Importing and Detailing a Mesh in Zbrush 2

This tutorial is a step-by-step breakdown of the process of importing a mesh from a separate application, like Alias Maya or 3DSMax, so that it can be detailed in Zbrush. The focus of this tutorial is to acquaint a relatively new user to the Zbrush workflow, which many find initially confusing.

The first thing to remember is the location of your files. This tutorial assumes you have already exported your model as an .obj file (.dxf is supported, but UV coordinates are not stored in .DXF) from Maya\3DS Max\Lightwave\etc. The mesh should have been properly built and UV-mapped prior to bringing it into Zbrush. Without harping on this too much, it's important to know Zbrush favors quadrangles over triangles. Zbrush will not accept an n-gon, it will be converted into a triangle or quad upon import. If possible, build your mesh using quadrangles as much as possible because quads subdivide more predictably than triangles - and most of the detail-work in Zbrush is done on a highly-subdivided mesh. If the mesh is all triangles when it is imported and subdivided in Zbrush, the surface will have lots of pinches and lumps, making accurate detailing very difficult. The occasional judiciously-placed triangle isn't a big problem, but persistent triangulation will result in an inefficient and mostly unusuable mesh for detailing. With the mesh properly constructed and UV-mapped, it can be successfully imported into Zbrush 2.

After starting Zbrush, click on the "Tools" menu. In the Tools roll-out, you'll notice a star-shaped icon. This is the Polymesh3D tool. Zbrush 2 uses this tool to parse a mesh made in another application into Zbrush. Look down the Tool roll-out to the "Import" sub-menu. Click on the roll-out to see your import options. For now, just click the "Import" button. Leave the settings at their default position.

Next, browse through directories until you locate the .obj file you want to use. Select the file and click "Open."

It probably looks like nothing happened, but, in fact, the .obj file is now loaded into the Polymesh3D tool. However, it has not been placed in the Zbrush work area.

Place your cursor over the work area/canvas (the lighter grey-colored square) and click+drag. You will see your mesh draw (probably upside down) and grow as you continue to drag.

After the intial click+drag, tap the "T" key. It's the first thing you should do after drawing the mesh. Clicking the "T" key puts the mesh into Edit mode where you can rotate, move and scale the mesh. If you don't do this, the mesh will be embedded in the canvas and will be unavailable for editing. This frustrates a lot of new users because most anticipate the mesh to be editable after they let go of the initial click-drag. With Zbrush, you have to put the mesh into Edit Mode first. If the mesh is in edit mode, you can quickly drop it by tapping the "T" key a second time. This drops the model, or "tool" as it is called in Zbrush, back onto the canvas. Occasionally, you'll drop the tool onto the canvas and no amount of tapping "T" will pick it back up. What happened? Odds are you accidentally clicked another key or tapped your mouse button, thus telling Zbrush you don't want to pick the tool back up. Basically, you said to Zbrush, "I'm done with this tool. Leave it where it is." Don't panic. You didn't loose access to the tool, you just imbedded an instance of it into the canvas. In fact, the tool is likely still a mouse-click+drag away. The embedded instance is probably annoying to look at, so tap "Control+N" to clear out the canvas. Get used to this. You'll do it about a million times.

With the model in Edit Mode, expand the Tools>Geometry rollout and click the "Divide" button. This will subdivide the mesh Each time you click the Divide button, Zbrush quadruples the density of the mesh. Depending on the complexity of the model, Zbrush 2 can create between 5 or 6 levels of division. To create surface detail on an imported mesh it is necessary to create such a dense surface. You will use the tools in Zbrush 2 to sculpt in detail on the dense mesh much like you would sculpt the detail in clay. Pressing the Ctrl+D keys simulatneously is an effective shortcut to clicking the "Divide" button.

At this point, while in Edit Mode, you can begin using the Standard Edit Brush to push or pull details into the mesh, at any level of detail. While Zbrush can simultaneously paint color, material values and depth, we're going to focus on just depth. If you look under the menu line at the top of the Zbrush 2 GUI, you'll see another line with many buttons. It's important to notice this line because it houses the Material, Color and Zadd and Zsubtract keys, among other tools. You can turn on or turn off these options by clicking on the buttons.

The depth tools are amongst the most dramatically different tools available in Zbrush 2, allowing you an unprecendented level of artistic freedom to modify the surface of a model. Zadd and ZSub(tract) push or pull the mesh depending on which function you select. Zadd pulls the mesh out while Zsub pushes the mesh in. You modulate the strength of the push or pull by adjusting the Z intensity slider. Pressing the "Shift" key while you work turns the red circular brush cursor blue. When the brush is in Smooth Mode, you can "smooth out" the mesh by painting wherever you want.

Using the Standard Edit Brush combined with Zadd, Zsub or Smooth is the main workflow for creating the rough blocking stage of the mesh. While the Standard Edit Brush is the default tool, other brushes are also available and yield different results. For example, the Inflat Edit Brush, although initially similar to the Standard Edit Brush, pushes or pulls the polys of a mesh along the surface normals of the mesh, thus giving a slightly different look than the Standard Edit Brush. Layer Edit Brush produces a different effect as well. Each of these brushes give you something different. By experimenting with these brushes, you'll begin to understand how and when you can use them.

It's important to remember you can work with the mesh at any level of subdivision. You can quickly shuttle between each level either tapping the "D" key to shuttle up in Subdivisions or by tapping the "Shift+D" key to shuttle down. The brushes work at any level. Adjust the strenght of the Zadd and Zsub while you work with each level.

