The 3D view is where all the creative magic happens. When you first see the 3D view, it consists of a gradient background and a grid. Imagine the rectangle where the 3D view is located as a viewfinder of a camera that you are looking through. There are many other standard and customizable viewports, but the one you start with is called the Perspective camera.

You will go through changing the camera to standard orthogonal or custom cameras in later chapters, but whatever your camera choice, you are able to see only one camera's contents in the 3D view. This is different from other 3D applications, because most of them usually have three or four camera views when you first start up.

There are some other things that pop up in the 3D view as you start working on your model. After you start dividing your model or stepping through its subdivision levels, you will see the subdivision level as well as the number of polygons in your model in a window at the top-right corner of the 3D view (Figure 2.5).

Figure 2.5. 3D view

You will also get a status indicator at the center right of the 3D view, telling you which mirroring method is activated Figure 2.5). You will learn more about how to use mirroring to sculpt and paint symmetrically in Chapters 5 and 7.

You will also occasionally get tool help that shows up in the left part of the 3D view. You can turn off the informative messages if you wish; you can do so in the User Interface Section of the Windows → Preferences (Mudbox → Preferences on the Mac) dialog box.

You can turn off the gradient background by deselecting the Gradient Background option in the Display menu.

You also have context-sensitive menus that you can activate in the 3D view by right-clicking on either the canvas or an object in the canvas. When you right-click on the canvas, you get a subset of the Display menu. When you right-click on an object, you get a menu that enables you to assign a new or existing material to the object, edit the material that is assigned to it, and rename or delete it or find out about its properties.

The UV view is where you see your active model's UV texture coordinates in addition to the active paint layer (Figure 2.6).

Figure 2.6. The UV view

Figure 2.7. UV view with multiple quadrants

This view enables to you to see UVs in the first quadrant (or tile region) in addition to ones that are laid out in multiple tiles (Figure 2.7). Here you will also see your different maps and layers applied to your UVs.

Note that all of your UVs should be laid out before your model gets into Mudbox. This view is just for viewing the UVs and textures applied to them and not for creating, interacting with, or changing the UVs.

The Image Browser is a viewer that helps you view your 2D image library. You can visually select images to be stamps, stencils, image planes, or high dynamic range (HDR) image-based lighting (IBL). Think of it as a sophisticated version of a File Open dialog box for 2D images.

The Image Browser is divided into three parts: the toolbar, or ribbon, on top; the thumbnails on the left; and the 2D view in the center (Figure 2.8).

The ribbon, or toolbar, is where you sort through your images, get information about them, and assign them to the various roles such as image plane backdrops, a stamp to sculpt with, or a stencil to paint on your model (Figure 2.9).

To point the Image Browser at an image folder, do one of the following:

Figure 2.8. Image Browser

Figure 2.9. Image Browser toolbar

Pick a folder from the list in the Bookmarks drop-down list. Within this drop-down list is also where you set your favorite image folders as bookmarks to save time navigating to them in future working sessions, or to quickly jump from one bookmark to another without having to navigate your hard drive to get to them. Setting bookmarks for your texture, stamp, stencil, and current working directories will save you a lot of time during a working session. After you select a folder or directory, the images in that directory will show up in the thumbnails strip to the left of the Image Browser. You can enlarge this strip to see more thumbnails by dragging the separator between the thumbnail strip and the 2D view.

You can show and hide the thumbnails by clicking the Show/Hide Thumbnail View arrow icon to the left of the file name text box. You can cycle through the images sequentially by pressing the spacebar.

After you have selected an image, the information section of the toolbar Figure 2.9) displays the image's name, dimensions in pixels, number of color channels, bit depth (8, 16, 32), and file size. Next to the image information you will see an information area that changes values as you move the mouse over your image. This section shows information about the image under the pointer, such as the X and Y position, the Red, Green, Blue, and Alpha (RGBA) values, and whether you have a high dynamic range (HDR) image, and its exposure value.

When you are viewing an HDR image, you can use the + and − keys to go up or down, respectively, in exposure value. These values are also called stops, based on the photography term f-stop, used to measure exposure. I cover HDR imagery and the significance of HDR photography in Chapter 9, "Lighting and Rendering." Press the 0 key to reset the stop, or exposure value, to zero. Note that after you go up or down in exposure value to a setting for a particular image, that exposure setting does not change as you subsequently click on different images, whether they are HDR images or not.

