Hour 6. Unfolding UVs and Applying Textures

Without materials, your models are going to be gray and lifeless. Maya has state-of-the-art shading tools, and you’ll enjoy the flexibility the program offers. Your objects will get their color, shininess, even reflection from texture maps—image files that are projected or painted onto the surface of your geometry. But before you can apply a texture map to your objects, you have to edit the UVs of your object. What are UVs? Imagine you have a map of the earth and you want to paste it on a globe. If you just try to wrap up the globe inside the map, there’s going to be excess paper hanging off the globe, and it won’t fit correctly. This is where UVs come in. UVs represent the “flattened-out” version of your model, so that textures can be applied correctly. You decide where the seams should be and then essentially unfold the shell to be flat. Take that globe and hammer it flat, and you can simply lay the map on top of it.

In this Hour, you will see a proper UV layout for our hammer model, and how to get there. You will learn how we decide on material properties, and how to load textures into the appropriate slots. After all, the final quality of a 3D object is dependent at least 50% on the quality of the texture in conjunction with the geometric detail.

Now let’s look at how UVs actually work. Figure 6.2 shows a sphere with something called a “ramp” texture already applied. Ramp textures let you apply a gradient shading look to your objects. In this figure, you can see the association between the gradient colors on the object and the gradient colors in the UV Texture Editor. You can see the seam that is created by the UV border, and hopefully the concept of the “flattened-out” object will become very clear (see Figure 6.2).

With a texture applied, UVs become a lot more easy to understand. You can see the colors wrapped around this mesh as well as how the UVs line up in the UV Texture Editor.

However, the UVs do not look nicely laid out as they do with the primitive sphere. It is up to you to create UVs and make them look nice on your custom models. Figure 6.3 shows the poorly laid-out UVs on the hammer model.

A common workflow to create nicely laid-out UVs is to begin with an automatically created UV set and then manually adjust the UVs in the UV Texture Editor to fit your model. To begin working with an object’s UVs, press F3 to get to the Polygons menu set and then go to the Create UVs menu. You will see a host of choices. In general, choose a mapping shape that matches your object roughly. A sphere will use spherical; a lamppost should be cylindrical. Automatic Mapping creates a series of cuts (seams) to make it so that the least amount of distortion occurs when applying your texture. You can’t depend on Maya’s automatic UV mapping to give you perfect results, but it will add UVs to the model that can be changed later. The exception to the rule of using a UV projection shape that is close to your model shape is if you have an object that is symmetrical, like ours:

In the case of symmetry, you want to use Planar, so click Create UVs, Planar (remember, the symbol means you will be opening a tool’s options before applying).

Set the projection axis to Project From the Z Axis. Leave the rest of the options at their defaults for now and click Apply.

After you have applied automatic mapping to your object, you next must decide where the texture seams are going to be on your model. With a model that is symmetrical like this hammer, it makes sense that both sides should have the same texture. That means the UV seam can be right down the middle along the center edge loop that exists.

The two commands you absolutely need to know about (in the UV Texture Editor) are the Polygons, Cut UV Edges command and the Polygons, Sew UV Edges command, shown in Figure 6.4.

Using these two commands in conjunction with the Move and UV Smooth tools in the UV Texture Editor will get you 90% of the way there. Now follow these steps:

Switch to Edge component mode by RMB clicking on your object in the panel and dragging upward. Select the new edge loop that runs up the center of the hammer in your perspective panel. You can do this by Shift+LMB clicking on each edge, double-clicking on a single edge in the edge loop (preferred method), or selecting a single edge loop and pressing the left arrow key on your keyboard.

In the UV Texture Editor, go to Polygons, Cut UV Edges. Then select all the other edges besides the center edge loop. (You can quickly do this by holding down Shift and dragging a selection box around the entire hammer in the Persp panel. This toggles the selection and therefore will invert the selected edges.)

Back in the UV Texture Editor, click Polygons, Sew UV Edges.

Select the center edge loop one more time. Pressing Ctrl+RMB in the UV Texture Editor brings up a marking menu to convert your selection from one component type to another (from faces to vertices, or in this case, edges to UVs). This marking menu is available at all times and not just when you’re working with UVs. Convert your selection to UVs, as shown in Figure 6.5.

