The most common shader type is Lambert, an evenly-diffused shading type found in dull or matte surfaces. A sheet of paper, for example, is a Lambert surface.

A Lambert surface diffuses and scatters light evenly across its surface, in all directions. (See Figure 7.2.)

Figure 7.4. A Blinn shader

Phong shading, named after its developer, Bui Tuong-Phong who created it in 1975, brings to a surface's rendering the notions of specular highlight and reflectivity. A Phong surface reflects light with a sharp hot spot, creating a specular highlight that drops off sharply. (See Figure 7.3.) You'll find that glossy objects such as plastics, glass, and most metals take well to Phong shading.

Also named after its developer, James Blinn, the Blinn shading method brings to the surface a highly accurate specular lighting model that offers superior control over the specular's appearance. (See Figure 7.4.) A Blinn surface reflects light with a hot spot, creating a specular that diffuses somewhat more gradually than a Phong. This creates a shader that is good for use on shiny surfaces and metallic surfaces.

The Phong E shader type expands the Phong shading model to include more control over the specular highlight. A Phong E surface reflects light much as a regular Phong does, but it has more detailed control over the specular settings to adjust the glossiness of the surface. (See Figure 7.5.) This creates a surface with a specular that drops off more gradually and yet remains sharper than a Blinn. Phong E also has greater color control over the specular than do Phong and Blinn, giving you some more options for metallic reflections.

Figure 7.5. A Phong E shader

The Anisotropic shader is good to use on surfaces that are deformed, such as a foil wrapper or warped plastic. (See Figure 7.6.)

Figure 7.6. An Anisotropic shader

Anisotropic refers to something whose properties differ according to direction. An Anisotropic surface reflects light unevenly and creates an irregular-shaped specular highlight that is good for representing surfaces with directional grooves, like CDs. This creates a specular highlight that is uneven across the surface, changing according to the direction you specify on the surface. By contrast with Blinn and Phong types, the specular highlight is evenly distributed to make a circular highlight on the surface.

A Layered shader allows the stacking of shaders to create complex shading effects, which is useful for creating objects composed of multiple materials. (See Figure 7.7.) By using the Layered shader to texture different materials on different parts of the object, you can avoid using excess geometry.

Figure 7.7. A Layered shader

You control Layered shaders by using transparency maps to define which areas show which layers of the shader. You drag material nodes into the top area of the Attribute Editor and stack them from left to right, the left being the topmost layer assigned to the surface.

Layered shaders are valuable resources to control compound and complex shaders. They are perfect for putting labels on objects or adding dirt to aged surfaces. You will use a Layered shader in the Axe Texturing exercise later in this chapter.

A Ramp texture is a gradient that can be attached to almost any attribute of a shader as a texture node. Ramps can create smooth transitions between colors and can even be used to control particles. (See Chapter 12, "Maya Dynamics and Effects," for how a ramp is used to control particles.) When used as a texture, a ramp can be connected to any attribute of a shader to create graduating color scales, transparency effects, increasing glow effects, and so on. You will use Ramp textures later in this chapter.

Figure 7.8. A Ramp shader in its Attribute Editor

The Ramp shader is a self-contained shader node that automatically has several Ramp texture nodes attached to its attributes. These ramps are attached within the shader itself, so there is no need to connect external Ramp texture nodes. This makes for a simplified editing environment for the shader because all the colors and handles are accessible through the Ramp shader's own Attribute Editor, as shown in Figure 7.8.

To create a new color in any one of the horizontal ramps, click in the swatch to create a new ramp position. Edit its color through its Selected Color swatch. You can move the position by grabbing the circle right above the ramp and dragging left or right. To delete a color, click the box beneath it.

Ramp textures are automatically attached to the Color, Transparency, Incandescence, Specular Color, Reflectivity, and Environment attributes of a Ramp shader. In addition, a special curve ramp is attached to the Specular Roll Off to allow for more precise control over how the specular highlight diminishes over the surface.

First, set up your render parameters so that you can render out your axe while you are tweaking the Metal shader to get it right.

Figure 7.16. The axe head before and after a reflection is added

Figure 7.17. Use placement nodes in the scene to scale and position textures.

After you create the Env Chrome texture, you'll see a green object in the Modeling windows at the origin, as shown in Figure 7.17. This is the Env Chrome's placement node. You can manipulate this node just as you manipulate other Maya objects—in other words, move, rotate, and scale it.

Altering this will change how the environment chrome projects itself in the scene. For example, if you increase the size of this placement node, the grid showing in the reflection of the axe will get larger. For more on projections and placement nodes, see the "Texture Nodes" section later in this chapter.

A glossy cherrywood would look good for the handle, so a Phong shader would be best.

Figure 7.18. The Wood texture in its Attribute Editor

Currently, the entire length of the handle is shaded as wood, including the top spike. The spike on the axe head should be metal like the axe head.

Figure 7.24. The Layered shader in the Attribute Editor

You can approach this in two ways: with geometry or with shaders. If you manipulate geometry, you select a horizontal isoparm and detach the spike portion of the handle to make it a separate surface. You then assign a Metal shader to the new tip surface.

Using a shader instead of cutting up or creating more geometry can be desirable in many instances. For example, you may not be able to detach surfaces like this all the time.

The Layered shader is a normal surface shader that allows you to stack materials on top of each other to assign to a surface. You control which layer of material is exposed and by how much by assigning transparency values or textures to each layer. Use a Ramp texture to specify where on the handle the wood stops and the metal starts.

To create a Layered shader, follow these steps:

The file axe_texture_C.mb, in the Scenes folder of the Axe project on the CD, has the final textured axe for your reference.

