How to Hollow a ZBrush Model and Control Wall Thickness

Author: Arndt von Koenigsmarck · Technical review by Paul Gaboury · Last reviewed August 2026 

Hollowing a model removes the solid interior and leaves a shell, which saves material, reduces weight and shortens print time. It only works well if the walls stay thick enough to print and handle. This guide covers how to hollow a ZBrush model for 3D printing and how to check and control wall thickness. It is part of the wider guide to ZBrush and 3D printing, and it assumes your model is already watertight, as covered in preparing a ZBrush model.

The quickest way to hollow a closed DynaMesh model is Create Shell. Set the Thickness value under Tool > Geometry > DynaMesh, then click Create Shell, and ZBrush generates an inner wall offset from the surface.

One important detail: the DynaMesh Thickness slider is not set in real-world units. The value is relative to the overall size of the model in ZBrush, so the same number produces a different real thickness depending on how large your model is. That is why setting real-world scale first and then verifying the result, covered below, matters so much.

For more control, or for models made of multiple parts, LIVE Boolean lets you create the inner void as a separate subtracted volume that you can shape and preview in real time. A clean way to manage this is ZBrush's Folder system: group the base model and the volume you are subtracting into a folder, then run SubTool > Boolean > Make Boolean Mesh on just that folder. The result is added as new SubTools to the currently selected Tool, so the rest of your model stays untouched and the operation stays organized. This approach is robust and predictable, and it pairs naturally with adding drainage holes or internal features while you work.

Because ZBrush does not work in units by default, wall thickness numbers only become meaningful once you define scale. Use ZPlugin > Scale Master to Set Scene Scale and resize your model to exact millimeters or inches. Doing this before you evaluate thickness lets the analysis below report real measurements rather than abstract values.

ZBrush's PolyPaint from Thickness analysis measures the distance between the outer and inner walls and paints the surface across a spectrum of colors, so you can see problem areas at a glance. With Scale Master applied, the ranges map to real millimeters:

• Red marks walls below your minimum range, meaning too thin to print safely.

• The mid-spectrum colors show increasing, safe thicknesses.

• The far end of the spectrum marks walls that exceed your maximum range.

Set the Min and Max Range values (for example 1 mm and 5 mm), click From Thickness, and correct any red areas by sculpting them up with the Inflate or ClayBuildup brushes. Turn on Backface Masking so you thicken the outer wall without disturbing the inner surface, then click From Thickness again to re-check.

For a quick spot check, draw a Transpose line across a wall and read the distance, which is handy when you only need to confirm one area rather than analyze the whole model. Adjust locally with a light Inflate or with ZModeler where needed.

If you hollow a model for resin printing, add one or more drainage holes so uncured resin can escape from the interior, otherwise trapped resin can cause suction failures or a hollow that never fully empties. A small subtracted cylinder placed in an inconspicuous spot does the job, and LIVE Boolean is well suited to placing these openings exactly where you want them.

Hollowing is not always the right call. Thin, delicate models, or small parts that need strength, can be better printed solid. Larger display pieces and busts are where hollowing saves the most material and weight. The general trade-offs, across any software, are covered in modeling for 3D printing, and if a model is too large to print in one piece, see how to split large 3D models for printing.

Next: bring the polygon count down for export in Decimation Master for 3D printing.