Now if we use the Smooth UV tool, the UVs in this middle seam will move out from behind the other UVs and get some UV space for themselves, as in Figure 6.6.

Now that you understand how to arrange our UVs nicely, let’s apply a custom texture and use some of Maya’s great texturing tools.

The Hypershade is the main menu that deals with texturing. To access the Hypershade, go to Windows, Rendering Editors, Hypershade (see Figure 6.7).

When you are connecting nodes together and building what are called “shading networks,” you will primarily be using the Work Area. By default, every object is assigned the gray lambert shader called lambert1 when it is created. All of the objects we create in Maya will need custom materials, so let’s start by creating a new material for our hammer.

With the Hypershade open, we can start creating some materials. You can follow this procedure to create nearly infinite combinations of materials in the Hypershade, but I’ll show you how to put nodes together to make the hammer have some nicer material properties to it. First thing we’ll do is create a Blinn material. Blinn is a material that has reflectivity and a specular highlight to it. It comes standard with most 3D programs. When you click on Blinn, the newly created node appears in the Work Area. Double-clicking any node in the Hypershade opens that node in the Attribute Editor, as shown in Figure 6.8.

Scrolling down the menus in the Attribute Editor reveals the great control Maya gives you over the look of your materials. Let’s take a brief look at some of the material options, and go over what each one does. Most of the options are the same or similar for your standard materials.

Color—This channel is normally your main concern. It is what it sounds like—the color of the texture. Whether it is a Maya checker texture or a File node (the way to load your own images as textures), you can load almost any node into this channel.

Transparency—This channel controls how see-through your material is. It determines the amount of transparency by black (value of 0) being completely opaque and white (value of 1) being totally clear. If you are using raytraced shadows, the shadow will be affected by this channel as well (more on shadows in Hour 19, “Lighting Your Scene Correctly”). You can use this channel to make “holes” in your material also, like a tattered pirate’s flag for example.

Ambient Color—This channel lightens and blends the color attribute with the color chosen here. If there are ambient lights in your scene, they will determine how this channel contributes to the final color of your texture.

Incandescence—This channel makes the object appear to have a light source emitting from within it. Although it won’t actually emit light from its surface when this attribute is used, it will appear to. The difference between Ambient Color and Incandescence is this: An Ambient Color of white will make an object in total darkness render its pure color channel, whereas an Incandescence of white will make the same object pure white (totally unaffected by shadow).

Bump Mapping—This channel adds surface relief at render time. You can create the effect of subtle grain to your surfaces, or maybe small details such as rivets in metal, stitching in clothing, and so on. The surface is not actually displaced; bump mapping only gives the illusion that it is.

Diffuse—Diffuse is the power of the reflection of light, put simply. Because we only see an object by the light that reflects off of that object back into our eye, changing the diffuse value is like raising and lowering the amount of light an object reflects. In turn, the Color value is affected by brightening and darkening. In a way, it’s the opposite of Ambient—at 1.0, Diffuse will make the object render at brightest its pure Color value when not in shadow, and at 0.0, it will render black regardless of the lights in the scene.

Translucence—The amount of light that passes through an object. This can be used to simulate surfaces that have light diffusing through them, such as wax, paper, leaves, and so on. The simplest way to describe the effect of adding translucency is to think of a thin object such as a leaf that has a shadow being cast on the bright side, and being able to see that shadow on the other side of the leaf (see Figure 6.10).

Translucence Depth—Controls the way the light travels through the object by using a distance value.

Translucence Focus—This controls how much the light is scattered in all directions or focused as it is transmitted through the surface. A low value is recommended for very thin objects such as paper where the shadows are going to be fairly sharp on the other side of the object. A high value is good for objects such as wax because the light truly spreads out very widely as it enters this material.

Notice how the shadow that the sphere is casting on the right plane can be seen from the back of the plane as if it is a piece of thin paper or a leaf. Also notice how the shadow on the ground is not affected (only transparency affects shadow color).

Anisotropic—This material has specular and reflection, but uses an algorithm than warps the specular highlight the way a brushed steel kettle would.

Blinn—This material is a good standard material for shiny and reflective objects. You can get a good range of plastic to metal materials using Blinns.