Now you have a fully textured axe. Because you used a Layered shader, you did not need to build another piece of geometry to represent a metal tip. You can embellish a model a lot at the texturing level. Although you may first consider using geometry, you can accomplish a number of tasks by using simple texturing tricks, such as those you used for the axe handle and its metal spike. The more you explore and experience shaders and modeling, the better you'll be at juggling modeling with texturing to get the most effective solution.

We will begin texturing the Red Wagon from Chapter 6, "Building the Red Wagon," later in this chapter and take it into lighting in Chapter 10. However, for even more practice, try loading the locomotive model from Chapter 4, "Beginning Polygonal Modeling," and texturing it from top to bottom. A great deal of independent geometry needs textures, some of which must be carefully placed with 3D placement nodes. Experiment with as many different ways of shading the locomotive as you can figure out.

UV mapping places the texture directly on the surface and uses the surface coordinates for its positioning. In this case, you must do a lot of work to line up the UVs on the surface to make sure the created images line up properly. What follows is a brief summary of how UV mapping works. You will get hands-on experience with UV layout with the Red Wagon later in this chapter.

Just as 3D space is based on coordinates in XYZ, surfaces have coordinates denoted by U and V values along a 2D coordinate system for width and height. The UV value helps a texture position itself on the surface. The U and V values range from 0 to 1, with (0,0) UV being the origin point of the surface.

Figure 7.29. Selecting the type of map layout

Maya creates UVs for primitive surfaces automatically, but frequently you need to edit UVs for proper texture placement, particularly on polygonal meshes once you have edited them. In some instances, placing textures on a poly mesh will require projecting the textures onto the mesh because the poly UVs may not line up as expected once the mesh has been edited. See the next section, "Using Projections."

Figure 7.30. The projection node in the Attribute Editor

If the placement of your texture or image is not quite right, simply use the 2D placement node of the texture node to position it properly. See the section "Texture Nodes" later in this chapter for more information.

You need to place textures on the surface. You can often do so using UV placement, but some textures need to be projected onto the surface. It is common to project textures (when texturing polys, for example). A projection is what it sounds like. The file image, ramp, or other texture being used can be "beamed" onto the object in several ways.

You can create any texture node as either a normal UV map or a projected texture. In the Create Render Node window, select the method—Normal (for UV mapping) or As Projection—by clicking the appropriate radio button before you create the texture. (See Figure 7.29).

When you create a projected texture, a new node is attached to the texture node. This projection node controls the method of projection with an attached 3D placement node, which you saw in the Axe exercise. Select the projection node to set the type of projection in the Attribute Editor. (See Figure 7.30.)

Setting the projection type will allow you to project an image or a texture without having it warp and distort, depending on the model you are mapping. For example, a planar projection on a sphere will warp the edges of the image as they stretch into infinity on the sides of the sphere.

Now try removing the color map from the Blinn shader. In the Blinn shader's Attribute Editor, right-click and hold the attribute's title word Color, and then choose Break Connection from the shortcut menu. This severs the connection to the checker and resets the color to gray. Now re-create a new checker map for the color, but this time create it as a projection. In the illustration on the left in Figure 7.32, you see the perspective view in Texture mode (press the 6 key) with the two objects and the planar projection placement node.

Try moving the planar placement object around in the scene to see how the texture maps itself to the objects. Figure 7.32 on the right shows the rendered objects.

Try the other projection types to see how they affect the texture being mapped.

Figure 7.32. A planar projection checkerboard in the view panel (left) and rendered (right)

Figure 7.33. The spherical projection's Manipulator tool

Projection placement nodes control how the projection maps its image or texture onto the surface. Using a NURBS sphere with a spherical projected checker, with U and V wrap turned off on the checker texture, you can see how manipulating the place3dTexture node affects the texture.

In addition to the Move, Rotate, and Scale tools, you can use the Special Manipulator tool (press T to activate or click the Show Manipulator Tool icon in the toolbar) to adjust the placement. Figure 7.33 shows this tool for a spherical projection.

Drag the handles on the special manipulator to change the coverage of the projection, orientation, size, and so forth. All projection types have special manipulators. Figure 7.34 shows the special manipulator wrapping the checker in a thin band all the way around the sphere.

Figure 7.34. The manipulator wrapping the Checker texture around the sphere (left, perspective view; right, rendered view)

To summarize, projection textures depend on a projector node to position the texture onto the geometry.

You can create a number of texture nodes in Maya. This section covers the most important. All texture nodes, however, have common attributes that affect their final look. Open the Attribute Editor for any texture node. (See Figure 7.35.) The two top sections affect the color balance of the texture. The Color Balance and Effects sections are described here.

Figure 7.35. Some common attributes for all texture nodes

Place2dTexture Nodes

2D texture nodes come with a 2D placement node that controls their repetition, rotation, size, offset, and so on. Adjust the setting in this node of your 2D texture in the Attribute Editor, as shown in Figure 7.36, to position it within the Shader network. You used a similar approach when dealing with the wood's 3D placement node in the Axe exercise earlier this chapter.

Figure 7.36. A 2D placement node in the Attribute Editor

The Repeat UV setting controls how many times the texture is repeated on whatever shader attribute it is connected to, such as color. The higher the wrap values, the smaller the texture will appear but the more times it will appear on the surface.

The Wrap U and Wrap V check boxes allow the texture to wrap around the edges of their limits to repeat. When they are turned off, the texture will appear only once and the rest of the surface will be the color of the Default Color attribute found in the texture node itself.

The Mirror U and Mirror V settings allow the texture to mirror itself when it repeats. The Coverage, Translate Frame, and Rotate Frame settings control where the image is mapped. They are useful for positioning a digital image or a scanned picture.

