Use Sculptris mode on a huge mesh

[logiclrd]

I have models from a 3D Scanner that require some fixup. Sculptris mode is super useful for this editing, but the models have ~48M polygons, so Sculptris won’t activate (seems to be possible to increase the limit to 10M but no further). It looked like a possibility to use Split and Merge to separate off part of the mesh, work with it in Sculptris mode, and then join it back together, but the join isn’t seamless; when I later decimate the mesh and convert the vertex colouring to a texture, scars become visible every place that the model was Split and then later Merged.

How can I do the kind of fine editing that I need without sacrificing the quality of the mesh and without introducing scars all over the place?

Here’s an example where I used Split and Merge quite heavily to track down exactly where the mesh had errors (as identified by Geometry > MeshIntegrity). The model looks okay at full resolution in ZBrush:

But, after decimating it, every place I used Split and Merge becomes very visible:

[zber2]

Hi @logiclrd

Make sure you are meeting all the Sculptris Pro Requirements.

[Spyndel]

Hi @logiclrd!

I’m sorry for not getting back to you sooner! The company has been focused on the release of ZBrush 2025 and ZBrush for iPad that were released today.

Before we get into this I just wanted to make sure you were familiar with the process for detail projection. Using one of the various methods you can always project the detail and vert color from a previous version of the mesh to a newer model with optimized topology. So you never need to worry about really losing detail as long as you have the original model!

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That said there are a few different things at work here:

@logiclrd

Sculptris mode is super useful for this editing, but the models have ~48M polygons, so Sculptris won’t activate (seems to be possible to increase the limit to 10M but no further).

Sculptris is generally intended as a tool for rapidly developing form up to a medium/medium-high level of detail. After a certain point where the form is no longer expected to frequently change, it becomes less useful and a traditional multi-res with traditional displacement painting workflow becomes more so. ZBrush is optimized to display and navigate with models in this form while keeping performance high, whereas sculptris topology will hit practical performance limits at a single level of subdivision. The process of creating cleaner base topology and subdividing also tends to purge the model of the sort of mesh integrity issues you refer to if they are present.

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Regarding seams, this will generally occur if you sculpt over the edge of a piece of mesh separately from a surface it’s supposed to form a continuous surface with. You should try to either keep sections of mesh that are supposed to be one unbroken surface together in the same subtool or be prepared to do some cleanup.

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So the goal may not be to directlly alter the existing topology. It may be to derive a newer, cleaner topology from it, subdivide it, and project the detail from the original onto the new. This is often done with Zremesher to create a new low poly quad base mesh of decent quality for many purposes. However, if you’d like to directly edit the topology of your existing model, I would recommend the following:

1. Decimate first. Decimation Master is very good at crunching poly count down while maintaining detail. The drawback is that it creates triangular, sometimes extreme topology that doesn’t work well for all purposes. However you will be working with Sculptris tesselation anyway so this is less of an issue.

2. The Tool> Geometry> Tessimate feature can be good for further fine tuning mesh density. It allows you to locally control polygon density by masking off areas you don’t want to affect. Take polygons away from areas of low detail and deliver them to areas with fine detail.

Isolating an area of mesh is often as easy as making a quick mask stroke, then Ctrl-clicking the canvas to invert it so the mask protects everything but the stroke area. Polygroups can also be very helpful in quickly selecting or hiding areas of a mesh within a single subtool.

Using these tools you can probably put the model within range of Sculptris Pro pretty easily. If not, you, can always use the mesh to create a new base mesh target for detail projection.