All sculpting in Mudbox starts from a base mesh. A base mesh is a polygonal model made up of vertices that are connected to each other by edges to produce faces (Figure 3.1).

Figure 3.1. Vertices, edges, and faces make up this polygonal head model.

In the case of the egg created in Chapter 1, we used a Sphere primitive that we scaled to be our egg base mesh. Even though sculpting and painting your model is the core function and fun part of using Mudbox, having a problematic base mesh can bring that fun to an abrupt end and leave you extremely frustrated with an unusable sculpture you spent hours on. It is vital that you understand the requirements of a good base mesh and proper UV layout to get the results you want when you sculpt and paint your model.

Even if the original model did not start out as a polygonal model, its conversion to a polygonal model in either .obj or .fbx format is what you will start with in Mudbox. However detailed, this model and all its parts will be brought into Mudbox at subdivision level 0.

Triangles, Quads, N-gons, Poles, and Uniformly Spaced Geometry

As I mentioned, all models are made up of vertices, edges, and faces. The edges connect the vertices to form polygons. Even though Mudbox supports polygon faces with a maximum of 16 edges, your base mesh should ideally be composed entirely of four-edged polygons, which are also referred to as quads. The reason for this is that when you subdivide your model, polygons will be divided by 4, so if your model is a quad (that is, composed of four edges), then it will be divisible by 4 and will result in smaller quads inside each divided quad.

Figure 3.2 shows how Mudbox subdivides a tri (triangle), a quad, a pentagon, a hexagon, and an n-gon. All the resulting subdivision polygons produce quads on the inside. However, notice how uniform the subdivision is with the square quad shape and how the rest of the shapes produce a hub, or pole, in the middle. These poles produce a dense collection of polygons around the center of the pole, causing the surface to pinch and produce undesired visual artifacts when you sculpt, smooth, deform, and paint your model.

Figure 3.2. Subdivision of a triangle, a square quad, a pentagon, an octagon, and an n-gon

The number of edges coming out of a vertex is called the valency. If you generate poles that have a valency of more than 5, you should reposition those poles in inconspicuous locations where they will not be seen. This is even more critical when you are working on an organic model, such as a human being or creature, versus a hard-surface model, such as a car, robot, or spaceship, because hard-surface models usually are not intended to undergo deformation unless they are specifically intended to be deformable characters by design (for example, cartoony characters of cars, planes, or trains).

Another consideration is the size and distribution of your polygons. If you have long, thin polygons, they will get subdivided accordingly, creating artifacts when you sculpt. You want all your polygons evenly distributed in as close to a square shape as possible.

In Figure 3.3, planes A and B are both subdivided four times. Using the Sculpt tool on plane A produces jagged banding because each of the subdivisions is a smaller thin rectangle. In contrast, a subdivided plane B produces excellent results because you are subdividing squares with equal sides. The ratio of the width divided by the height of a rectangle is called the aspect ratio. A square has an aspect ratio of 1:1 because the height and width are the same, whereas the rectangles in plane A have an aspect ratio of 1:4. The only way we can get plane A to sculpt better is to subdivide it further, which wastes geometry and computing resources to get the same result we would have if we had used more uniformly spaced geometry.

Figure 3.3. Subdividing square quads versus rectangular quads

That said, it is impossible for all of your polygons to have an aspect ratio of 1:1. Getting some poles in your model is also unavoidable. Even if your model is entirely composed of quads, you will still have poles due to the topology of your edge loops. However, if you stick to the following three best practices, you will lessen your problems with subdividing, sculpting, and painting your model:

• Make sure your model is composed of quads. Occasional triangles or n-gons are acceptable only if you have a good place to hide them on the model, or if you have a hard-surface model that will not deform in the area where the triangles or n-gons are located.

• Make sure all the quads in your model have an aspect ratio as close to 1:1 as possible. If you find that you have skinny, long rectangles in your model, add some edge loops, to make the quad distribution more even. (Edge loops are explained in the following section.)