Figure 7.37. The Ramp texture

Importing an Image File as a Texture

To attach an image to the Color attribute of a Lambert shader for example, follow these steps:

Figure 7.38. The File texture node

1. Create the Lambert shader. (Phong, Blinn, or any of the shaders will do.)

2. Click the Map button to map a texture on the Color attribute of the new Lambert shader. Select the file node as a normal texture. (You can also use a projected texture with an image file.) The Attribute Editor will show the attribute for the file node. See Figure 7.38.

3. Next to the Image Name attribute, click the Folder icon to open the file browser. Find the image file of choice on your computer. (It's best to put images to use as textures in the Sourceimages folder of the project. As a matter of fact, the file browser will default directly to the Sourceimages folder of your current project.) Double-click the file to load it.

4. After you import the image file, it connects to the Color attribute of that shader and also automatically connects the alpha to "transparency" if there is an alpha channel in the image. You can position it as you please by using its Place2dTexture node, or by manipulating the projection node if you created the File texture node as a projection.

   You can attach an image file to any attribute of a shader that is mappable, meaning it is able to accept a texture node. Frequently, image files are used for the color of a shader as well as for bump and transparency maps. You can replace the image file by double-clicking the File texture node in the Hypershade and choosing another image file with the file browser. Maya disconnects the current image file and connects the new file.

Using Photoshop Files: The PSD File Node

Maya can also use Adobe Photoshop PSD files as image files in creating Shading networks. The advantage to using PSD files is that you can specify the layers within the Photoshop file to different attributes of the shader as opposed to importing several image files to map onto each shader attribute separately. This, of course, requires a modest knowledge of Photoshop and some experience with Maya shading. As you learn how to shade with Maya, you will come to appreciate the enhancements inherent in using Photoshop networks.

Try This

You will create a single Photoshop file that will shade this sphere with color as well as transparency and a bump. Again, this is instead of creating three different image files (such as TIFFs) for each of those shading attributes.

Figure 7.39. The Create PSD Network Options window

1. Create a NURBS sphere in a new scene, and assign a new Lambert shader to it. You can do this through the Hypershade or the Multilister, or by choosing Lighting/Shading → Assign New Material → Lambert in the Rendering menu set. This creates a new shader and assigns it to the selection, in this case your sphere.

2. Select the sphere, and choose Texturing → Create PSD Network. In the option box that opens, select color, transparency, and bump from the list of attributes on the left side and click the right arrow to move them to the Selected Attributes list on the right, as shown in Figure 7.39.

3. Select a location and filename for the image. By default, Maya will place the PSD file it generates under the Sourceimages folder of your current project, named after the surface it to which it applies. Click Create.

4. In Photoshop, open the newly created PSD file and you'll see three layers grouped under three folders named after the shader attributes you selected when creating the PSD file. There will be a folder for lambert2.bump, lambert2.transparency, and lambert2.color, as well as a layer called UVSnapShot. The UVSnapShot layer gives you a wireframe layout of the UVs on the sphere as a guideline to paint your textures. Because the sphere is an easy model, you won't need this layer, so turn it off. You will use UVSnapShots later in this chapter. You can now paint whatever image you want into each of the layers to create maps for each of the shader attributes, all in one convenient file. Save the PSD file. You can save over it or create a new filename for the painted file.

   

   Figure 7.40. The PSD network for the Lambert shader in the Hypershade shows the connections to color, bump, and transparency.

5. In Maya, open the Hypershade and open the Attribute Editor for the Lambert shader assigned to the sphere (in this case, Lambert2). If you graph the connections to the Lambert shader in the Hypershade windows work panel, you'll see that the PSD file you generated is already connected to the color, bump, and transparency attributes of the shader, with the proper layering all set for you as shown in Figure 7.40.

6. Open the file nodes for the shader and replace the PSD file with your new painted PSD file. If you saved your PSD file with the same name, all you need to do is click the Reload button to update the psdFilenode.

If you decide that you need another attribute added to the PSD file's layering, or if you need to remove an attribute, you can edit the PSD network. Select the shader in the Hypershade and choose Edit → Edit PSD Network. In the Options window, you can select new attributes to assign to the PSD file, or you can remove existing attributes and their corresponding Photoshop layer groups. Once you click Apply or Edit, Maya saves over the PSD file with the new layout.

Disconnecting a Texture

Sometimes the texture you've applied to an object is not what you want and you need to remove it from the shader. To do so, double-click the shader in the Hypershade to open its Attribute Editor.

You can then disconnect an image file, or any other texture node from the shader's attribute, by right-clicking the attribute's name in the Attribute Editor and choosing Break Connection from the context menu as shown in Figure 7.41.

Figure 7.41. Right-clicking on a shader's attribute allows you to disconnect a texture node from the shader.

Load the file RedWagonModel_v08.ma from the Scenes folder of the RedWagon project to begin shading the finished model of the wagon.

If perhaps you skipped Chapter 6—or haven't memorized that entire chapter yet—and are not familiar with this model, take a few moments to familiarize yourself with the geometry in the wagon and how it is modeled. Study the color images of the wagon and see how light reflects off its plastic, metal, and wood surfaces. Blinn shaders will be perfect for nearly all the parts of the wagon.

Figure 7.43. Create the four-colored Blinn shaders.

Initial Assignments

Take a look at the photo of the wagon in the Color Section in the middle of this book. The bullnose and tires are black, the wheel rims are white, the floor is blue, the screws and bolts and handlebar are chrome metal, the railings are wood, and the main body is red. Assign shaders to the wagon according to the color photo and the following steps:

1. In the view panel, select the side panels (the A and B panels, without the screws and bolts) and the wheel rim caps as shown in Figure 7.44, and assign the red Blinn shader to them. Press 6 to enter into Texture Display mode.

