PolySculpt

This short tutorial is to answer a question by Jbshorty on my forum Polyloop.net: after creating a base mesh in Hexagon, he had a problem of alignment of his radial symmetry, which wasn’t centered at all. After looking at the model, I found the problem. It was not a bug from Hexagon or ZBrush, but a problem because of the form of the model.

This is the original model:

As you can see, the brush dots are offset down the model. Using the local symmetry, or trying to use the posable symmetry doesn’t work for a simple reason: ZBrush is using the bounding box to compute the symmetry and on this model, the center of the object isn’t at the center of what we think it is, because of the two ‘arms’ on the left and right of the model. Then, on the screenshot, the brush have the good position in the space, not the model.

Then, in this small tutorial, I will show you how to fix that, by changing the pivot point in ZBrush, from the first step of importing the model.

1. Import and Radial Symmetry

To import the model, if you already have a 3D model (a ZTool) loaded, in the Tool palette, load the Polymesh3D model (a 3D star) and click on import. Choose your OBJ file to load. You should have something like that:

Then, the first thing to do to sculpt such object in a symmetrical way is to activate it. Then, go in the Transform palette, activate the Symmetry, choose the Z axis only (the depth is most of the time Z) and click on the (R) button, to switch to Radial Symmetry.

The screenshot below shows these settings.

As described in the introduction, the radial symmetry is not centred where we would like it to be.

2. Preparing the model for the new pivot point

It’s time to do some changes on the model to do the final step. First, switch to Orthogonal mode. By default, ZBrush is in orthogonal mode, not in perspective. But for the next step, you must be in orthogonal. To check that, go in the Draw palette and see if the button “Persp” is disable. The perspective shortcut is “P”.

Then, switch to a side view and while rotating, press the Shift key: ZBrush will snap the rotation to 90° angles. Choose a side view.

Now, we will need to display only a selection of polygons, the extremity of the extrusion. While on this side view, press CTRL+Shift and with the visibility marquee, select the last loops of polygons like on the screenshot below:

When releasing your click, only a cap should be visible. Take care of having a uniform selection of polygons, I mean, having a full loop of polygons around the cap. If you selection isn’t symmetrical, start again this step.

3. Setting the new pivot

Now, the main step of this tutorial! Let’s define a new pivot: in the Transform palette, click on the S.Pivot (Set Pivot). This action will redefine the pivot of the visible polygons. As our object have only the cap visible and because this cap is fully symmetrical in the X and Y axis, the new pivot will be exactly in the center. To prove that, when you will clicking on the button, the cap will move in your document.

Now, unhide the polygons of the other part of the model by doing a CTRL+Shift click in an empty part of the document and voilà! Your brush is now fully radial symmetrical!

Change the radial count in the Transform palette to 3 and you can start your sculpting!