ZBrush to Blender

From ZBrush Info

This guide will provide a reference for working with importing and exporting models between Zbrush & Blender users.

• It isn't meant to teach you how to use Zbrush or Blender. There are more than enough references here for Zbrush: ZBrushInfo_Home I also highly suggest you read the ZBrush2_Practical_Manual if you're a beginner.
• Visit http://www.blender3d.org for info on Blender and a manual that you can download. Also visit the Blender user forums if you need further help: http://blenderartists.org/forum/

Contents 1 Starting In Blender 1.1 Preparing the Blender Model 1.2 Exporting the Blender Model 1.3 Working in Zbrush 1.3.1 Importing the Model 1.3.2 Subdividing the Mesh & detailing 1.3.3 Changing the UV Mapping in Blender 1.3.4 Notes on Adding Geometry & Models Created in Zbrush 2 Normal Map Placement in Blender

Starting In Blender

For this part of the guide, we'll start with a model in Blender, and simply add detail in Zbrush.

Preparing the Blender Model

• Blender currently has limited support of Ngons. It's important to note that Zbrush does not support Ngons, so most likely this won't be a problem at all for you, but if so, make sure you have converted to quads or triangles.
• You can work in Zbrush in either quads or tris, however quads are preferable as they give a more cleaner work flow that I've noticed, especially when you subdivide many times.
• If you plan to have readable UV maps and do no more work to the model(except in subdivision details in Zbrush), now is a good time to UV map your model!
• If you plan to not only create the subdivions & detail in Zbrush, but to also possibly add geometry in Zbrush, then you'll want to hold off on the UV mapping. More details on this are described below.

Exporting the Blender Model

• Zbrush can have either .obj or .dxf files imported. The .dxf format does not save UV's, so .obj is what we will use.
• Shown below is an image of the settings of the .obj export packed with Blender. These are the options I have set when exporting. You may want to experiment with others, but these are the ones I've found to be the best, that work thus far.

Working in Zbrush

• Please read the sections below fully, because depending on what you want to do you may have to plan your course of action better. There are some idiosyncrasies when it comes to UV mapping when you add edge loops in Zbrush and exporting/importing from Blender<->Zbrush.

Importing the Model

• Go to Tool:Import.
• Note that if you want to import more than one model into a scene, and still retain the other model, or tool, you imported, you'll need to click on another tool in the tool box, one of the defaults you won't be using. Otherwise Zbrush will replace the next tool you import with the one you've currently selected.

Subdividing the Mesh & detailing

• To subdivide your model go to Tool:Geometry:Divide. Each time you press Divide, you gained a new subdivision level. Read more about the subject of subdivion here: Polymesh_Tools
• You can then add details to any subDivison level by using the available tools and/or Projection Master.

Changing the UV Mapping in Blender

• Zbrush does not support full manual UV editing, however it does have a few different automatic uv mapping techniques that may be of use to you. More info here: Tool:Texture_Subpalette
• If all you have done is subdivide and detail, you can edit the UV's in Blender. It is much easier to have done your UV mapping properly from the start however.
• Put your model in Subdivision level 1-it MUST be in this level. Tool:Geometry:SDiv 1
• Export the model as .obj having options obj, txr, qud, mrg checked, Scale at 1. Go to Tool:Export. Only .obj will keep your UV maps intact!

• Import the .obj file into Blender.
• VERY IMPORTANT: You must NOT alter the mesh in any way! Do not rotate it at object level or at edit level. Do not move, add, subtract ANY vertices or polygons! If you do you will not be able to import it back into Zbrush correctly! Keep it exactly where it lands when you import it.
• Make any changes and fixes to the UV's you need to using the UV editor.
• Export .obj file from Blender.
• Back in Zbrush, make sure you have the model you were working on active, and set to Subdivision level 1.
• Import your new .obj file by going to Tool:Import. Nothing should be checked, Tri2Quad & weld should both be at 0.

• If you followed the above steps your model with the new UV's should have imported correctly. All subdivision levels should look just as they were.

Notes on Adding Geometry & Models Created in Zbrush

• If you want to add geometry in Zbrush you must use Edge Loops. You can read more on edge loops here: Box_Modeling_and_Precision_Texturing
• Adding Edge Loops, or using a model created in Zbrush, conflicts with the importing & exporting of .obj files between Blender & Zbrush. There are work arounds however, but it does mean that if you have done UV mapping before now and need to edit it, you will have to redo it in Blender completely. The reason for this is because instead of exporting an .obj file from Zbrush, we're going to export a .dxf.
  • .dxf files only save the mesh, not UV's.
  • It is unknown to me why adding edge loops causes problems, but it does.
• Export your mesh by first putting it in subdivision level 1, then go to Tool:Export, and check the options Dxf and Qud

• Import the .dxf file into blender, fix the uv's, remember to not move the mesh/vertices in any way.
• Export as .obj from Blender.
• Import as .obj into Zbrush. Make sure you have your model(tool) active in Zbrush at subdivision level 1 before importing.
• All your higher subdivision levels should be intact!

Normal Map Placement in Blender

• You can generate your normal map in Zbrush. Info on how to do that is found here: Tool:NormalMap_Subpalette
• You will need to flip the normal map vertically, because Zbrush flips the UV's. You can do this in an image editor, or you can do it from Zbrush by going to Preferences:Importexport:NormalMapFlipVertical.

• In Blender, select the object you want to put the normal map on.
• Go to the buttons window, choose shading(F5), then Material buttons.
  • In the Links and Pipeline box, click Add New, or choose from an existing material you have in your scene.
  • In the texture box, click on Add New, and name it normal(or whatever you'd like).
  • In the Map input box, make sure UV and Flat are checked.
  • In the Map To box, make sure Nor is checked and highlighted as yellow(click on it twice), and also make sure the Nor slider has full influence.

• Next, go to the Texture buttons(f6)
  • Make sure Texture type is set to Image in the Texture box.
  • In the image box, click on Load image and load your normal map. Check the Normal Map button.

• And that's all there is to setting up a normal map in Blender! You can then proceed to place your material and shader settings for rendering.