2. Select the wheelMesh objects for all four wheels and assign them the White shader. The tires will also turn white, but we will fix that in just a little bit, so don't worry about it now. See Figure 7.45.

   

   Figure 7.44. Assign the Red shader.

   

   Figure 7.45. Assign the White shader.

3. Select the bullnose (the rounded cylinder in front of the wagon) and assign it the black Blinn.

4. Select the wagon floor object and assign it the Red shader, as shown in Figure 7.46. You'll notice that the front and back body of the wagon turn red as they are supposed to, but so does the floor of the wagon, which should be blue according to the photo in the Color Section. If you try to assign the Blue shader to the wagon floor mesh, the floor will be correct, but the front and back body of the wagon will be blue and not red. We will fix this later.

Now we have initial assignments for the basic colors of the wagon's body. Let's tweak these shaders' colors next.

Figure 7.46. Assign the Red shader to the wagon floor for now.

Refer to Figure 7.47 to observe how the materials are different between the rim and the tire for the wheels. The rim is glossier and has a tighter, sharper specular, while the tire has a very diffuse specular and is quite bumpy. As we did for the Axe exercise, we will create a Layered shader for the wheels with white feeding into the rim portion and black into the tire.

Figure 7.47. The tire on the wagon

Coloring the Wheel

First, we need to determine where the white ends and the black starts on the surface of the wheel mesh.

1. Select the White shader in the Hypershade window. Click the Map button (

   
   

   Figure 7.48. The Ramp texture displays on the wheel.

   Note

   If the ramp does not show up in your view panels, make sure you press 6 to enter Texture Display mode. If the colors and ramp texture still do not display, make sure that Use Default Material is not checked in the view panel's Shading menu.

2. The ramp is running the wrong way; we need the gradient to run from the center to the edge, and not clockwise across the wheel. In the Ramp texture's Attribute Editor, set the Type to U Ramp as shown in Figure 7.49.

3. Now the color gradient should be running from the center (red) to the outside edge (green) to blue on the reverse side of the wheel. Move the blue ramp's handle in the ramp's Attribute Editor until its Selected Position value is about 0.6, as shown inFigure 7.50.

   

   Figure 7.49. Set the ramp to a U Ramp type.

   

   Figure 7.50. Move the blue handle.

   

   Figure 7.51. The White shader has the ramp attached as color.

4. Delete the red handle in the ramp by clicking on the checked box on the right of the handle. Change the blue color to black and the green color to white. Name this ramp wheelPositionRamp. Now that we have pinpointed where the white rim ends and the black tire begins, we will use this ramp to place the Tire shader on top of the Rim shader in the Layered shader that we will eventually create.

   

   Figure 7.52. Disconnect the ramp from the Color attribute.

5. We do not need this Ramp shader on the color of the shader anymore—we did this so we could easily see the ramp color positions in the view panels. In the Hypershade, select the White shader and click the Input and Output Connections icon (

   
   

   Figure 7.53. Drag the White shader to the Layered shader, and delete the default Green shader from it.

6. In the Attribute Editor, RMB+click on the Color attribute and select Break Connection from the context menu to disconnect the ramp from the color. (See Figure 7.52.) Set the Color back to white. Notice that the link connecting the Ramp texture node to the White shader node disappears in the Hypershade window.

7. Create a Layered shader. MMB+drag the White shader from the Hypershade to the Layered Shader Attributes window, as shown in Figure 7.53. Delete the default Green shader in the Attribute Editor by clicking the checked box below its swatch.

8. Create a new Blinn shader, and set its color to black. Name the shader tireShader. Select the Layered Shader and then MMB+drag the new tireShader from the Hypershade to the Layered Shader's Attribute Editor, placing it to the left of the White shader, as shown in Figure 7.54. Name the Layered Shader wheelShader.

   

   Figure 7.54. Add the black tireShader.

   

   Figure 7.55. The wheels are still all white.

9. Select the wheels and assign the wheelShader Layered shader to them. The wheels should turn gray in your view panels. Layered shaders typically do not display in panels, so you will have to render a test frame. Render the persp panel, and your tire should look all white (except for the red cap). This is where the ramp we created earlier (wheelPositionRamp) comes into play. Figure 7.55 shows the all-white wheels.

10. Select the wheelShader, and click Input and Output Connections to graph the network in the Work Area of the Hypershade window. In the top panel of the Hypershade, click the Texture tab to display the texture nodes in the scene.

11. In the wheelShader's Attribute Editor, click on the tireShader swatch. MMB+drag the wheelPositionRamp node to the Transparency attribute, as shown in Figure 7.56.

    

    Figure 7.56. Attach the ramp to the transparency of the tireShader in the wheelShader.

    

    Figure 7.57. The tires are not quite done; the backs are all black.

12. Once you attach the ramp, the wheelShader icon turns white on top and black on the bottom. Render a frame in the persp panel. See Figure 7.57.

13. We need to add another white handle to the transparency ramp, so we can make the back rims white again. In the Hypershade, double-click the ramp to open the Attribute Editor. Add another color handle to the ramp, and set its color to white, as shown in Figure 7.58. The color of the wheel gets really weird now.

14. The gradient on the wheels looks wrong again. This is because the gradient in the ramp is set to linear, so the black area slowly grades to white. We need to better define that. In the ramp's Attribute Editor, set the Interpolation to None, as shown in Figure 7.59. Move that second white handle to place the white rim on the back of the wheel, and we're done coloring the wheel!

Figure 7.58. Adding another white handle to the ramp

Figure 7.59. Set the ramp's Interpolation to None.

