Working with Your Mesh
Group Loops and Mesh Extraction
ZBrush 3.5 Tutorial
by Ryan Kingslien

In this tutorial we will explore the following features:

• Mesh Extraction
• Group Loops

We will need to have a grasp of the following features to complete this tutorial:

• Transpose
• Masking

We begin in Photoshop with an alpha that is the shape of our object.  In this case, a door hatch for an old submarine.  This was created in Photoshop and is perfectly centered on a 1000×1000 pixel image.

In ZBrush, we want to select a PolyPlane and press Tool: MakePolymesh.  I also subdivided the resulting mesh to around a million polygons.

Import the hatch shape as an Alpha.

Press Tool: Mask by Alpha.  This will apply the image in the alpha palette to the model using the model’s UVs.

We convert this using Mesh Extraction in the Tool: SubTool menu.  Set Thick to 1.  If you object is too thick then lower this number.

Divide this once to give us some extra geometry to work with.

Get ready paint the porthole pattern by turning symmetry on for both the left and right of the model as well as the front and back.  In my case, I turned X and Z symmetry on.  You will also need to turn on L. Sym to line everything up correctly.

Select Alpha 14 and Drag Rectangle.  Press and hold CTRL and Click in the center but near the top and drag out till the hole is the size you want.  You may have to turn Focal Shift to -100.

Press Tool: Polygroup: From Masking Convert this to a Polygroup.

Repeat the masking and polygroup steps above to create groups for the hatch’s valve.

Delete Lower Subdivision, then press Tool: Geometry: GroupLoops.  Note, this creates a softer version of our model with new edge loops around our groups.  These edge loops will help us create cleaner edges when sculpting.  To smooth the model out less you can decrease the amount of Polish.

Its wise to clean up the new Polygroups.  I prefer to keep the groups specific to side plane, front place, etc.  This requires a good bit of time pressing CTRL+SHIFT and clicking on your model but it pays off in spades in the future.

Isolate different Polygroups and push and pull the forms to create the basic shape of the hatch.