• Make sure the valency for all your poles is at 5 or less. If you absolutely need to have any poles that have a valency greater than 5, make sure they are tucked away somewhere not visible.

Problematic and Nonmanifold Geometry

Mudbox supports two-manifold polygon topologies. Polygon meshes that have two-manifold topology can be split along various edges to unfold and form a flat surface with no overlapping sections. Mudbox does not support nonmanifold topology. All 3D modeling applications can produce nonmanifold polygons either by accident or by a modeling operation such as deleting faces, extruding, or Boolean operations. Some 3D modeling applications provide tools such as Maya's Mesh → Cleanup feature (Figure 3.4) for checking and fixing this problem.

Figure 3.4. Maya's Mesh Cleanup dialog box

Every polygon has a face normal that determines which side of a polygon is the front and which side is the back. It is often represented by an imaginary line that is perpendicular to the surface of a polygon. Face normals are important because sometimes when you bring a model into Mudbox, certain parts of the model are not visible, and that is a good indication that the face normals are reversed. This situation can be detected and easily remedied in your 3D application just by reversing the face normals on the problematic faces.

Symptoms of problematic and nonmanifold geometry are as follows:

• Edges that do not connect to two faces, open seams, and overlapping edges in your model

• Polygons that are connected by only a vertex and no edges

• Vertices that are surrounded by more than one sequence of edges and faces

• Adjacent polygons with normals facing in opposite directions

• Floating or overlapping stray vertices in the model

• Lamina faces, which are faces that share all edges, mostly resulting from aborted extrude operations

If your base mesh is having problems loading or is displaying uncharacteristic anomalies when you load it, you likely have one of the preceding issues. To fix these problems, use cleanup features found in some 3D modeling applications, such as the Mesh → Cleanup feature in the Polygons menu set of Maya (Figure 3.4), read up on fixing these problems in polygonal modeling books, or seek the help of a polygonal modeling expert. Figure 3.5 shows some examples of nonmanifold geometry.

Figure 3.5. Three examples of nonmanifold geometry: T-shaped, bowtie, and flipped normal

Now that you have seen the importance of having a good base mesh to start with, you are ready to look at another important aspect of a base mesh, its UV layout.

Just as X and Y are coordinates of a point in 2D space, U and V are coordinates of points on the surface of a model. It is easy to identify a point in flat 2D space by its coordinates, but to do the same with a complex polygon mesh, you first need to unfold it into a flat surface—making sure there are no overlapping sections, so that every coordinate corresponds to a unique point on the surface of the mesh. This unwrapped 2D surface called a UV map stores the correlation between the pixel locations in the image and the vertices on the model. A good example to better understand UVs is a paper airplane (Figure 3.6).

Figure 3.6. A paper airplane with a United States Air Force decal on its wings

If we were to instruct a printer to print the United States Air Force insignia on a paper airplane, we would have to unfold the paper airplane (Figure 3.7) and indicate the coordinates of where the decals would go when the paper is completely flat (Figure 3.8).

UV coordinates are the positions of pixels on the surface of the 3D mesh. Those pixels can represent color, depth, and light orientation in the form of a texture, displacement, or normal map. The concept of unwrapping a 3D model is similar to the unwrapping of the paper airplane but is more involved because, unlike the paper airplane, complex 3D objects (such as a head, body, or spaceship) have many facets and we need to know where to cut seams to get the best flattened representation. You saw an example of an unwrapped UV map when you looked at the UV view of our egg in Chapter 1. All the mesh primitives in Mudbox, such as the Human Body (Figure 3.9), already have UV maps created for you. It would be a good idea to load all of them and take a look in the UV View at how the different models and shapes are unwrapped.