Setting the Feel for the Materials

Because the material look and feel on the real wheels differs quite a bit between the rim and the tire, we will have to tweak both the White Rim shader and the Black Tire shader. Again, the rim is a smooth, glossy white, and the tire is a bumpy black with a broad specular.

1. Let's set up a good angle of view for our test renders. Position your persp view to resemble the view in Figure 7.60. Render a frame.

2. Select the White shader and set the Eccentricity to 0.05 and the Specular Roll Off to 0.5. This will sharpen the specular highlight on the rim.

3. Select the black tireShader, and set the Eccentricity to 0.375 and the Specular Roll Off to 0.6 to make the highlight more diffuse across the tire. Set the Reflectivity to 0.05. Render a frame and refer to Figure 7.61.

Figure 7.60. Set your view to this angle and render a frame.

Figure 7.61. Setting specular levels

Creating a Bump

Now let's add a bump to the Tire shader to match the feel of the tire in Figure 7.47 earlier in the chapter.

Figure 7.62. Argh! The whole wheel becomes bumpy!

1. Open the Attribute Editor for the tireShader, and click the Map icon (

   

2. In the Create Render Node window, check Normal and click to create a Fractal texture map. Notice that the entire wheelShader icon becomes bumpy. (See Figure 7.62.) Render a frame, and you'll see that the entire wheel is bumpy—not just the tire! Argh!

3. We have to use the wheelPositionRamp to prevent the bump from showing on the rim. Select the wheelShader, and click the Input and Output Connections icon (

   

   Note

   Notice the single, blue connecting line between the fractal1 node and the bump2d1 node in the Hypershade. This means the alpha channel of the fractal feeds the amount of bump that will be rendered on the tireShader. We have to alter the alpha coming out of the fractal node with the positioning ramp to block the rim from having any bump at all. The white areas of the ramp will allow an output in alpha from the fractal, which creates a bump for the surface; whereas the black area of the ramp will keep any bump from appearing. Because we already used this ramp to position the Rim shader and the Tire shader on the wheel, it will work perfectly for the bump position as well.

   

   Figure 7.63. Graph the wheelShader network.

4. Select the fractal to display it in the Attribute Editor, and MMB+drag the wheelPositionRamp in the Hypershade to the Alpha Gain attribute for the fractal, as shown in Figure 7.64.

   

   Figure 7.64. MMB+drag the ramp to the Alpha Gain of the fractal.

5. Render a frame, and you will see that now the tire has no bump and the rim is bumpy (Figure 7.65).

6. This is easy enough to fix. All we need to do is reverse the ramp and then feed it into the Alpha Gain of the fractal so that the tire is bumpy and the rim is smooth. In the Hypershade, scroll down the Create Maya Nodes pane on the left all the way down to the section heading called General Utilities. Expand it if it is closed, and click on the Reverse icon to create a reverse node in the Hypershade window. See Figure 7.66.

7. In the Hypershade, MMB+drag the wheelPositionRamp node onto the Reverse node and select Input from the context menu when you release the mouse button. This will connect the output of the ramp into the reverse node, which will essentially reverse the ramp.

   

   Figure 7.65. The tire is smooth and now the rim is bumpy!

   

   Figure 7.66. Create a reverse node.

   

   Figure 7.67. Connecting the reverse node to the fractal node

   

   Figure 7.68. Set the Quality to Production Quality.

8. MMB+drag the reverse node on top of the fractal1 node and select Other from the context menu. This will open the Connection Editor, which you first saw in Chapter 3 in the User Interface. On the left is loaded the reverse1 node, and on the right is the fractal1 node. In the left pane, click the plus sign next to the output entry and select output.X. In the right pane, select the alphaGain attribute, as shown in Figure 7.67.

9. Open the Render Settings window by choosing Window → Rendering Editors → Render Settings. Click on the Maya Software tab, and set the Quality to Production Quality in the pull-down menu. (See Figure 7.68.) Render a frame, and you'll see that we finally have a bump on the tire and a smooth rim! See Figure 7.69.

   

   Figure 7.69. Now we've got the bump where we need it!

10. It's not a very convincing bump yet, so select the fractal node and set the Ratio to 0.85. Click the Placement tab for the fractal (it should be called something like place2dTexture6), and set the Repeat UV values to 18 and 48, as shown in Figure 7.70. This will make the fractal pattern finely speckled on the tire.

11. Render a frame, and the fractal's scale on the bumpy tire looks too strong. Double-click on the bump2d node in the Hypershade and, in the Attribute Editor, set the Bump Depth to 0.1. Render and check your frame against Figure 7.71. The bump looks much better, if not a little strong from this angle, but we will finesse all these settings when we render in Chapter 11. For now, it's looking pretty good!

Figure 7.70. Set the repeat value for the fractal map.

Figure 7.71. The wheel looks pretty good!

Tire Summary

Congratulations! You have made your first somewhat complex shading network, as shown in Figure 7.72. By now you should have a pretty good idea of how to get around the Hypershade and create shading networks. To recap, we are using a ramp to place the two Tire and Rim shaders on the wheel, as well as using it to place the bump map on just the tire by using a reverse node. The more you make these shading networks, the easier they will become to create.

Figure 7.72. Your first complex shading network!

This type of shading is called procedural shading, because we used nothing but stock Maya texture nodes to accomplish what we needed for the wheels. In the following sections, we'll make good use of image mapping to create the decals for the wagon body as well as the wood for the railings.

You can load the file RedWagonTexture_v01.ma from the Scenes folder of the RedWagon project to check your work or skip to this point.

Figure 7.73. We need to add the body decals.