The buttons on the right side of the toolbar enable you to set the image you are looking at in the 2D view as a stamp, a stencil, or an image plane (see Figure 2.9 earlier). These are covered further in future chapters, but for now, just know the location of the buttons, and that this is where you can make the assignments. If you are looking at a 32-bit floating-point HDR or a grayscale extracted displacement map image and wish to differentiate the pixels that contain negative floating-point values, click the See Negative as Flat Color button (see Figure 2.9 earlier). Negative displacement is displayed as positive values by default, and using this option helps you troubleshoot problems in an extracted normal map by seeing the negative values in green.

If you are working on your image in another application such as Adobe Photoshop, or loading an update image from a digital camera to replace the one you are looking at, click the Refresh Thumbnails button (Figure 2.9) to see the latest saved version of the image.

To have your image zoom up, down, or fit the size of the 2D view of the Image Browser, click the Scale to Fit button. You can zoom in or out of the image by using the Ctrl and + or − keys, respectively. Hold down the Alt key and click and drag your mouse or tablet on the image in the 2D view to pan around an image that is zoomed bigger than what fits in the 2D view. You can also zoom up your image at a preset value of 1×, 2×, 3×, 4×, 5×, or zoom down your image to ⅔×, ½×, ⅓×, ¼×, ⅙×, ⅛×, or 1/12× by clicking the down arrow of the Zoom Ratio combo to the right of the Scale to Fit button (Figure 2.9). You can also type an arbitrary number in the combo box to zoom your image to that size.

To rotate the image in 90-degree increments, click either of the Rotate Image buttons to rotate clockwise or counterclockwise. Note that this does not rotate the image permanently; it just does so in the image viewer. Also note that if you do rotate an image and grab it as a stamp, stencil, or image plane, the rotated image will be grabbed even though the original remains in its original orientation.

When you click the Mudbox Community tab, your main viewport essentially becomes a browser window connecting you to the http://area.autodesk.com/mudcom website, where you can download and upload resources, view community posted tutorials, browse and rate the work of Mudbox community members all over the world, or submit some of your own work to get rated by others. Community users need to use their Autodesk AREA user credentials to log in to the site.

It is very important to understand the relationship between sculpt layers and subdivision levels. Sculpt layers are layers that contain differences in the surface of the model that have been sculpted specifically in that layer. Subdivision levels denote how many times the mesh has been subdivided to get more polygons, and, in turn, display more-granular detail. This relationship can be a source of frustration if you don't understand it well. I will go over it in a couple of places in this book. Read this section and go through the example in Chapter 3 until you are completely comfortable with the relationship between sculpt layers and subdivision levels.

Your model can be subdivided many times to add more polygons so you can sculpt finer details. You start with your model at level 0. As you subdivide, your model will progress to subdivision level 1, 2, 3, and 4, and so forth based on how much detail you need and of course what your hardware is capable of crunching. Each subdivision level you go up increases the number of vertices you have, by multiplying it by 4. So if you have 24 vertices in the model you start with at level 0, subdivision level 1 will result in 96 vertices, which is 24 vertices times 4. Level 2 will have 384 vertices, the 96 vertices from level 1 multiplied by 4.

You add a new subdivision level by clicking Mesh → Add New Subdivision Level in the menu or using the keyboard shortcut Shift+D. Doing so adds a subdivision level to your model and places your model at the newly created subdivision. You have to be at the highest existing subdivision level to be able to add a new level; otherwise, when you click Mesh → Add New Subdivision Level or press Shift+D, you will go up to only the next level that's already there. For example, if your model has four subdivision levels, and you are sculpting on level 3, if you press Shift+D, you will go to level 4 rather than add level 5. But if you are sculpting on level 4 and press Shift+D, you will add level 5. So if you are not at the highest existing subdivision level, Shift+D does not add a level, but has the same effect as Mesh → Step Level Up, or pressing Pg Up on the keyboard.

A sculpt layer is assigned one and only one subdivision level. However, multiple sculpt layers can have the same subdivision level. For example, three sculpt layers named scars, pores, and wrinkles can all be assigned subdivision level 5. This means you will sculpt these three skin details on individual sculpt layers, and these details will be sculpted on your model at the geometry detail provided at a subdivision level of 5 in their individual layers. However, you can work on these three sculpt layers only in subdivision level 5.