You should spend most of your time detailing the mesh using the Standard Edit Brush. Most of the initial surface detail can be applied by judiciously using the tools in the Transform menu. At some point, though, you'll want to add certain details that can best be created by using the Projection Master - Zbrush's micro-detail painting tool. Press the "Projection Master" button at the top left-hand side of the screen or press the "G" key to invoke this tool.

When you start Projection Master, you'll be greeted by a screen that forces you to make some decisions before you begin. The screen gives you the option of painting Color, Shading and Material, in regards to surface color. Projection Master also affects surface depth with deformation and normalized option-check boxes. When you are only concerned with surface modification (not color or materials) make sure the color, shaded and material boxes aren't checked.

When you are only concerned with surface modification (not color or materials) make sure the color, shaded and material boxes aren't checked. If you do have them selected and click "Drop Now" Zbrush will ask you if you want to create a texture, assuming you don't already have a texture created. For now, don't worry about color. Click "Cancel Projection," then click the Projection Master button again and make sure "Color," "Shaded" and "Material" aren't selected and "Deformation" and "Normalized" are selected. This tells Zbrush, you only want to work with surface depth.

Once you've started Projection Master, you'll notice a couple of things. The most obvious thing is you no longer can move, rotate or scale the tool. Projection Master locks the tool into one view in order to work. To pick the model up again, press the "G" key. Rotate, move or scale the tool to a different view and press "G" to drop it back into Projection Master.

Back in Projection Master, you can now begin to paint details on the model. The first thing you want to do is to select a Tool from the Tool menu. The Tools are quite varied and you'll need to experiment with them to understand what each can do. Most of the tools work with Color, Material, and Depth Simultaneously, but some affect only color. Again, experimentation is the only way you'll ever know what the tools do, so play with each one of them to see what each tool does.

After selecting a tool, you need to think about which Alpha you will use. Zbrush offers a very good default selection of Alphas. For this tutorial, think of Alphas like brushes in Photoshop or Painter, creating the pattern of color or depth deformation on a surface. Alphas are one of the most versatile tools in Zbrush and can be used in a variety of ways, but for now, just think of them as different brushes.

Once you've selected the Alpha, pick a stroke. The default stroke you start out with will differ from Tool to Tool. For instance, the Deco Brush Tool uses the DragRect stroke by default, whereas the SingleLayerBrush uses the Dots stroke by default. Experimentation is again the key to understanding what each stroke, in concert with the Tool and Alpha, will produce in Projection Master.

When you need to resize a stroke, there are a couple of ways to increase or decrease the brush or stroke size. The easiest way is to increase or decrease the "Draw Size" slider at the upper right-hand portion of the screen. The same effect can also be accomplished by tapping the "[" or "]" keys, although the brushes will scale up or down in sharp increments. Another way to resize the stroke or brush size is to tap the "S" key. This invokes a small window with the "Draw Size" slider box where your cursor is located. You can adjust the brush size easily with this tool. Alternatively, you can tap and let go of the "Space" bar on your keyboard to invoke a hot-box with a miniature version of the control panel located at the top of the screen, just under the menu. This hot-box has all the functions available in one handy console and I use it almost exclusively.

After you have your Tool, Alpha, and Stroke selected, you can begin painting details in Projection Master. I've found my workflow in Projection Master breaks down as follows: Paint a few strokes, pick up the tool, see how it looks on the model. Paint a few strokes, pick up the tool, rotate the model around and see how it looks. Wash, rinse, repeat. Because painting in Projection Master is an approximation, I don't always get exactly what I see when I pick the mesh up. The more detailed the mesh, the more closely I'll get to what I see in Projection Master.

As you add more detail, you will find that you use all the tools together. You won't just work in Projection Master. You won't just work with Standard Edit Brush. You'll use a little bit of everything. You will end up using every tool in the arsenal to achieve the finished product.

With the detailing on the mesh finished, you can now extract a normal map. Zbrush can bake a normal map very quickly by comparing a the high-resolution/frequency mesh with the low-resolution mesh. The first step in the process is to take a snapshot of the high-res model while it is still in Edit Mode.

After you take the high-res snapshot. Change the level of detail to the lowest setting. The snapshot of the high-res mesh is stored in memory, but Zbrush also embeds the snapshot in the canvas - resulting in a overdraw of the low-res model in Edit Mode and the high-res model snapshot. This is annoying. Clear the canvas by tapping a combination of the "Ctrl+N" keys simultaneously. The high-res embedded image will be cleared.

Most of the time, you'll probably make a tangent space normal map. To make one, go to Tools>Geometry>NormalMap. Expand the NormalMap roll-out. Make sure "Tangent" is selected. Make sure you have the right resolution for the final normal map by entering it in the resolution field to the right of the "Tangent" button. If it's turned on, turn off the "Adaptive" button (causes the Normal calculation to be longer with no noticable quality benefit). Click the "Make NormalMap" button. A normal map will be baked and put in the open texture slot. You'll see it displayed immediately on your model.

The final step in the normal map extraction process is to export the image. Click on the Texture menu. Zbrush draws the normal map upside-down, so you'll need to flip the image vertically. Do this by clicking the "Flip V" button. Next, make sure the image is the right size. Then press the "Export" button. Pick a file format and a destination directory. Give your image a proper name and click the "Save" button. Done.

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