Figure 7.73 shows you the decals that need to go onto the body of the wagon. This includes the wagon's logo, which we'll replace with our own graphic design, and the white stripe that lines the side panels.

Instead of trying to make a procedural texture as we did with the wheel, we will create an image map that will texture the side panels' white stripe. The stripe is far too difficult to create otherwise. We will create an image file using Photoshop (or other such image editor) to make sure the white stripe (and later the Red Wagon logo) lines up correctly.

Mapping polygons can involve the task of defining UV coordinates for them so that you can more easily paint an image map for the mesh. When you create a NURBS surface, UV coordinates are inherent to the surface. At the origin (or the beginning) of the surface, the UV coordinate is (0,0). When the surface extends all the way to the left and all the way up, the UV coordinate is (1,1). When you paint an 800 × 600–pixel image in Photoshop, for example, it's safe to assume that the first pixel of the image (at X = 0 and Y = 0 in Photoshop) will map directly to the UV coordinate (0,0) on the NURBS surface, while the topmost right-corner pixel in the image will map to the UV (1,1) of the surface. To that end, mapping an image to a NURBS surface is fairly straightforward. The bottom of the image will map to the bottom of the surface, the top to the top, and so on. Figure 7.74 shows how an image is mapped onto a NURBS plane and a NURBS sphere.

The locations in the image, marked by text, correspond to the positions on the NURBS plane. The sphere, because it is a surface bent around spherically, shows that the origin of the UV coordinates is at the sphere's pole on the left and that the image wraps itself around it (bowing out in the middle) to meet at the seam along the front edge as shown.

Figure 7.74. An image file is mapped to a NURBS plane and a NURBS sphere. Notice the locations marked in the image and how they map to the locations on the surface, with the pixel coordinates directly corresponding to the surface's UV coordinates.

When you're creating polygons, however, this is not always the case. You sometimes will have to create your own UV coordinates on a polygonal surface to get a clean layout on which to paint in Photoshop. While poly UV mapping becomes fairly involved and complicated, it is a concept that is important to grasp early. When poly models are created, they do have UV coordinates; however, these coordinates may not be laid out in the best way for texture image manipulation.

Working with the A panels

Note

This section will assume you have some working knowledge of Adobe Photoshop. You can skip the creation of the maps and use the maps already on the CD, which are called out in the text later in the exercise.

First, let's take a look at how the UVs are laid out for the A panel that we modeled first in Chapter 6.

1. Using your scene or the scene file RedWagonTexture_v01.ma from the Scenes folder of the RedWagon project, select the A panel on one side of the wagon and choose Window → UV Texture Editor, as shown in Figure 7.75.

   The UV Texture window works almost like any other view panel. You may navigate the window and zoom in and out using the familiar Alt + mouse button combinations.

   

   Figure 7.75. The A Panel in the UV Texture Editor

2. RMB+click on any part of the wireframe layout in the UV Texture Editor window, and select UV to enter the UV selection. Select the entire wireframe mesh on the lower right, as shown in Figure 7.76. You'll notice that green points are selected—almost as if they were vertices. These are UV points and they are what define the UV coordinates on that part of the mesh. Look in the Perspective view panel and you will see the entire front face of the A panel is selected as well the green UV points (also in Figure 7.76).

   

   Figure 7.76. Select the UVs on this part of the A panel mesh.

   Feel free to select parts of the UV layout in the UV Texture Editor to see what corresponding points appear on the mesh itself in the persp panel. This will help orient you as to how the UV layout works on this mesh.

3. Now we are going to again lay out just this area of the mesh's UVs. Because we already have the entire front side of the panel selected in UVs, let's convert that selection to poly faces on the model. In the Polygons menu set and in the main Maya menu bar, choose Select → Convert Selection → To Faces. Now the front faces of the A panel mesh are selected, as shown in Figure 7.77. You can always manually select just the front faces of the mesh, but this conversion method is much faster. The UV Texture Editor shows just those faces now.

   

   Figure 7.77. Convert the UVs you just selected to a face selection. This method easily isolates the front face of the A panel for us to lay out their UVs again.

4. With those faces selected, make sure you are in the Polygons menu set. Choose Create UVs → Planar Mapping

   

5. Now the front face has a much simpler UV layout from which to paint. However, it is centered in the UV Texture Editor and will overlap the other UVs of the same mesh. We should move and size it to fit into its original corner, more or less, to make sure no UVs double up on each other. In the UV Texture Editor, right-click on the wireframe and select UV to enter UV selection. Select all the UVs on those faces and you will notice that all of the UVs for the A panel mesh appear in the UV Texture Editor, and you can see the overlap. See Figure 7.79.

   

   Figure 7.78. Create a Planar Projection for the UV layout.

   

   Figure 7.79. The UVs for the A panel, with the front side's UVs still selected

6. Press W for the Move tool, and move the selected UVs to the side of the UV Texture Editor. Press R for the Scale tool, and scale it down a bit to fit into the corner, as shown in Figure 7.80.

   

   Figure 7.80. Position these UVs to make sure they do not overlap the rest of the A panel mesh's UVs.

7. Earlier in the chapter, you saw how to write out a PSD file with a UV snapshot as one of its layers. We'll use a similar technique to paint the decal for the panel. Click on an empty area of the UV Texture Editor to deselect everything. Then, in Object Selection mode (press F8 if you need to exit Component Selection), select the A panel mesh in the persp panel.

8. In the UV Texture Editor window, select Polygons → UV Snapshot to open the Options window. Set both Size X and Size Y to 1024. Change the image format to TIFF, then click the Browse button at the top next to File name field, and navigate to the RedWagon project's Sourceimages folder on your hard drive. Name the file ApanelUV.tif and click Save. Leave the UV range set to Normal (0 to 1) and click OK. See Figure 7.81.

