The Alpha > Make 3D sub-palette allows you to create a 3D mesh from the selected alpha.
The Mesh Resolution slider determines the polygon-resolution of the 3D object which will be generated when the Make 3D button is pressed.
The Mesh Depth slider determines the Z-axis scale of the 3D object which will be generated when the Make 3D button is pressed. If this value is set to 0, ZBrush will calculate the depth automatically.
The Mesh Smooth slider determines the smoothness of the 3D object which will be generated when the Make 3D button is pressed. If this slider is set to 0, the 3D object is created using cubical skinning — the object appears to be composed of many tiny cubes.
The Double-Sided button affects the 3D object which will be generated when the Make 3D button is pressed. If this button is pressed, the object will be composed of two mirror-image extrusions of the selected Alpha, joined back-to-back. If un-pressed, the back side of the 3D object will be flat.
Press the Make 3D Mesh button to convert the current Alpha to a true 3D (polygon-based) object. This process is sometimes called Alpha Skinning. Conversion makes use of the Mesh Resolution (MRes), Mesh Depth Resolution (MDep) and Skin Smoothness (Smt) sliders, as well as settings to determine the complexity of the mesh. The converted object will be added to the Tool palette, where it can be further transformed, sculpted, incorporated into ZBrush artwork, or exported to other 3D modeling programs.