ZBrush FBX export slow or crashing? How to fix it

When ZBrush takes ages to export an FBX, freezes, or crashes, the cause is almost always the size of the mesh: a sculpt at its highest subdivision level can be millions of polygons, and the FBX plug-in has to write every one of them. The fix is to export less: set a lower subdivision level or decimate a copy with Decimation Master, send only the SubTools you need, and turn off SNormals for high-poly meshes. A few hundred thousand polygons export far faster, and it's plenty for anyone looking at the model on screen.

#Why ZBrush struggles with FBX

ZBrush is built to sculpt tens of millions of polygons in real time. Other programs, and the FBX format, aren't. When you export, ZBrush writes each SubTool at the subdivision level it's set to, so a sculpt that's smooth in ZBrush can turn into a file of several hundred megabytes. Three things make it worse:

• The highest subdivision level. Each level multiplies the polygons by four. One level down is a quarter of the size.
• Smoothed normals (SNormals). Computing smoothed normals on a dense mesh is slow. On ZBrushCentral, users with million-polygon meshes reported the export appearing to finish at once while ZBrush kept working for an hour; the advice was to keep SNormals off for high-poly meshes.
• Every SubTool at once. Exporting all SubTools at full resolution adds them all up, including the ones nobody needs to see.

#Get a light FBX out of ZBrush

1. 1

   Save first

   Save the project (File›Save As) before you try again. If the export crashes, you lose nothing.

2. 2

   Work on copies

   Duplicate the SubTools you'll export with Tool›SubTool›Duplicate, so your sculpt stays untouched.

3. 3

   Lower the polycount

   Either drop each copy to a lower subdivision level with SDiv under Tool›Geometry, or decimate it: open Zplugin›Decimation Master, tick Keep UVs if it has UVs, click Pre-process Current, then Decimate Current at 10–20%. ZBrush shows the active and total points at the top of the screen; on a quad mesh that's close to the polygon count. Aim for a few hundred thousand across the whole model.

4. 4

   Hide what you don't need

   In the SubTool list, hide SubTools that aren't part of this export.

5. 5

   Export with light settings

   Open Zplugin›FBX ExportImport, choose Visible, and turn SNormals off. Turn on Embed textures only if you made texture maps. Click Export.

#How light is light enough?

It depends on where the file is going:

To see the triangle count and wireframe of the FBX you exported, drop it on the free viewer. Nothing is uploaded, and it shows how dense each part is. See check polygon count and wireframe.

#If it still crashes

• Try OBJ instead. Tool›Export with OBJ writes the current SubTool and is simpler than FBX. If OBJ works and FBX doesn't, the problem is in the FBX plug-in, not the mesh.
• Export one SubTool at a time. If only one SubTool fails, the problem is in that mesh. Decimate it further, or try exporting it as OBJ.
• Close other programs. A dense export needs memory. A browser with dozens of tabs open competes for it.
• Update ZBrush. Exporter bugs get fixed in updates. A crash you can repeat every time on an up-to-date version is worth reporting to Maxon's ZBrush support with the file.

#Polypaint and textures

Lowering the subdivision level or decimating keeps polypaint, but on a much lighter mesh the colour can look softer, because polypaint is stored per vertex. If the colour matters, bake the polypaint to a texture on a UV'd mesh and export the FBX with Embed textures on. If the model arrives grey, see model looks grey.

#Send it for review

Once the FBX is light, upload it to MeshMarkup from Models. It's converted to GLB in your browser, and the person you send it to can turn it round and pin notes on it without ZBrush. The full ZBrush export walkthrough, with settings for FBX and OBJ, is in how to export from ZBrush.