   

   Figure 7.81. Settings for the UV Snapshot

WORKING IN PHOTOSHOP

Next, we'll go into Photoshop to paint our map according to the UV layout we just output.

1. In your OS file browser, navigate to the RedWagon project's Sourceimages folder and open the file ApanelUV.tif in Photoshop. Figure 7.82 shows the layout of the UVs that we will use to create the white stripe for the front of the A panel.

2. In Photoshop, create a new layer on top of the background layer that is the UV layout (white on black as shown). Using the Bucket tool, fill that new layer with the same red we used on the shader in our scene. To do so, click the foreground color swatch in Photoshop and set the H to 355, S to 91 percent, and B to 65 percent, as shown in Figure 7.83. Click OK.

   

   Figure 7.82. Working with the UV layout for the A panel will be easy.

   

   Figure 7.83. In Photoshop's Color Picker, create the same red we used for the wagon.

3. Using the Bucket tool, click to fill the entire image with the red we just created. The trouble is that now we can't see the UV layout. Set the Opacity of the red layer in Photoshop to 50 percent, as shown Figure 7.84.

   

   Figure 7.84. Set the opacity for the red layer in Photoshop so we can see the UV layout on the layer below.

4. Set Photoshop's foreground color to white. Using the Line and Brush tools set to a width of about 6 pixels, draw a stripe following the UV layout lines, as shown in the image in Figure 7.85. This will place that white stripe along the A panel's outer edge because the UV lines we are following correspond to that area of the mesh. The rest will be left to be red.

   

   Figure 7.85. Follow the UV lines to draw the white stripe.

5. You may have drawn directly on the red layer in Photoshop or created a new layer for the stripe. In either case, set the Opacity of the red layer back to 100 percent so you can no longer see the UV layout. Your image file should look like the one in Figure 7.86. Save the image as ApanelStripe.tif in the Sourceimages folder of your RedWagon project. You may keep the layers in the TIFF file, or you may choose to flatten the image or merge the layers. It might be best to keep the stripe and red on separate layers so that you can go back into Photoshop and edit the stripe as needed.

   

   Figure 7.86. The striped image file

CREATING AND ASSIGNING THE SHADER

Now let's create the shader and get it assigned to the geometry.

1. Back in Maya, open the Hypershade and select the Red shader. Duplicate it by choosing Edit → Duplicate → Shading Network in the Hypershade window, as shown in Figure 7.87.

   

   Figure 7.87. Duplicate the original Red shader.

2. Name the new shader (called red1) ApanelStripe. Open the Attribute Editor and click on the Map button (

   
   

   Figure 7.88. Select the ApanelStripe.tif file.

3. In the Hypershade, you might see that the Shader icon has turned somewhat transparent. Maya is automatically mapping the Transparency attribute of the shader as well as the color. Double-click the shader to open its Attribute Editor, RMB+click on Transparency, and select Break Connection from the context window, as shown in Figure 7.89. This will set the shader to the same red we used earlier, but now it will give us a stripe along the side A panel.

4. Assign the ApanelStripe shader to the A panel mesh, and press 6 for Texture Display mode in the persp panel. See Figure 7.90. The stripe lines up well.

Note

You may skip the image creation in Photoshop and use the ApanelStripe.tif image file found in the Sourceimages folder of the RedWagon project on the CD.

Figure 7.89. Break the connection to the Transparency attribute.

Figure 7.90. The stripe!

COPYING UVS

Now we need to put the stripe on the other side's A panel. Select the other A panel and assign the ApanelStripe shader to it. You'll notice that no stripe appears. (See Figure 7.91.) This is because the UV layout for this A panel has not been set up yet. There's no need to worry; we don't have to redo everything we did for the first A panel. We can essentially copy the UVs from the first A panel mesh to this one.

1. Select the first A panel (with the stripe) and the second panel (without the stripe). In the Polygons menu, set choose Mesh → Transfer Attributes

   

2. Now the stripe appears on the inside of that back A panel, and not on the outside as we need. Select that A panel and choose Modify → Center Pivot.

   

   Figure 7.91. Assign the ApanelStripe shader to the other side's A panel.

   

   Figure 7.92. The Transfer Attributes settings

   

   Figure 7.93. The stripe is on the correct side now.

3. In the Channel box, enter a value of −1.0 for the Scale X, and the stripe will flip to the correct side, as shown in Figure 7.93.

4. With that A panel still selected, choose Modify → Freeze Transformations.

You can load the file RedWagonTexture_v02.ma from the Scenes folder of the RedWagon project to check your work or skip to this point.

Note

The file texture we'll use for the panels were painted in Photoshop to place the stripes and logo properly on the wagon using their UV layouts. Study the image file and see how it fits on the mesh of the wagon. Try adjusting the image file with your own art work to see how your image map affects the placement on the mesh.

Working with the B Panels

With the A panels done, we'll move on to the B panels, using much the same methodology we did with the A panels. To begin, follow these steps:

1. Select one of the B panels, shown in Figure 7.94, and open the UV Texture Editor window.

   

   Figure 7.94. Starting on the B panels

2. As we did with the front face of the A panel, select the UVs on the lower-right side of the layout in the UV Texture Editor, as shown in Figure 7.95, to isolate the front face of the B panel.

   

   Figure 7.95. Select the front face UVs for the B panel.

3. Choose Select → Convert Selection → To Faces. You have isolated the front face of the B panel.

4. Choose Create UVs → Planar Projection

   
   

   Figure 7.96. The planar projection creates a nice UV layout for the front faces of the B panel.

   

   Figure 7.97. Put the front face UVs on the side.