Figure 3.7. Unfolding the paper airplane

Figure 3.8. The unfolded paper airplane

Figure 3.9. UV map for the Human Body mesh in Mudbox

As mentioned, the two-manifold geometry that Mudbox supports, by definition, can be split along various edges to enable the shape to be laid out completely flat. There are different tools and methods available to you to create UV maps or UVs for your model. The process of creating UVs for a mesh is called UV mapping. Unfortunately, Mudbox does not contain any tools to create or modify UVs. Mudbox will, however, automatically subdivide the area within the UVs for you when you subdivide your model and choose to paint on it on a level greater than 0. Most major 3D applications, including Maya, have many UV mapping tools, such as automatic, planar, cylindrical, and spherical mapping.

There are applications that also create automatically generated UVs that are randomly arranged, and humanly unreadable, but these randomly laid out UVs do enable you to 3D paint without having to manually lay out UVs. Although this is a solution, it is not optimal because you will not be able to match any 2D patterns to the random layout of the flattened polygons. There are also tools and technologies being developed, such as Ptex developed by Walt Disney Animation Studios, that might eliminate the need for manually laying out UVs in the future. This will be a welcome solution for our vocation because it automates a stage in the process. However, this technology is still in development and will hopefully find its way to the most commonly used 3D tools in the near future. In the meantime, we still have to unwrap UVs by using existing tools and applications. The tool I prefer to use to lay out UVs is a brilliant application called UVLayout by Headus (www.uvlayout.com), which makes the process extremely fast and easy.

A tool such as Maya or UVLayout enables a user to cut the seams on the model to break it into multiple pieces called UV shells. Then these UV shells are flattened individually to have no intersecting lines or overlapping pieces. As these UV shells are flattened, take care to evenly space the polygons so they don't compress or stretch too much. As you can see in Figure 3.10, the UVs provided for the Human Body mesh have areas that are subject to stretching and compressing. UVLayout color codes the areas that will stretch in variations of red, and the areas that will compress in variations of blue.

Figure 3.10. This UV map displays areas that are subject to stretching and compressing by coloring them in shades of red and blue, respectively (see color insert).

Stretching and compressing causes an even texture such as a checkerboard to appear nonuniform on the surface of a model. Figure 3.11 demonstrates a checkered pattern applied to the Human Body mesh, and as you can see, there is some stretching of this pattern on the chest, right below the clavicular notch, which is the indentation at the base of the neck. You can also see compression of the checkered pattern in the neck and forehead area. These can be easily remedied with a bit more work in UVLayout to produce Figure 3.12.

Figure 3.11. The Human Body mesh with the default UVs provided in Mudbox displaying stretching and compression (see color insert)

Figure 3.12. The Human Body mesh with modified UVs in UVLayout displaying a more uniform checkered pattern (see color insert)

The other feature you will notice in both Figures 3.11 and 3.12 is that the checkered pattern does not continue through the seams. Texture painters who used to have to paint on UVs as 2D images had to come up with creative ways to match the patterns so the seams would not appear. Of course, painting in Mudbox eliminates the need to do that because you can directly paint on the seams, and the continuity of your brush strokes will be preserved through the seams. This is one of the most powerful and useful capabilities of Mudbox, and many texture artists use Mudbox for this reason alone.

After the seams are cut and the pieces are unwrapped, they will have to be arranged or packed to fit in the first square tile of UV space, making sure that as little space as possible is wasted. As you look at the UVs for the meshes provided in Mudbox, you will notice that they all are contained within one square UV tile, or quadrant, within the UV texture space. This square UV tile matches up directly to a square image that is created when you paint on the model. You can specify as much or as little detail as you want by the size of the image that corresponds to the square UV tile. If the object is going to be looked at closely, you would need to specify a 2K or 4K map size; if it is going to be viewed from afar, you don't need as detailed a map size. You may recall that we chose a 2K map size for our texture, displacement, and normal maps for the egg in Chapter 1 because we were going to look at it up close.

You can distribute UVs outside the first tile, which is also referred to as the 0 to 1 UV range, if the rendering application or game engine you will be outputting to supports this capability. This will enable you to place more-prominent or important parts of the model into their own UV tile region to paint greater detail on them. Then you will be able to paint multiple high-resolution maps and show much more texture detail on your models.

