There are two differing approaches to using a base mesh for digital sculpting.

The first is to start sculpting and to re-topologize at a later point in time. The benefit of this approach is that you have no barrier to your creativity at the onset of the project. You can start with a primitive or a very simple base mesh, and take your sculpture in any direction you desire without any extensive planning or modeling from the onset. However, you might run into a situation where you need more geometry, in which case you would need to interrupt your creative process to re-topologize and then continue sculpting.

The second approach is to give your final sculpture some thought and planning before you begin, and either model or obtain a base mesh that will accommodate the geometry you need for your final result. The benefit of this approach is that you will not have any interruptions during the creative process of sculpting and you could very well take your model to completion without having to re-topologize.

Neither of these approaches is perfect, because sometimes you might start out by sculpting from a primitive and never need to re-topologize, and sometimes you might plan your base mesh ad nauseam and still end up needing to re-topologize. Thus, it is a good idea to know about both approaches and decide which direction to take based on your project.

I presently favor the second approach in my workflow, and start by planning a good base mesh at the outset. However, I know and greatly admire many amazing digital artists who use the first approach of starting with a primitive.

I find that I have better results and a smoother workflow when I start with a base mesh that fits the guidelines discussed in Chapter 3, "Detail-Sculpting an Imported Model," where the geometry is as follows:

And with UVs, that have these features:

The two most used and universally common properties of every sculpt tool in Mudbox are its Size and Strength properties. The Size property represents how large of an area the tool will impact, and the Strength property represents how deep the tool will push in or pull out the surface. You can manipulate these properties in one of two ways: you can type a value in its field or you can use the B and M keys and click (or tap with a tablet) and drag visual cues on the surface of the model. The Size property is represented by a circle, and the Strength property by a line perpendicular to this circle at the center.

The third-most-used property of a sculpt tool is Invert Function. Every sculpt tool except the Grab tool has this property. The Invert Function property is extremely useful because it inverts the effect the tool has on the surface. For example, if Invert Function is selected, the sculpt tool will depress into the surface of the model (instead of pulling out the surface, as it does when Invert Function is not selected). The check box for this property is useful only if the majority of your strokes are in the reverse orientation of the tool. The best way to get the same effect as Invert Function is to hold down the Ctrl key.

Even though each and every sculpting tool has many properties, there are only a few that you will be constantly manipulating in your workflow while sculpting. These are as follows:

While sculpting, you can move your cursor back and forth between the model in the 3D view and the Properties tray on the right, but it is infinitely faster for your workflow if you use hot keys for the preceding functions, so you can keep working on your model without having to move back and forth. The following "Expert Tip" indicates are the settings I use; you can use the same ones or come up with your own based on your workflow.

EXPERT TIP

Because you use the Alt key to move the camera around your sculpture, the Ctrl key to invert the function of the brush, and the Shift key to activate the Smooth tool, your hand is constantly pressing and releasing keys in one of the two bottom corners of the keyboard, depending on whether you are right- or left-handed. It's a good idea to place other commonly used functions in this area as well.

For example, because I am right-handed and use the stylus or mouse with my right hand, I use the bottom-left corner of the keyboard to press Alt and Ctrl, I assign the Size function to the Z key (instead of B), and the Strength function to X (instead of M) because it helps my workflow tremendously. I also assign these five keys to the function buttons on the Wacom tablet so that if I am sitting back, and my hand can't reach the keyboard, I can use just the tablet's function keys to perform these functions. The other benefit to keeping your hand in the vicinity of these keys is that you also have very close and easy access to Undo and Redo, which are Ctrl+Z and Shift+Z.

The way to customize keyboard shortcuts is to click Windows → Hotkeys (Window → Hotkeys on the Mac) and find the function in the list of functions in the dialog box, and then type in your desired value. For example, find Change Brush Size and set the key to Z (case does not matter) and LMB (left mouse button), and then find Change Brush Strength and set the key to X and LMB.

Place other tools or options that you use frequently in the same vicinity by using the A, S, D, C, Q, and W keys.

Also note that the tools in the Sculpt Tools tray are mapped to the number keys in the same order as they appear in the initial default setting of the application. So the number 1 on your keyboard corresponds to the Sculpt tool, 2 to the Smooth tool, 3 to the Grab tool, and so forth.

The next important sculpting property is Falloff. The Falloff property is available for all the sculpting tools. Falloff represents a curve that indicates the strength of the tool from its center to its outer edge (Figure 5.4). The leftmost corner of the falloff curve represents the center of the tool, and the rightmost corner represents the edge, so the falloff curve itself represents only half of the tool and is mirrored to the left to encompass the entire brush. The top-to-bottom portion of the falloff curve represents the Strength of the tool.