5. Convert the selection to UVs and use Move (W), Scale (R), and Rotate (E) to position the UV layout for that front face, as shown in Figure 7.97.

6. Press F8 and select the B panel mesh. In the UV Texture Editor, save a UV snapshot called BpanelUV.tif to the Sourceimages folder of the RedWagon project.

7. Open the BpanelUV.tif image in Photoshop, and follow the same steps as you did for the A panel to lay down a red layer and paint a stripe along the layout, as shown in Figure 7.98. It's best to save the stripe on its own layer in Photoshop because you will probably need to edit and reposition the stripe to make sure it lines up with the A panel stripe once you assign the shader.

   

   Figure 7.98. Create the B panel's stripe in Photoshop using the UV snapshot.

8. Create your own logo to place in the middle of panel B, and place it in the Photoshop image file, as shown in Figure 7.99. Save the image file as BpanelStripe.tif into the Sourceimages folder.

9. Duplicate another Red shader and, as you did previously, assign the BpanelStripe.tif as its color map. If needed, disconnect the transparency from the shader as you did with the A panel's shader. Name the shader BpanelStripe.

   

   Figure 7.99. Create the logo in Photoshop.

10. Assign the BpanelStripe shader to the B panel, as shown in Figure 7.100.

Note

You may skip the image creation in Photoshop and use the BpanelStripe.tif image file found in the Sourceimages folder of the RedWagon project on the CD.

Figure 7.100. The B panel has its decals!

CREATING THE OTHER B PANEL TEXTURE

Finally, we need to create the shader for the other side's B panel. Assign the BpanelStripe shader to the other B panel. Nothing will happen because the UVs for the second B panel are not set up yet.

Figure 7.101. Copying and flipping the UVs to the other B panel

However, because there is a logo with text, setting up its UVs will not be as simple as copying the UVs from the first B panel and then mirroring the mesh, as we did with the A panel with a Scale X of −1.0. Doing so will make the logo and text read backward. First, let's copy and flip the UVs to the other B panel.

1. Select the first B panel with the correct texture, and then select the other side's B panel and choose Mesh → Transfer Attributes

   

2. We have to go back to Photoshop and create a second BpanelStripe.tif image file with a mirrored logo. In Photoshop, create a marquee around the logo and mirror or flip the canvas horizontally. See Figure 7.102.

3. Select the logo portion of the image, and flip that vertically as shown in Figure 7.103. Save the image as BpanelStripe_2.tif.

   

   Figure 7.102. Flip the original image horizontally to fit the new UV layout of the second B panel.

   

   Figure 7.103. Flip the logo vertically and save the image as its own file.

4. Duplicate the BpanelStripe shader in the Hypershade by selecting the shader and choosing Edit → Duplicate → Shading Network. The copy is called BpanelStripe1.

   

   Figure 7.104. Assign the new image file to the new BplaneStripe1 shader.

5. Select the newly copied BpanelStripe1 shader and graph its input and output connections (

   

6. The stripe and logo are displaying on the wrong side of the B panel. Select the mesh and center its pivot.

7. Set the Scale X attribute for the B panel to −1.0 to mirror it. Now the stripe and logo decals will show up on the correct side of the panel. Select the mesh and freeze its transforms. Figure 7.105 shows the wagon so far.

Figure 7.105. The wagon has decals on both sides!

Right now the floor of the wagon is red, like the rest of its body. However, the real wagon has a blue floor, not red. If you select the mesh for the wagon's floor (named wagonFloor) and assign the Blue shader we created, the whole body of the wagon turns blue, and that is not what we need. We only need the inside and bottom of the floor to be blue and not the front and back sides of the wagon's body.

Figure 7.106. Select the floor faces.

We will make a face assignment instead of dealing with UVs and image files. RMB+click on the wagon floor mesh, and select Face from the marking menu. Select the two faces for the floor itself, as shown in Figure 7.106.

With the faces selected, assign the Blue shader from the Hypershade window and you're done! We have a blue floor. All that remains now are the screws, bolts, handle, and wood railings.

You can load the file RedWagonTexture_v03.ma from the Scenes folder of the RedWagon project to check your work or skip to this point.

We will go back to procedural shading, and use the Wood texture available in Maya to create the wood railings, as you did with the Axe exercise earlier in the chapter. Begin here:

The wood railings are finished! Now, for some extra challenge, you can use pictures of real wood to map onto the railings for a more detailed look. The procedural Wood texture can give you only so much realism. If you create your own wood maps, use your experience with the side panels to create UV layouts for the railings so you can paint realistic wood textures using Photoshop.

Now that the railings are done and you have test renders, the black front bullnose should look pretty smooth. The actual wagon's bullnose has a texture similar to the black tires.

Figure 7.113. Create a bump map.

Figure 7.114. Set the repeat values for the fractal bump map.

Figure 7.115. A nice bump for the bullnose

Now we'll create a simple Metal shader for the screws, bolts, and handlebar for the wagon, as we did for the Axe exercise earlier in the chapter.

Figure 7.116. Select all the metal screws, the bolts, and handlebar and assign the Metal shader to them.

Because metal is a tricky material to render, and a lot of metal's look is derived from reflections, we will finish setting the Metal shader's attributes in Chapter 11 when we render the wagon. We will enable raytracing to get realistic reflections and gauge how to best set up the Metal shader for a great look.

Figure 7.117 shows the wagon with all its parts assigned to shaders. Figure 7.118 shows a quick render of the wagon as it is now.

You can load the file RedWagonTexture_v04.ma from the Scenes folder of the RedWagon project to check your work or skip to this point.

Figure 7.117. The wagon in the Perspective panel

Figure 7.118. A current render of the wagon