You can't go down a subdivision level while you are in a sculpt layer, because it is locked at the subdivision level it was created in. For example, if you are on the wrinkles layer at subdivision level 5 and you press Pg Dn to go down a subdivision level, you will get a No icon in front of the wrinkles layer in the Layers window, and you won't be able to sculpt your model until you either go back to subdivision level 5 or move off the layer by selecting another layer that is assigned the subdivision level 4. If you attempt to sculpt on a layer at a different subdivision level, you will get a dialog box explaining that the layer is locked at a specific subdivision level, and the options you have are either to be able to sculpt on this layer by going the subdivision level assigned to it, or creating or going to an existing layer that has the current subdivision level assigned to it.

You assign a level to a sculpt layer by selecting the sculpt layer in the Object List and by being at the desired subdivision level before making your first sculpting stroke on it. After you make that first stroke and the subdivision level is assigned to your sculpt layer, it is not possible to change the subdivision level assigned to that sculpt layer.

This can be frustrating because you can be on a layer but not be able to sculpt on your model. Before you start digging around in properties or thinking there is a problem with the software, look at the sculpt layer to see whether a red circle with a line through it appears next to the layer name. This symbol indicates that you are at a different level than the one to which the sculpt layer was assigned. That's why you are not able to sculpt on it. To fix this, either create a new layer for the level you are on, or click on the base-level mesh in the Sculpt Layers window.

To create a sculpt layer, do one of the following:

To delete a sculpt layer, do one of the following:

To duplicate a sculpt layer, do one of the following:

To select a sculpt layer, click on it. You will not be able to select multiple layers, but you can merge multiple layers by making sure they are visible and that other layers are not, and then choose Merge Visible from the Layers window menu. To show or hide a sculpt layer, click the little Layer Visibility dot or circle under the eye icon (Figure 2.11). To flatten or merge all sculpt layers into one, choose Flatten from the Layers window menu.

You can save a version of your sculpture, make changes to it, load the original back in as a layer, and use the opacity slider to blend the two sculpts. To do this, choose Import Layer from the Layers window menu, navigate to the .mud or .obj file, and then use the opacity slider to blend them.

You can also flip and mirror the layer along the x-, y-, or z-axis or the tangent by choosing the appropriate option from the list in the Flip and Mirror submenus from the Layers window drop-down menu icon. Chapter 5 covers mirroring.

The steps for operations on sculpt layers (such as selecting, deleting, duplicating, and showing and hiding) that you learned in the previous section all apply to paint layers as well, with one exception. When you create a new paint layer by selecting New Layer, you get the dialog box in Figure 2.12.

Figure 2.12. Create New Paint Layer dialog box

Here is where you choose the size of your images, which are referred to as maps, for the paint layers 256, 512, 1024, 2048, and 4096. These numerals refer to the number of pixels, and of course, a map is square so 2048 is actually 2048 × 2048 and is also referred to as a 2K map. You will mostly use 1K, 2K, or 4K maps depending on how much detail will be visible in your resulting output. In film or TV, close-ups require more detail; in games where textures have to be loaded and rendered in real time in the midst of action, you want to optimize memory usage by having smaller textures.

Figure 2.13. File formats

The Save As drop-down menu is where you choose the file format for your maps (Figure 2.13). The options are as follows:

You can save your images in four lossless file formats in 8-, 16-, or 32-bit depth, and all the images formats save four channels: Red, Green, Blue, and Alpha (RGBA). The four lossless file formats are as follows:

PNG Portable Network Graphics, a popular graphics format.

TIFF Tagged Image File Format developed by Aldus, now Adobe, is popular with the print and document imaging world.

TGA Truevision Graphics Adapter, or Truevision Advanced Raster Graphics Adapter (TARGA) is a ubiquitous file format for storing textures because of its ease of implementation.

OpenEXR OpenEXR is a high dynamic range (HDR) file format released as an open standard by Industrial Light & Magic (ILM).

As for which format is the best to use, it depends on the project or the company's production pipeline. Many game studios use TGA for textures, but OpenEXR is a growing open standard that has support for 32-bit depth and HDR. In this book, we will mostly be using TIFF, TGA, and OpenEXR.

You choose a channel type when you create a new paint layer. These are Diffuse, Specular, Gloss, Incandescence, Bump Map, and Reflection Mask (Figure 2.14). You can have multiples of these layers, and they are grouped in the Paint Layers window by channel (Figure 2.15).

Diffuse Specifies the base color of your sculpture. Think of it as the pure color in an environment that has no external influencing factors.

