be as small as a pixel (the little dots that make up an image) or as large as an entire image. You probably want to make some major adjustments first, and then tweak the layout.
When you have unwrapped, possibly using seams, your UV layout may be quite disorganized and chaotic. You need to proceed in two steps: Orientation of the UV mapping, and then arranging the UV maps.
3D View: Face Mirror and Rotate UVs
Recall how the red and green outlines show the orientation of the UV Texture relative to the face? Well, you might find that, for example, the image is upside down or laying on its side. If so, use Face->Rotate UVs (in the 3D window in Face Select mode) menu to rotate the UV layout in 90-degree turns. The Face->Mirror UVs to flips the image over like a pankcake in a pan, mirroring the layout and showing you the image 'reversed'.
Merging UV Maps
Each time you unwrap, Blender creates a set of UV Coordinates shown in the UV/Image Editor window. So, if you unwrap 2 sides of a cube, and then 3 sides, and then the other remaining side of the cube, there will be 3 sets of UV Coordinates or UV Maps. You would unwrap this way if you wanted to use three different images for each of those maps. However, if you change your mind, simply select all the faces (for example, all 6), and re-use the Archimapper, the UV/Image Editor window's UVs->Unwrap menu item. The maps will be recomputed to be non-overlapping.
Separating UV Maps
If you want to use a different image for a particular set of faces, but those faces are already mapped to a different UV Texture (image), simply select only those faces and unwrap them again. In the UV/Image Editor window a new map for them will be shown, and you can assign a new image to that map.
Arranging the UV LayoutLock button pressed you will also see real-time feedback in 3D of what you are doing. Scaling and Translating of vertices can be done in the local X or Y axis of the map if needed. Just press X or Y after entering the scale command (S). Proportional editing is also available and it works the same way as in Edit Mode for meshes. Vertices in the UV Editor can be hidden or shown using the H and AltH respectively, the same way as in Edit Mode.
RMB select one of the UV coordinates, and use Select->Linked UVs (CtrlL) to select connected UVs, not border select because UVs from both will be selected.
Deleting a UV Layout
A mesh can have multiple unwraps, each resulting in a UV map for that section of the mesh that was selected. You may get into a situation where you just want to delete everyting and start over. In the Buttons window, the Editing (F9) buttons, there is a Mesh panel. On that panel, click the fat X (Delete) button next to the name of the UV Texture you want to delete. If you delete every entry there, all the UV layouts for that mesh will be deleted and you will be kicked out of UV Face Select mode. The second that you re-enter UV Face Select mode, you create at least one base UV Texture.
UV/Image Editor Menu
When working with a UV Layout, 99% of your time will be spent in using the UV/Image Editor window. There are many options and features in this window to make you productive. The header consists of a menu, an image selector and a few buttons. Some of the menu items and buttons are relevant when using UV textures. Only the ones relevant to changing the UV layout are discussed in this section.
This menu controls how and what you see when working with UVs:
- Maximize Window
- Very often, especially when painting, you will want to expand the window pane to full screen to see and work on the details. Or you can wear out your middle mouse button
- View All
- Scales the image and UVs to fit within the window pane. Sometimes UVs can stray off into the woods, and this helps you find them and bring them back into the image area.
- View Selected
- Centers the view on the selected faces
- Update Automatically
- As you move UVs around, the resulting texture changes on the mesh (shown in the 3D window) are updated as you move around. Otherwise, updates are made when you drop the UVs. Use this option if you have the CPU power.
- View Navigation
- Hotkeys to zoom in and out the display; same as using the MMB wheel. Also note the window can be panned using ⇧ ShiftMMB . There is no rotate or User view, since we are dealing with a 2 dimensional image.
- Draw Shadow Mesh
- Toggles whether to draw an outline of the whole UV Layout for background painting alignment. Very Handy.
- Draw Faces
- When enabled, draws selected faces over the image
- Display Normalized Coordinates
- Displays the UV Coordinates in the Properties panel normalized to 1.0. For example, a UV coordiate with X=64 over a 256 grid would be normalized to 0.25.
- Composite Preview
- A work in progress...
- Curves Tool
- Shows the Combined, Red, Green and Blue (CRBG) Color Curves applet. Select a channel (C, R, B, or G) and adjust the curve to affect the colors of the image.
- Paint Tool
- Shows the Vertex Paint floating window. See Vertex Paint.
- Real-Time Properties
- Shows a floating window which allows you to set Animation and Tile info used in the Game Engine.