Another way you can save UV space is to fully overlap symmetrically opposite UV shells that will have symmetrical paint applied to them on top of each other, and use the space that is left for other parts of your model that require more detail.

The polygons with a clockwise winding order are displayed in blue, and the ones with a counterclockwise winding order are displayed in red. To change the winding order of a UV shell, you can use the Polygons → Flip function in Maya's UV Texture Editor.

This is better illustrated by looking at Figures 3.13 through 3.15.

Figure 3.13. UVs in default view

Figure 3.14. Good UVs with texture borders highlighted by clicking the Toggle the Display of Texture Borders for the Active Mesh button in the Maya UV Texture Editor

Please note that other 3D applications besides Maya that have their own UV creation and manipulation capabilities may have similar features for you to detect and correct these UV issues.

Figure 3.15. Bad UVs with texture borders highlighted by clicking the Toggle the Display of Texture Borders for the Active Mesh button in the Maya UV Texture Editor

Proper UV layout of your model is critical for Mudbox because you can paint on your model or export texture, displacement, and normal maps from your model only if your model has UVs that follow these guidelines:

Whether you are the only one working on your model or you have a model in a pipeline, a well-documented model will save you a lot of time. Most production houses have their own naming conventions that you will have to adhere to, but you can also come up with your own. This is an indispensible practice because it will help you find parts easily in a list.

It's a good idea to name everything while you are creating the parts of your model, or at short intervals of creating your model. Because your model will be used on multiple platforms that treat capitalization and special characters differently, it is also a good idea to use only lowercase characters and to use an underscore to indicate a space. Always identify the work with your name and indicate whether the part is on the left (lf), right (rt), center (cn), upper (up), or lower (lw) section of the model. Be as specific as you can with your naming—for example, for humans, use anatomical terms, and for mechanical objects, get schematics to specify the correct names of parts.

Some good examples are as follows:

For the first example, I used an abbreviation of my name, arak; the name of the model, bertie; the part, arm_actuator; the distinction of the upper actuator denoted by the word up; and lf denoting that this is the left one.

In Mudbox, you can double-click on the name of an object in the Object List to name it. If you are bringing an .obj model into Mudbox from Maya, and you have named all of your objects in Maya, select the Groups On option in the File → Export Selection Options (Figure 3.16) in Maya, as this will bring the names from Maya into Mudbox.

Figure 3.16. Export selection options, with the Groups option set to On

Selection sets are a good way to group or organize components of your model. For example, you might want to group the entire arm with all of its pieces into a selection set so you can hide or freeze it. To do this in Mudbox, select all the individual pieces by using the Objects selection tool on the model. Alternatively, you can multiple-select them by holding down the Ctrl key in Windows or the Command key on the Mac in the Object List and then choosing Create → Selection Set and giving your sets a name. You can also create selection sets with faces by using the Select Faces tool to select faces on your models, and saving your selection by choosing Create → Selection Set.

To create your selection sets in Maya, select all the geometry you are going to be working with and then choose Create → Sets → Quick Select Set. Make sure to export your .obj model from Maya with the Groups option set to On in the File → Export Selection Options (Figure 3.16) because that will transfer your quick select sets into Mudbox as selection sets.

If no units or scale have been specified for your model, it is always safe to go with a true-to-life scale. In Mudbox, you can specify millimeter, centimeter, meter, or inch as the unit of measurement in the Linear Units drop-down menu in the preferences dialog box. To access the preferences dialog box, choose Windows → Preference in Windows, or Mudbox → Preferences on the Mac. Linear Units are in the User Interface section of the preferences dialog box (Figure 3.17). The default in Mudbox, as it is in Maya, is Centimeters.

Figure 3.17. Mudbox preferences Linear Units setting

In Maya, because I have the gridlines set to a foot, and the subdivision lines set to an inch, when we import the Human Body mesh exported as an .obj or .fbx file into Mudbox, we see that it is about 6 feet tall, which is the approximate height of a male human being (Figure 3.18).

Figure 3.18. The Human Body mesh scale is approximately 6 feet tall.