Specular Specifies the color of the specular highlight on the material. This is best described as the property that gives objects their shine. This is a grayscale image that specifies which parts of your model are allowed to show specular highlights (white and lighter grays) and which parts are not (usually black or darker grays).

Figure 2.14. Paint Layers window

Gloss Specifies the size of the specular reflection. It is also a grayscale image for which the darker the value, the smaller the size of the specular highlight.

Incandescence Incandescence simulates the emission of light by the material, independent of the lights in the scene. This paint layer indicates the brightness of the color on a material but does not affect or illuminate other models or parts on the scene.

Bump Map Bump maps give a fake sense of depth. Darker values appear to be inset, and lighter values appear to bulge out. You will not see the effects of a bump map on the edge of the geometry of a model because there is no displacement or chiseling in, it's just an optical illusion. The bump map is a grayscale image in which areas that are at 50 percent gray are flush with the surface of the model. Areas with darker colors are indented, and lighter ones appear to bulge out. The Bump Map is also the channel in which you can visualize an extracted displacement map on your model.

Normal Map The Normal Map channel, based on RGB colors, is the channel at which you can visualize an extracted normal map on your model.

Reflection Mask This is a grayscale image that specifies what part of your model reflects the environment.

Figure 2.15. Paint Layer channels

Note that the Mudbox Material used in the 2009 and 2010 versions of Mudbox had some additional channels such as Specular 2 and Gloss 2, and did not have others such as Incandescence and Normal Map. It also had some naming differences such as Bump Value instead of Bump Map. The channels in the older Mudbox Material are still supported with later versions of Mudbox to maintain compatibility; however, they are not available to you when you are creating materials:

Specular 2 A second specular that affects the fringes of the specular highlight. This setting is useful in low and oblique lighting situations.

Gloss 2 A second gloss component that affects the size of the outer regions of specular highlights. This setting is useful in low and oblique lighting situations.

Of all these channels, Diffuse and Normal are the only two in which color is relevant. Even though the others can be in color too, only their saturation is relevant, unless you want the specular highlight to have a particular hue. Note that you can have multiple diffuse maps layered on top of each other to represent the layers found in nature. For example, a face has subdermal and epidermal layers that you can paint; using the powerful layers capability of Mudbox, you can dial up or down the opacity of each layer to get your perfect desired blend of the two.

To merge or flatten paint layers into one layer, click Layers window drop-down menu → Merge Visible. This is a good practice if you are finished with the layers and don't need to make further adjustments and edits to them or their opacity, because this reduces the number of texture files and saves texture memory.

Some things to note when merging layers:

If you want to export paint layers, select them and choose Layers window drop-down menu icon → Export Selected. You can also import images as layers by choosing Layers window drop-down menu icon → Import Layer.

When you save your model (for example, torso.mud), Mudbox stores all your layers as image files in a folder (for example, called torso-files).

You can rearrange the top-to-bottom order of paint layers within their channels by dragging and dropping them in the Paint Layers window.

Paint layers can also be composited by using one of five blend modes that work similar to blend modes in Adobe Photoshop layers. Every layer starts out with the default Normal blend mode that you can change by using the blend mode drop-down menu. To determine the blend mode of a paint layer, click on it, and its blend mode will be indicated in the blend mode menu. The five blend modes available in Mudbox are as follows:

Normal The default blend mode for a paint layer. With this blend mode, the composite of all the layers will result only in the top paint layer in the layer stack unless you change the opacity setting to a number less than 100, or it has some transparent regions due to the image having an alpha channel that indicates what parts of it are transparent.

Multiply The value of each pixel in the layer is darkened by a value greater than or equal to the value of pixels occupying the same location on layers on top of it in the layer stack. It is useful for darkening an image, especially with an ambient occlusion map. Multiplying with white does nothing, while screening with black produces black.

Add The value of each pixel in the layer is brightened by a value less than or equal to the value of pixels occupying the same location on layers on top of it in the layer stack. Although Screen seems to do the same thing as the Add blend mode, the lightening effect produces no change in contrast because of the mode being applied in a linear fashion, producing a more extreme lightening result than Screen.

Screen The value of each pixel in the layer is brightened by a value less than or equal to the value of pixels occupying the same location on layers on top of it in the layer stack. The resulting effect is the opposite of the Multiply blend mode. Screening with black does nothing, while screening with white produces white.