Figure 5.4. The falloff curve

The shape of the falloff curve can be adjusted by moving the four curve points. The two curve points on each end can be moved only up and down because they represent the center and the edge of the tool. The two center curve points can be moved anywhere in the falloff curve graph area.

You can make the falloff curve into a straight line for a planar drop-off by aligning the curve points accordingly. Figure 5.5 shows you an example of the default falloff curves in the Falloff tray and their results on a plane. Incidentally, a plane is a great primitive to try out the various sculpting tools with their settings to get a good idea of their function.

As you make your own falloff curves, you can save them to the tray for future use by clicking the Store To button underneath the falloff curve in the tool Properties tray. The Snap check box allows you to snap the curve points on the grid. Figure 5.6 shows some user-created falloff curves and their result on a plane.

Figure 5.5. The default falloff curves on a plane

Figure 5.6. User-created falloff curves

A falloff curve that I use a lot, but that is not part of the default set, is a falloff curve with both middle curve points snapped to the leftmost corner, or center of the brush (Figure 5.7). I use this falloff in addition to the Sculpt tool to create sharp edges instead of using the Pinch tool.

To create this falloff curve, do the following:

Figure 5.7. Sharp-edge falloff brush]

Besides the Undo function, the other big advantage to digital sculpting is mirroring, or symmetrical sculpting. Using mirroring while sculpting enables you to sculpt one side of your sculpture and have the exact same strokes and shapes mirrored on the other side. Mudbox has some very powerful mirroring capabilities in its sculpting tools.

There are two ways to sculpt when using mirroring, or symmetry. The first is to turn mirroring on and sculpt, in which case the strokes you do on one side are duplicated on the other. The other way is to sculpt one side and then mirror your sculpture after the fact.

The Mirror property, another property that all sculpting tools have, is a drop-down menu that lists the various mirroring options. The first three mirroring options will mirror your work along the world axes. The next three options enable you to mirror along the model's local axes, treating the pivot point, or center of the object, as the center of mirroring.

The last and most unconventionally powerful mirroring option is the Tangent option. This enables you to mirror a topologically symmetrical object along a topological axis that you set up. Topologically symmetrical models have an equal number of faces on each half of the model, even though those faces are in different locations. There is usually a dividing edge loop that divides the model in half.

To work with the mirroring capabilities in Mudbox go through the following steps:

Figure 5.11. Tangent mirror sculpt

Symmetry is a huge time-saver and makes our lives a lot easier while sculpting symmetrical subjects. However, at times when you are sculpting, you might forget to turn on symmetry, which could be very frustrating. There are a couple of ways to overcome this.

One solution is to generate a 32-bit displacement map and use a 2D image-manipulation tool that can handle 32-bit images to copy, flip, and paste the sculpture from one side to another.

However, there is a way to do this in Mudbox that is a lot easier. For example, say we sculpted the ear on one side of the head and inadvertently turned off tangent symmetry in our model before we started sculpting the ear. There is a way to mirror the ear to the other side after the fact. This works with all mirroring, and luckily also with topological tangent symmetry as well. We will go through this example with the model we have been working on, where we sculpted the ear on one side and need to transfer it over to the other side (Figure 5.12).

The Use Stamp Image property enables you to use stamp images in combination with the sculpting and paint tools to sculpt or paint with the stamp image as the tip of your tool. This is mostlyuseful to create interesting repeating detail on the surface of your model. For stamps to be effective, you need to make sure that your model is subdivided appropriately to show the granularity level of the stamp on the surface of the geometry.

While sculpting, the stamp image's opacity values are used to mask which parts of the image get modified versus which parts do not. Black values on the stamp image produce absolutely no modification, while white values produce the most; the values in between have changes applied to the geometry based on their value.

To use stamps to sculpt, select the Use Stamp Image check box in the tool's Properties tray. Stamps can be applied with certain levels of uniformity, or randomness, based on the settings of the Use Stamp Image properties.

The stamp image can be flipped and rotated by using the Flip and Rotate buttons on top of the stamp image in the Use Stamp Image properties.

An important capability of using stamps to sculpt is using the Orient to Stroke function. This can be toggled on or off by clicking the Orient to Stroke button above the stamp thumbnail in the Use Stamp Image properties. This will allow the orientation of the stamp to follow the orientation of your stroke (Figure 5.16), like tire tracks orient themselves to the direction of a car.