However, as you can see when all of the meshes in Mudbox are brought into the same scene, their scales vary (Figure 3.19).

Before you import your model, position it in the center of the XYZ origin, so that you will be able to use the X, Y, or Z mirroring capabilities.

Whether the final presentation of your sculpture will be a 2D image, a 3D turntable, or an animation, you will be narrating something about your model, and unless your narration is about Leonardo da Vinci's Vitruvian Man or an action figure twist-tied in its packaging, the T-pose tends to be pretty boring to look at. Your model would be better presented telling a story, and that can be accomplished with a good pose along with its composition in a narrative environment.

If the model is to be animated, it will likely already have, or be destined to have, a rig in its development pipeline. A good rig, or skeleton with good controls and effective skinning, is the optimal way to pose a model. A rig is a skeletal system with joints that you rotate, and effectors that you move to pose your model. Skinning, or enveloping is determining the weight or influence the rig will have on the polygons of your model so that as you manipulate your skeleton, the intended parts of the model are translated or rotated.

It would be very easy to pose your model by using its rig and then output the resulting pose as an .obj or .fbx file and import it into Mudbox for sculpting. It is also very convenient because you can continually and easily modify or update your pose and export your model if needed.

If you are, however, not working in a pipeline where you will get an already rigged model, or have no rigging and skinning experience of your own, you will quickly discover that rigging and skinning is an in-depth expertise. If you don't have the help of a good rigger, and need to rig and skin a complex model, you will be out of your depth in a very short time.

Figure 3.19. The differences in scale among the default Mudbox meshes

If the final output of your digital sculpture is a turntable animation, a 3D print, or a 2D image, you likely don't need to spend the time or go through the expense of rigging your base mesh. You can use the posing tools in Mudbox 2011 for almost all cases with a few exceptions.

Mudbox 2011 is the first version of Mudbox to introduce posing tools. Even though you could have used the Grab tool in earlier versions of Mudbox to push, pull, and reposition geometry, it was never intended to be a posing tool. If you are posing an organic biped or quadruped, the new pose tools in Mudbox 2011 are quite effective and powerful. You can also use the new pose tools to bend, deform, move, or twist and shape models that are nonorganic. We will go into these tools in depth and pose a character in Chapter 7.

There are, however, some instances where the pose tools in Mudbox 2011 are not effective, and you will unfortunately need to use alternate posing tools to get the results you need. A perfect example is the model we will be using in this chapter, which is a mechanical robot with many parts.

I modeled Bertie, the robot model we will be using in the rest of this chapter, in Maya in a neutral T-pose and rigged it by adding joints and a skeleton. I then posed the rig in a stance inspired by one of Ashley Wood's paintings.

You will now load a mesh into Mudbox and sculpt some surface details. This mesh was modeled in Maya, rigged, posed, and then its UV maps were created in UVLayout. I have included the Maya project with the posed robot for you on the DVD in the Chapter 3ertie folder.

Note that the very intricate UV map (Figure 3.20) has a lot of parts and would be a nightmare to paint in Photoshop, but this has no bearing on us because we are working in Mudbox. This is one of the biggest benefits of painting a model in Mudbox. In a production environment, we would overlap some of the repeated parts in the UV map and also pack the parts closer together, but for the example in this book, what we have will work just fine.

Note that even though we have a lot of parts, the pattern and surface distribution of the UVs are even with no stretching (Figure 3.21).

Figure 3.20. UV map for Bertie done in Headus UVLayout

Figure 3.21. Pattern applied to Bertie model in Headus UVLayout

You will now add weathering and wear and tear to the model. Before you do this, you should envision the wear and tear a robot like Bertie would go through. Gather reference images online to use as examples for your work. You can search terms such as banged up cars from the seventies, junkyard metal, Soviet WWII-era tanks, and old water heaters in your favorite search engine or photo reference site to get images for examples.