Overlay Is a combination of Multiply and Screen. The Multiply blend mode is applied to a pixel if it is at the bottom 50 percent of the overall brightness of the image, and the Screen blend mode is applied to the pixel if it is at the top 50 percent. The base color on the layer is not replaced but is mixed with the blend color to reflect the lightness or darkness of the original color. This blend mode is useful for replacing patterns and colors while preserving the highlights and shadows of the base color.

Now that you have read a description of the Layers window, we will cover the Object List and Viewport Filters windows in the East Frame.

Add All and Add Selected enable you to add all the models or just the model selected in the Object List or 3D view. The Remove option removes the selected model in the Object List or 3D view from the target model name list.

If all the objects in the Target Models list share one UV tile, then when extracting maps for multiple targets, use the Generate One Map for All Targets option to generate one map for all of them.

If the target models use different materials or UV texture coordinates occupy the same UV tile location, use the Generate a Map for Each Target option.

When the Smooth Target Model option is selected, the map extraction operation calculations use a smoothed version of the target model. However, if you are extracting texture maps for games in which a faceted model is generally used, you can turn this option off.

When the Smooth Target Model option is selected, the Smooth Target UVs option smooths the interior UVs of the target model as well during the texture extraction. This feature is also useful for rendering software such as Pixar RenderMan, as this capability carries over to smooth the UV texture coordinates on a mesh during rendering to get better results.

As in the target models extraction options, Add All and Add Selected enable you to add all the models or just the model selected in the Object List or 3D view. The Remove option removes the selected model in the Object List or 3D view from the target model name list.

When Smooth Source Models is selected, a subdivided and smoothed version of the source model is used for map extraction calculations. This prevents jagged and hard edges from being generated when you apply the extracted maps to models in other 3D applications.

If you envision both a low-resolution version of your model and a high-resolution version in the same place, you will have faces from the high-resolution model intersecting the surface of the low-resolution model in many places. The Choose Samples option enables you to specify which value to use for the extracted map if an extraction sample intersects the high-resolution version of your model more than once:

A tooltip image comes up when you hover your mouse over the Choose Samples property. The tooltip provides an excellent graphical depiction of the three options.

The Search Distance setting indicates the distance that samples can span to find the source model. This range samples on both sides of the target based on the Choose Samples option. The Best Guess button sets the Search Distance, taking into consideration the distances of the bounding boxes for the source and target model. If the two surfaces are not too far apart, this option generates a useful estimate.

The Image Size indicates the height and width, in pixels, of the output maps. You can choose from the preset values of 256 × 256, 512 × 512, 1024 × 1024 (1K), 2048 × 2048 (2K), and 4096 × 4096 (4K).

Quality sets the granularity of the final ambient occlusion map. You can choose from the preset values of Fastest, Fast, Normal, Good, and Best. The higher the quality setting, the more number of shadow maps are produced and combined to generate a higher-quality map. However, this is at the cost of more time required to generate the ambient occlusion map.

The Base File Name field is where you indicate the name of the extracted map. AO(%s).bmp is used as a default if you do not specify a name, where %s is substituted by the name of the model. You can click the file button to the right of the Base File Name to bring up the Save As dialog box to set a directory and choose the file format (.png, .bmp, .gif, .jpg, .tif, or .tga).

If your model contains UVs outside the 0 to 1 range in two or more UV tile spaces, this operation automatically creates separate ambient occlusion maps corresponding to each UV tile by adding a suffix of the coordinates of the tile—for example, AOhead_u1_v1.tga and AOhead_u1_v2 for a model that has UVs in two adjacent tiles.

If selected, Preview as Paint Layer adds the generated ambient occlusion map as a new Diffuse channel paint layer. This lets you preview the generated map on the model. You can also use it to view ambient occlusion on your model without using the Ambient Occlusion viewport filters.

Shadow Map Resolution indicates the size of the shadow maps generated for the occlusion map calculations. You can choose from the preset values of 256 × 256, 512 × 512, 1024 × 1024, 2048 × 2048, and 4096 × 4096.

The greater the Shadow Map Resolution, the more detailed the occlusion map and the more time it takes to generate. In general, the Shadow Map Resolution should be set to the lowest possible value that produces an occlusion map of acceptable quality.

Shadow Darkness sets the brightness or darkness of the ambient occlusion map. Lowering the value from the default of 0.5 brightens the ambient occlusion map, and increasing the value darkens it.

Shadow Contrast sets the contrast between shaded and nonshaded areas of the ambient occlusion map. This value ranges from −1 to 1, with a default value of 0. Lower values reduce contrast, producing gray values in the map, while higher values increase the contrast, producing more black and white values.

