How do you invert polygons in ZBrush?

To invert polygons (flip faces) in ZBrush, use the ZModeler brush and the "Flip Faces" action.

Here's how:

1. Select the ZModeler Brush: Ensure you have the ZModeler brush selected.
2. Hover Over a Face: Hover your cursor over the polygon you want to flip. This will activate the ZModeler context menu.
3. Access the Polygon Actions: Press the Spacebar. This will open the polygon action menu specific to the ZModeler brush.
4. Choose "Flip Faces": Select "Flip Faces" from the menu options that appear.
5. Define the Target (Optional): You can define the target for the "Flip Faces" action. The targets allow you to specify which faces are affected by the operation. You can target single faces, connected faces, polygroups, etc. If you just want to flip the face under your cursor, no need to adjust the target.
6. Click a Face (if needed): If you've chosen a target that requires you to select a face, click the face you want to apply the "Flip Faces" action to.

This process effectively reverses the normals of the selected polygon(s), inverting them. This is useful for correcting surfaces that appear inside-out or for achieving specific artistic effects.