Understanding Sculpt Tool Basics

You will use the various sculpt tools with some custom settings to create the dents, scratches, and rust effects. When sculpting, you are constantly adding and subtracting from the surface of your model. At different stages of your sculpting session, you will add and subtract at different depths. Initially, as you are blocking in the general shape of your model, you will add, subtract, and move big chunks of surface on your sculpture, and as you get more to the detail and refinement portion of your work, you will work with smaller increments and decrements of surface detail. Whether blocking in the general shape or refining the sculpture, I find it best to do it in incremental stages, which will be easy to recover from in case of undesired strokes. While sculpting, you will need to balance between the size, the strength, the falloff of your tool, and the pressure you apply on the stylus.

Before getting started on Bertie, you need to understand some important tool properties and shortcut keys:

Size The size of the active tool is displayed as a circle with a center as you move your cursor onto your model. The inside of this circle is the area on the model that the tool will affect based on the tool's properties. You can change the size of the tool by holding down the B key and clicking and dragging your mouse or stylus on the surface of the model; you get visual feedback of the size, which corresponds to the size of the circle. Even though the B key also corresponds to the brush size in Maya, I assign the size to the Z key. This enables me to keep one hand at the bottom-left corner of the keyboard while sculpting, because Shift, Alt, and Ctrl are keys I constantly use and Z is closer to them. You will learn about keyboard customization later in this book.

Strength The strength of a tool corresponds to how deep an impression the tool makes on the surface of the model. Selecting the Invert Function check box or holding down the Ctrl key makes a stroke that pulls out the surface instead of pushing it in. You can adjust the strength by using the M key. However, I assign strength to the X key because, again, it is next to the Shift, Alt, and Ctrl keys that I constantly use while sculpting, enabling me to keep one hand at the bottom-left corner of the keyboard.

Stamp The Stamp image property of a tool uses a grayscale image ranging from black to white as the tip of your tool and modifies the surface based on the variation of color between black and white.

Falloff The falloff is a curve that displays the change in strength of your stroke from the center of the circle to the edge.

Stamp Spacing This is the frequency, or continuity, of the stamp on your stroke. The higher the setting within the range of 0 to 100, the more visible the gaps will be in your stroke.

Steady Stroke and Steady Stroke Distance Turning Steady Stroke on enables you to make a smoother, more continuous stroke. A vector displays on the tool cursor as you drag your mouse or stylus on the surface of your model, and the stroke is not drawn until the mouse or stylus has moved a distance specified in the Distance field.

Remember Size Selecting this option preserves the size of your tool if you move to another tool and return. If this is set to Off, the brush will inherit whatever the size of the tool used before it.

Smooth Tool The Smooth tool will smooth out the surface of your sculpture by averaging the vertices. This is one of the most useful tools in Mudbox. In fact, it is so useful that you can activate it by holding down the Shift key while you are using other sculpt tools. If the Smooth tool is not used properly, it may undo a lot of detail work, so it is important to make sure you have it set correctly before you start every sculpting session. First, make sure you choose a very weak strength for it, such as 10 or 20. Second, modify the falloff to match Figure 3.32.

Figure 3.32. Smooth tool falloff curve

Sculpting Dents

You will now add dents on the surface of Bertie so you don't have the fresh-out-of-the-factory look (Figure 3.33).

Figure 3.33. Dented body

Continue from the prior section or load the bertie_stage_01d.mud file from the Chapter 3ertieMudbox folder on the DVD. You will add some surface imperfections by using the Flatten tool:

1. Select the Flatten tool. Use the default falloff and a Strength of 4, and vary the Size between 10 and 30 as you sculpt. Use the Flatten tool preferences in Figure 3.34.

   

   Figure 3.34. Flatten tool properties

2. Sculpt the dents on the surface of your model by using small strokes. Press the L key and click and drag your stylus or mouse to move the light to see the variations on the surface and get a better view of your work.