Hair Tube Shader—This material is useful for application on hair, due to its extremely warped specular highlight that simulates the way hair reflects light.

Lambert—This material is good for objects that do not reflect or have any shininess to them and therefore don’t need a specular highlight. Good examples would be clay and dirt.

Layered Shader—To combine multiple shaders into one, you can use the layered shader. For instance, you can apply a Blinn’s specular highlight to a Lambert’s color to create the texture of dirt in a glass jar.

Ocean Shader—This is a dynamic material that creates an animate ocean. The default settings create a simple, attractive water that is a good launch point for more advanced FX.

Phong—Very much like the Blinn, the Phong shader is good for objects with shininess. The Phong specular highlight algorithm is geared a little bit more toward plastics.

Phong E—The same as Phong, but with added control over the specular highlights.

Ramp Shader—This powerful shader is useful for creating gradient effects based on properties of the scene. You can make the edges of objects a different color based on the angle the surface is relative to the camera, or you can make a stark two-tone color gradient for areas of shadow and light to simulate a cartoon render.

Shading Map—This is a shader that mixes different shaders together, sort of like a Layered Shader, but uses properties such as the color and brightness of shaders to determine how they are mixed together rather than their transparency. It is not very commonly used.

Surface Shader—This is a very commonly used material; it’s a simple way to load color, alpha, and transparency to other channels in Maya. The color will always display pure no matter what the lighting condition.

Use Background—This is an extremely useful shader; it displays whatever background is in your scene—be it a color or an image plane. This material is commonly employed when rendering effects for film and television, or for creating shadow renders for compositing.

Selecting File creates a file node, which is how we load our images as textures. Click the folder icon in the file1 attribute panel to open an explorer window to browse for the textures we’ve created for this hammer (see Figure 6.12).

Navigate to the Hour 6 directory where the hammer’s image maps are found and choose hammer_Color.tga for the color. Select the Blinn in the Hypershade one more time so we can load another map into its attributes. Click on the “specular color” map button and choose “file” one more time. In the new file node, click the browse button and choose hammer_specColor.tga. This file has a white value on the metal parts and a black value on the handle area—to make it so there is no specular highlight on what is supposed to be the soft rubber grip. Figure 6.13 shows the hammer with the material edited to be more like rubber.

A. You can wait until a model is finished to create its UVs, or if you don’t want to have to remember to use a certain mapping type and so on, you can create and edit UVs as you go along. Manipulating geometry will not mess up already created and edited UVs, but it might create new UVs that get in the way of your customized ones.

Q. Can an object have more than one UV set?

A. Yes, you can add as many UV sets as you want to an object by going to the Create UVs menu and selecting Create Empty UV set. An instance when this might be useful is if you want a character’s face to have a different material than his clothes, and you create a UV set for just his head.

Q. The UV Texture Editor is square. What do I do if my texture is not square?

A. You should be using square textures as a rule because of this reason, but if you absolutely can’t, you can always resize the UVs to match the texture as it shows up in the UV Texture Editor.

Q. Can I apply more than one material to an object?

A. Certainly, and there are a few ways to do this. Let’s say you want to use two different materials for the hammer (the metal part and grip). The easiest way is to RMB click and drag your mouse, choose “face” and select the faces you want to apply the new material to, and then MMB drag the material from the Hypershade onto these faces. You can also use a Layered shader and use an image as a mask to determine where the two materials are going to show up on the object.

2. What two tools do you use to create the seams in your UVs?

3. What material type would be the best for a nonreflective surface such as a tablecloth?

4. What material attribute controls how “see-through” an object is?

5. How do you create a new material in the Hypershade?

Open the Hypershade and create an appropriate material. Depending on the object you’ve made, load your texture file into the color attribute of your material. Finally, drag the material onto the object to apply it.

2. The Cut UV Edges tool and the Sew UV Edges tool allow you to create the seams in your UVs so that the object can be flattened out nicely in the UV Texture Editor.

3. Lambert materials are good for objects with no shininess.

4. Transparency is the attribute that makes an object see-through. Do not confuse this with translucency, which creates the effect of light passing through an object.

5. The Create pane on the left side of the Hypershade houses all the buttons of material nodes you can use to build shading networks. Clicking on any one of these will create that node and place it in the Work Area.