- Anim and Tiles - See Using UV Textures
- UV Vertex - Normally, the UV Vertex information is in pixels and the black workspace defaults to 256x256; with an image loaded, this display shows you the UV coordinates in relation to the exact image pixel location. With the menu item Display Normalized Coordinates turned on, the vertex location is scaled to 1.0. Origin is the bottom left hand corner of the black workspace. You can click into the X or Y field and manually set the location of a single UV or the median points of multiple UVs, or use the arrows to adjust their location in increments.
- Many sources can be used for the image portion of the UV Texture. This panel shows you what you are using, and gives you basic controls to select, reload, turn TV interlacing fields on/off (Even or Odd), and do anti-aliasing on the image to smooth the image.
This menu helps you select UVs to work on:
- Linked UVs ; CtrlL
- This menu item selects all UVs that are part of the same UV map. Recall that a map is made for every submesh and seamed part of the mesh, and is analogous to a piece of cloth. Selecting Linked UVs works similarly to the command in 3D View. It will select all UVs that are 'connected' to currently selected UVs.
- Pinned UVs ; ⇧ ShiftP
- You can pin UVs so they don't move between multiple unwrap operations. This menu item selects them all.
- Unlink Selection ; AltL
- Cuts apart the selected UVs from the map. Only those UVs which belong to fully selected faces remain selected following this command. As the name implies, this is particularly useful to unlink faces and move them elsewhere. The hotkey is analogous to the mesh Separate command.
- Select/Deselect All ; A
- Selects or de-selects all UV coordinates. When initially unwrapping, you will want to select All UVs to rotate, scale, and move them around.
- Border Select Pinned ; ⇧ ShiftB
- Use the box lasso to select only pinned UV coordinates.
- Border Select ; B
- Use the box lasso to select normal UV coordinates.
- Active Face Select
- If turned on, when youRMB click a 'face' in the UV map, the corresponding face in the 3D View is highlighted. Use this as a nice way of seeing how the initial unwrap corresponds to your real world to aid in rearranging the map into a coherent layout. In addition, (stay with me here) all four UVs that correspond to that face are selected. Very handy for moving/rotating a whole UV face at a time, instead of individual UVs.
I know, I know, you're anxious to get started painting. Refer to the next section for help on this menu.
This is a long menu that gets cut off sometimes. Here are the UV layout-related choices in the order that they appear:
- Displays the list of Python scripts you have loaded on your PC that do handy things with UV Textures:
- Auto Image Layout if you have one UV Texture for one part of the mesh, and another different UV Texture (map and image) for another part, use this script to merge them together.
- Save UV Face Layout to save a shadow outline of your UV layout; great as a guide layer when using external paint programs. Enable the SVG option to create a file that uses curves.
- Texture Baker and UV Painter are discussed in the next painting section.
- Show/Hide Faces
- Hide and show selected faces. Works the same way as for meshes in the 3D View, allowing you to focus only on certain parts of the layout.
- Proportional Falloff and Proportional Editing
- Same as mesh, and especially useful because often you are moving around a bunch of vertices in a tight space. Hotkey is O. Mousewheel to change the circle of influence, just like mesh editing.
- When you made a seam and unwrapped it, the mesh was cut at the seam into two pieces. Where they were cut apart, there are now two UV vertices for each mesh vertice; one for a corner or side of one UV map, and another for the other. In order to fill in the gaps between pieces, and make one continuous map, you can Weld them back together. Select the two vertices and then Weld them together. Align vertices in either the X or Y direction so that similar vertices line up. The Weld point is about halfway in between the two.
- Occasionally, a UV map will be backwards from your normal way of thinking. This menu option flips the map like a pancake, in either the X or the Y direction.
- Grab/translate (G), scale (S) and rotate (R) selected vertices. Indespensible, and works just like meshes.
- Stitch and Limit Stitch
- Much like the mesh Remove Duplicates function, this function welds together corresponding vertices that are close. Not close as in horseshoes and hand grenades, but close as defined by the Limit. Different parts of a UV map can be stitched if the border UV vertices correspond to the same mesh vertices by using the Stitch command. The Stitch command works joining irregular outlines. Just select the vertices at the border line; if you are using the Stick UVs to Mesh Vertex, then the corresponding coordinates on the other UV Map will also be selected. Stitch (V) snaps together UVs, whatever the distance between them, whereas Limit Stitch (⇧ ShiftV)only welds UVs within a given range (Limit:, 20 pixels by default). Its advantage over Weld is that it prevents UVs, that are supposed to stay separate, from being joined together.
- Minimize Stretch
- Very often, the initial unwrap will have some vertices bunched up right next to some that are spread apart. Much like smoothing out a wrinkled paper, this handy function spreads out bunched up selected vertices. A large face, at an angle to the projection, will result in a small layout. Hence, any image will appear stretched out, like a painting on a balloon. Use this option to relax the stretch a little.