3. Hold down the Shift key and click and drag your stylus or mouse to smooth out any areas that seem too severe.

4. Remember to sculpt the dents only on the dents sculpting layer by first clicking or tapping on the part and then selecting its dent layer in the Sculpt Layers tray. This is extremely useful because you might need to undo these dents as a whole, or dial up the opacity of your sculpt to go between a more dented or less dented version of your robot. Add dents to all three body parts, the arms, and the legs. Remember that only some of the parts have sculpt layers, and use more care when you are sculpting parts that don't have layers. If you change any parts that don't have sculpt layers, you will not be able to dial back their opacity.

5. Always look at your reference material for how the dents manifest themselves on the surface of metal vehicles or objects.

6. After you are finished sculpting, dial the opacity on the various layers of the parts to get to a weathered look you like.

7. Save your work as bertie_stage_02.mud after you are finished with each part. It is vital that you always save your work at intervals where you are happy with it. You can set an option to remind you to save at intervals you specify, by choosing Windows → Preferences in Windows (or Mudbox → Preferences on the Mac) and selecting the Save Reminder setting in the Status Line rollout (Figure 3.35). The reminder appears in the status line as a blinking red Save Text.

Figure 3.35. Save reminder and interval setting in the preferences

Sculpting Scratches

In this section, you will do the same thing you did when sculpting the dents, but now you will use different tools than the Flatten tool and will sculpt on a layer called scratches Figure 3.36). Continue from the prior section or load the bertie_stage_02.mud file from the Chapter 3ertieMudbox folder on the DVD.

1. Click the Sculpt tool and use the properties in Figure 3.37. Create the falloff in the Falloff properties by clicking on the two middle curve points and dragging them to the bottom-left corner. This creates a very sharp point for your tool.

2. Using different tool Size and Strength settings, make some scratches on the surface of your model, making sure you are working on the model's scratches sculpt layer that we created. You can also enhance some of the surface details, such as the front panel, by adding more detail in the form of protrusions and indentations around the edge.

3. Select the Steady Stroke property to make linear scratches. Experiment with changing the Steady Stroke Distance.

4. Test out the Sculpt tool with different Strength and Size settings.

5. When you are finished, use the opacity dials to adjust the opacity of your scratches sculpt layers to a level that looks good to you.

6. Save your work as bertie_stage_03.mud after you are finished with each part.

Figure 3.36. Scratches

Sculpting Rust

Again, you will do the same things as in the two previous sections, but now you will sculpt some rust in areas where you feel Bertie would get corroded from water, engine liquid leaks, and general weather. You will mostly use the Spray tool with a stamp to achieve this look. The resulting sculpt will have some more weathering in the form of corroded edges and streaks (Figure 3.38). Continue from the prior section or load the bertie_stage_03.mud file from the Chapter 3ertieMudbox folder on the DVD.

Figure 3.37. Sculpt tool preferences

1. Turn on Ambient Occlusion by clicking the eye icon next to it in the Viewport Filters tray. Click on the Ambient Occlusion viewport filter so that the properties show up in the Properties tray and make sure they match Figure 3.39. This will darken corners and indentations on the model to make the sculpting detail stand out. In 3D applications, Ambient Occlusion is a render layer that is created after the model is finished. In Mudbox, you can turn it on and off and work in real time with it on. This again is a powerful capability because it gives you a good idea of how your final Ambient Occlusion layer will look, and also you can sculpt and see the depth and corners darkened to add more realism to your model.

2. Adding rust is very similar to what you did with the egg in Chapter 1. You will be using the Spray tool from the Sculpt Layers tray, with the preferences and stamp shown in Figure 3.40.

   

   Figure 3.38. Corrosion and rust

3. Using different tool Size and Strength settings, sculpt some rust streaks and corrosion in areas of your model where water or a constant flow of corrosive fluids would create rusty texture. Remember to do your rust sculpting in the model's rust sculpt layer. Look at reference material on rusty metal to see the properties of a rusty surface, and replicate this on your model as best as you can. The Ambient Occlusion viewport filter gives you direct feedback on how the rusty areas will look.

   

   Figure 3.39. Ambient Occlusion preferences

4. When you are finished, use the opacity dials to adjust the opacity of your rust layer to a level that looks good to you.