The Randomize option lets you apply randomization based on the sliders to add rotational, horizontal, vertical, scale, and opacity jitter to your stroke with the stamp applied. In Figure 5.17, notice how we get a completely random-looking corroded effect by just using the Sculpt tool with one stamp, and turning on the randomize effects of the Use Stamp Image properties.

Figure 5.16. Orient to Stroke

Figure 5.17. Randomize application of the stamp

The Stamp Spacing property sets the rate at which the stamp image repeats on a stroke. It works whether or not the Use Stamp Image check box is selected. You should manipulate this property only if you want more gaps in your stroke or, more realistically, if you wantnone or fewer.

Steady Stroke is available for all sculpting tools except Imprint. It enables you to sculpt a more even or straighter stroke. This is done by displaying a vector when you begin your stroke. When your stroke has moved the distance specified in the Distance text box of the Steady Stroke property, the stroke is then applied to the model.

Steady Stroke is extremely useful when you want to sculpt lines or patterns that portray a smooth continuity in direction. If you want to sculpt in an actual straight line, or a shape that is more controlled and rigid, you can use the Curves option.

If you work with 2D illustration applications such as Adobe Illustrator, or NURBs in Maya, you are familiar with how useful curves are. In Mudbox, you can use built-in curves and modify them, or you can draw your own curves as guides to sculpt.

The curve tools are found in two places. To create a curve, choose Create → Curves and choose from a Circle, French Curve, Straight Line, or Square. Even though you might not think of straight lines or squares as curves, the reason they are called such is because they are constructed as curves. You can also create a curve by choosing Curves → New Curve and clicking to draw the curve points in the 3D view; use Undo (Ctrl Z) to undo the last point, and press Enter to end the curve creation process. If you want to close your curve, choose Curves → Close Curve.

You can edit the curve by selecting it in the Object List and moving the curve points.

To manipulate a curve, press C on the keyboard and use the left, middle, and right mouse or stylus buttons to rotate, translate, and scale the curve, respectively.

To duplicate a curve, choose Curves → Duplicate Curve.

To snap your tool to the curve to sculpt along it, select the curve in the Object List and press Enter, and then move the cursor to the curve. As it gets close to it, the cursor will snap to the curve.

You can sculpt repeating stamp patterns along the curve by choosing Curves → Stroke on Curve and filling in the dialog box with the number of stamps you want on the curve (Figure 5.18). This is very useful if you are going to have a repeating pattern along a curve or line, such as rivets, nails, sewing stitches, staples, and so forth.

Figure 5.18. Stroke on Curve dialog box

Buildup, which is available for the Sculpt, Smooth, Pinch, Flatten, Foamy, Spray, Repeat, Wax, Scrape, Fill, Knife, Smear, Bulge, Amplify, Freeze, and Mask tools, indicates the rate at whichthe tool will reach the Strength value.

For example, if you have a Strength of 100 and a Buildup of 50, you will get to the full Strength value with a very short stroke, whereas if your Buildup value is 10, it will take you longer.

Experiment with strokes on a plane that is subdivided five or six times with the Sculpt toolStrength set at 100 and Buildup at 10, 20, 40, 60, 80, and 100 to see the effects. The default Buildup for the Sculpt tool is 40, just in case you need to set it back to its default value. It's always a good idea to note the default value of a property because it is the value that the developers have deemed as a default average.

Flood, which is available to only the Sculpt, Smooth, Pinch, Flatten, Freeze, Foamy, Spray, Repeat, Wax, Scrape, Fill, Knife, Smear, Bulge, Amplify Mask, and Erase tools, applies the function of these tools uniformly on the entire surface of your model in one click of the Flood button. It's a great way to add uniform thickness and smoothness to the entire model. Note that Flood does not apply the function of the tools to surface areas that are hidden, frozen, or affected by a stencil.

Update Plane is a property of the Flatten, Wax, Scrape, Fill, and Amplify tools, located in the Advanced section of the tool Properties tray. When Update Plane is not selected at the onset of a stroke, a plane is determined based on the stamp's tangency to the contact point, and all the points on the surface are pulled in the direction of that plane for the duration of the stroke. For example, if you start the stroke on a sphere and move to its edge, you will create a plane tangent to the sphere from the point you clicked on it (Figure 5.19).

Figure 5.19. Wax tool with Update Plane off

However, with the setting selected, the plane toward which the surface is pulled gets redetermined and updated for each stamp update in a tool stroke (Figure 5.20). Having Update Plane selected is the desired setting while sculpting with the preceding tools, because the brush adheres to the curvature of the sculpted surface instead of the plane of the stroke's initial contact.