- Pin and Unpin
- Using the Pin (P) command on selected vertices forces them to stay put between multiple unwrap operations, pinned in their current location. Any subsequent Unwraps will not move them. They appear red and larger than other UV coordinates, like a pushpin. Unpin (AltP) sets them free. Read more about it in the #Using_the_Pin_command section.
- Layout Clipped to Image Size
- Keeps the UVs in the corral of the Image size. Prevents you from moving a UV outside the image area.
- Quads Constrained Regular
- Too geeky for me. Sorry. I mean really, those three words just don't go together in any comprehensible way for my tiny brain :) (In fact, I think this means "Quadrangles (are) constrained (to be) regular"…) When enabled and you grab a UV coordinate, it tries to help you make the UV area square or rectangular. Use it when texturing an orthogonal image to a real-world mesh. Warning: it does an automatic unlink from neighbors if they aren't in line as well.
- Snap to Pixels
- Put in here by the developers for the perfectionist in all of us; it causes dropped UVs to snap to an even pixel location, so that the UVs line up perfectly with the image. Exactly. Precisely. NO .126 or .436 or any garbage like that. Nice clean units. Gotta love it.
Iteration and RefinementAt least for common people, we just don't "get it right the first time." It takes building on an idea and iterating our creative process until we reach that magical milestone called "Done." In software development, this is called the Spiral Methodology. Applied to Computer Graphics, we cycle between modeling, texturing, animating, and then back to making some modifications to mesh, re-UV mapping, tweaking the animation, adding a bone or two, finding out we need a few more faces, so back to modeling, etc. We continue going round and round like this until we either run out of time, money, or patience, or, in some rare cases, are actually happy with our results. save an outline of your UV layout. Don't be afraid to try different UV Calculations for the same set of faces to get one that looks good to you and will not be a lot of work to arrange.
TradeoffsFor example, consider the creation of a game character. We want the character to look realistic. Realism in appearance for game characters comes in two parts: shape and texture. Regarding shape, we want the model to look proportioned and smooth, and not too blocky. But the more we smooth it out and add features, the more polygons and faces we have. More polys is bad, because it slows down game play because it taxes computer resources. Texture adds realistic colors to the surface, but again, more detailed images means more pixels and thus taxes compute power again. So, there is a balance between the number of faces and the size of the textures, and acceptable realism and game play. Very early games, for example, had a human head the shape of a blocky cube with a texture of a face; let's just say you had to use your imagination. But, it achieved an acceptable level of realism and had responsive game play on computers available at the time.
Using the Pin command
Developing a game character is thus an iterative creative process. We model the game character, unwrap it, start creating an image for it, and then realize that we have too many faces. We reduce the faces, unwrap again, and start repainting.
This is where the Pin command comes in. The first time we unwrap and start drawing an image (for example the clothes), we want to preserve that work. When we unwrap the second time, we don't want the chest UVs to be mapped somewhere else on the image; we want them to stay right where we put them, right over the painting of the vest. So, before unwrapping the second time, we Pin them, then change the mesh, and unwrap the mesh again. The second time we unwrap, those pinned UVs coordinates will stay in place, no matter what UV Calculation method we use or how we change seams.
The other use of the Pin command is sort of an undo. Imagine that when editing the UV map, you discover that yesterday you accidentally welded five unrelated UV coordinates together by mistake. Undo is therefore not available, and you don't want to have to go back to an old copy. Don't feel stupid; your author did so in generating these examples. So you pin all the coordinates except the welded one, re-unwrap, and the UV coordinates will be 'restored'.
Refining the Layout
Refinement comes into play when we finally look at our character, and realize that we need more detail in a particular spot. For example, areas around the eyes might need crow's feet, or we need to add a logo to the vest. As you start to edit the image, you realize that there just aren't enough pixels available to paint the detail that you want. Your only choice is to expand the size (scale out) that UV face. Using the minimize stretch or scale commands, you expand the UV faces around the eyes or chest, allocating more pixels to those areas, but at the same time taking away pixels (detail) from something else, like the back of the head. After refining the UV map, you then edit the image so that it looks right and contains the details you want.
Reusing TexturesAnother consideration is the need to conserve resources. Each image file is loaded in memory. If you can re-use the same image on different meshes, it saves memory. So, for example, you might want to have a generic 'face' painting, and use that on different characters, but alter the UV map and shape and props (sunglasses) to differentiate. You might want to have a "faded blue jeans" texture, and unwrap just the legs of characters to use that image. It would be good to have a generic skin image, and use that for character's hands, feet, arms, legs, and neck. When modeling a fantasy sword, a small image for a piece of the sword blade would suffice, and you would Reset Unwrap the sword faces to re-use that image down the length of the blade.