5. Save your work as bertie_stage_04.mud after you are finished.

Sculpting Pouches

The last things to sculpt are the pouches. This is a departure from what you have been doing so far because you are not going to add detail to anything. Instead, you are going to sculpt an organic shape of ammo pouches from a blocky base mesh (Figure 3.41). To do this, you will hide the rest of the model and sculpt the pouches one by one.

Figure 3.40. Spray tool properties

The pouches have limited geometry, so you won't be able to add a lot of high-frequency detail. However, you will be able to provide a general shape of what a pouch looks like. When we are looking at the entire robot as a whole, the relative scale of the pouches is small, and any high-frequency detail would not be visible.

In this section, you will use the Grab, Bulge, Sculpt, Repeat, and Flatten sculpt tools. You can follow along with the Chapter3-sculpting_pouch.mov video in the Chapter 3videos folder on the DVD. Here are the steps:

1. Using the Objects selection tool, select any pouch you want to start with.

2. Choose Display → Hide Unselected to hide all the parts except the pouch you selected.

   The first tool you will use is the Grab tool, which moves the surface you click in the direction you drag the mouse or stylus. It is best to use it on lower subdivision levels to block the general shape of your sculpture. The Grab tool has a Direction property in the Advanced section of the properties that will constrain the movement of the tool to the direction of the Screen (which is the default), XY, YZ, or XZ planes, or Averaged Normal (the average of the normals of the surface). The Orient to Surface option in the Grab tool properties is extremely useful.

   

   Figure 3.41. Sculpted pouches

3. Press Pg Dn until you are on subdivision level 3. Use the Grab tool to change the shape of the pouch to one that looks more realistic. Adjust the Size and Strength properties of the tool as needed by pressing the Shift+B and Shift+M keys; this may require a little bit of experimentation. Drag the edges of the top and bottom corners of the pouch to match Figure 3.42.

4. Press Pg Up to get back to level 5. Use the Bulge tool with a Size of 10 and a Strength of 2 to bulge out the bottom of the bag to accommodate for content that would be weighing it down and creating folds on the surface. Change the Size to 4, and press Ctrl to reverse the bulge to go inward in the top and bottom center of the pouch (Figure 3.43). Place the brush where the clasp or button would go, and click and drag your mouse or stylus in a small circular motion. If the bulge is too rounded, you can use the Flatten tool to flatten it out.

5. Use the Sculpt tool to create some indented seam folds at the bottom two corners of the pouch and a line for the buttonhole (Figure 3.44). Remember to use Shift to smooth out any severe strokes.

6. 

   Use the Bulge, Grab, Smooth, and Sculpt tools to further refine your pouch shape. Remember that you don't need to add too much detail, just enough to make the shape stand out when you are looking at the entire robot.

7. Repeat these operations on the rest of the pouches, because it will be good exercise for you with the various tools and their properties.

8. Save your work as bertie_stage_05.mud after you are finished.

There is a saved version of bertie_stage_05.mud on the DVD for you to load and examine.

Figure 3.42. Blocking in the general shape

Figure 3.43. Use the Bulge tool to bulge out the pouch to accommodate for the weight of its contents.

Figure 3.44. Use the Sculpt tool to create seam folds and a buttonhole on top of the button.

Figure 3.45. Use the Repeat tool on the pouch flap to create edging.

In this chapter, you have gone through the requirements of a good base mesh:

You learned about the definition of UVs and the importance of a good UV layout when you need to export maps from Mudbox:

You went through the importance of a good naming convention and exporting your .obj files with the Groups option set to On. You learned the importance of posing and scaling your base mesh before you bring it in to Mudbox. Finally, you added sculpting details to the body of Bertie the robot and did your first sculpt in the form of a pouch.

You will be going through another more detailed sculpting session in Chapter 5, but hopefully by now you have a very good idea of how some of the main tools work and how their preferences can affect the surface of your model. Next you will paint Bertie.