Figure 5.20. Wax tool with Update Plane on

Whole Stroke is also a property of the Flatten, Wax, Scrape, Fill, and Amplify tools and is located in the Advanced section. It causes the plane toward which the surface is pulled to be recalculated and updated for each vertex affected by the current tool stroke, as opposed to each stampupdate with the Update Plane function. The result is a slight variation of the Update Plane property, where a more planar effect continues throughout the stroke.

Before we get deeper into the tools, I want to mention that using and developing a large number of sculpting tools is not critical, just as it is not critical when you are doing traditional sculpting. Based on what you are trying to sculpt, you will determine a few tools that work best for you and continue to use those to get the shapes you want. You can customize the settings of a tool and save your custom variant if you discover you are repeating tool customization tasks. Save your custom tool by clicking on the tray's window drop-down menu and then clicking Add Tool.

The Sculpt and Wax tools are the workhorses of Mudbox, especially with the enhancements introduced in Mudbox 2010. In this version, the Update Plane option has been added to the Wax tool, giving it properties similar to adding clay to a traditional sculpture. The Wax tool is best used with the square stamp, to give the illusion of adding strips of clay to your sculpture.

The Flatten tool is another one of the most useful tools in Mudbox. You can use it to define planes while sculpting and to create flat surfaces.

The Foamy tool is a variation of the Sculpt tool with a softer result.

With all the properties and stamps you can apply to these tools, many new implementations remain to be discovered. I will cover a few that I use when we sculpt the model in the next chapter.

The Pinch tool is useful for creating creased corners. However, use it with caution because as it compresses and stretches geometry to create the effect, it creates undesirable topological effects.

Notice the nice crease created on the edge of a car by using the Pinch tool with Steady Stroke on (Figure 5.21). Although this looks like a nice hard edge, upon further examination, we notice that polygons are crammed in together to produce this crease, while adjacent polygons to those pinched to form the crease are stretched out (Figure 5.22).

Figure 5.21. Pinch tool with Steady Stroke on to create nice pinch on the edge of a car

Figure 5.22. Surface geometry compression and stretching caused as a result of the Pinch tool

The Smear tool has a similar property of moving vertices on the model's surface. The Smear tool could also cause undesirable effects when texturing or sculpting.

The Spray, Repeat, and Imprint tools enable you to place stamps on the surface of your model. You should be familiar with the Spray and Imprint tool because you have used them in previous chapters. The Repeat tool enables you to repeat a stamp along your stroke. This tool is extremely useful for creating repeated patterns such as stitching, rivets, screws, or nails on a path.

Even though you can lock sculpting on an object in the Object List, the Freeze tool enables you to freeze, or lock, certain vertices of the geometry so you cannot modify or sculpt them. The frozen faces get painted blue at varying opacities to indicate the amount of freezing. A fully opaque blue locks completely, while partially opaque blue allows the vertices to move slightly when a sculpting tool is applied.

To paint areas you want frozen, click and paint on the model. The painting takes into consideration all your tool settings such as Size, Strength, Falloff, Buildup, and Steady Stroke. In addition, you can erase the frozen area while holding down Ctrl, and smooth the edges of your frozen area by holding down Shift. Note that to smooth the areas of the edges of a frozen area, you need to have the Smooth & Paint Values check box selected in the Advanced section of the Freeze tool properties tray.

You can freeze your entire selected model by choosing Edit → Freeze Selected. You can invert the frozen areas by choosing Edit → Invert Freeze. To clear all frozen items, choose Edit → Unfreeze All.

If you are familiar with ZBrush, Freeze is analogous to Mask in ZBrush. If you are a user of both applications, note that what is referred to as the Mask function does something completely different in each application.

Both the Erase and Mask tools are used to erase or remove sculpting from layers. Neither one of the two tools works on the base mesh of a model; you have to have at least one sculpting layer to use them.

The Erase tool erases the sculpting on the layer to reveal the original base mesh, or other layers beneath it. Once something is erased, the only way to bring it back is through Undo. If the model is saved and loaded, there is no way to bring back what was erased.

The Erase tool erases sculpting on the current selected layer only. Nothing changes on the other layers or the original base mesh.

The Mask tool does the same thing as the Erase tool, but with a couple of big differences:

To clear the mask completely, turn on Invert Function in the Mask tool properties window, and click Flood.

To understand the function of these tools better, you will go through an exercise of using the Mask, Erase, and Freeze tools to add a wetsuit to the Human Body starter mesh. Follow these steps:

As you can see masking, freezing, erasing, and sculpting layers are extremely useful for creating models that can be modified on a layer-by-layer basis.

Figure 5.26. Erase the face area on the hood.