Lower Filter values improve the overall sharpness of the finer details in the generated ambient occlusion map, while higher values help reduce some visible artifacts that sometimes are generated by the shadow maps.

Vector Space indicates the coordinate space for calculating vector displacement maps. The three options for vector space are as follows:

When the Bits per Channel option is set to 8- or 16-bit, turning on the Normalize to Search Distance option maps the results of the extraction samples to the 0 to 1 color space for displacement maps instead of the −1 to 1 range used for normal maps. As a default, Normalize to Search Distance is selected.

As with ambient occlusion, the Base File Name field is where you indicate the name of the extracted map. You can click the folder icon to bring up the Save As dialog box to set a directory and choose the file format (.png, .jpg, .bmp, .tif, .psd, .tga, or .exr), some with 8-, 16, or 32-bit depth.

Again, if your model contains UVs outside the 0 to 1 range in two or more UV tile spaces, this operation automatically creates separate displacement maps corresponding to each UV tile by adding a suffix of the coordinates of the tile—for example, disp_head_u1_v1.tga and disp_head_u1_v2 for a model that has UVs in two adjacent tiles.

Bits per Channel indicates the bit depth of the file type chosen in the Save As Type drop-down menu when you specify the name and location of the file to save.

Coordinate Space indicates whether Tangent, Object, or World coordinate space will be used to calculate the normal maps. Just like XYZ and UVW coordinates, the Tangent coordinate space on a face is set by the normal, tangent, and the binormal. A face normal is a directional line perpendicular to a surface and represents the internal or external orientation of each polygon face on a mesh. The tangent is a vector that indicates the slope of the polygonal face at a given point, and the binormal is a vector orthogonal to both the normal and tangent.

Object is the local coordinate space for the model in which the lighting of the detail shown from the normal map is based on the object itself. World is the overall scene coordinate space, in which the lighting of the detail shown from the normal map is based on the environment. Tangent is the default and the one you should use unless you have a specific need for the lighting on the detail of your model to be affected by itself or its environment.

The Compatibility field sets compatibility of the calculated normal maps with other 3D applications. The tangent space vectors are calculated using one of two methods, either the left-handed or right-handed method of determining the normal orientation. These methods determine the sequence of axes in a Cartesian coordinate system. For example, with the right-handed method, the thumb, index finger, and middle finger of the right hand are held so that they form three right angles, and then the thumb indicates the normal, the index finger the tangent, and the middle finger the binormal. Maya defaults to the right-handed tangent space setting, while 3ds Max defaults to the left-handed tangent space setting. Look at the settings for any other 3D application you use to determine its tangent space setting, and use Maya or 3ds Max as the setting to indicate right or left tangent space setting, respectively. Obviously, this does not matter if you use World or Object coordinate space because both coordinate systems are absolute.

Just as for ambient occlusion and displacement maps, the Base File Name field is where you indicate the name of the extracted map. You can click the folder icon to bring up the Save As dialog box to set a directory and choose the file format (.png, .jpg, .bmp, .tif, .psd, .tga, or .exr), some with 8-, 16-, or 32-bit depth.

As with ambient occlusion and displacement maps, if your model contains UVs outside the 0 to 1 range in two or more UV tile spaces, this operation automatically creates separate displacement maps corresponding to each UV tile by adding a suffix of the coordinates of the tile—for example, norm_head_u1_v1.tga and norm_head_u1_v2 for a model that has UVs in two adjacent tiles.

Bits per Channel indicates the bit depth of the file type chosen in the Save As Type drop-down menu when you specify the name and location of the file to save.

Export ASCII FBX is an option I usually select if I need to troubleshoot FBX export issues. I would leave this on as a default, but the ASCII version of FBX files take up a lot more hard drive space because the files are larger than their binary counterparts.

When turned on, the separate sculpt layers on the current subdivision level are exported as individual and separate blend shapes. When loaded into Maya or 3ds Max, separate blend shape targets can be modified with blend shape sliders very similar to the Layer Opacity sliders in Mudbox. The default setting for this is off, and the selected object is exported at its current subdivision when exporting it as .fbx.

When Fast Dry Brush is turned on, it accelerates the application of the Dry Brush tool. You should set this option to off only if the Dry Brush tool is not producing acceptable results because you will get better accuracy when the tool is slow to react to your stroke.