Workflow: Altering the base mesh...

#1

I’m relatively new to ZB and at this stage I’m really just trying to sort out the workflow. My question is about making revisions to a base mesh.

Say I’m working on a character. I make a low poly cage in MAX or Maya and do my best to get the edge loops just so. I import the character into ZB and start dividing and sculpting details. At some point down the road for whatever reason (design changes, inspiration, sheer lack of foresight) I realize that I really need to cut some new edge loops into the base mesh in order to create some new details - but I’ve already done a lot of sculpting elsewhere on the model. What do I do?

I know I can export my mesh at level 1, make changes in my base modeling app and then import the result - but that the vert count needs to match so that’s not really going to work for adding detail.

If I think of the newly edited base mesh as a completely different model, is there away to apply the sculpting data from one model to another? I assume that if the two model’s UV’s are at least similar this could be an option?

Or do I need to edit the base mesh IN ZB?

#2

Hey Tetsuo239

There are many ways to achieve what you’re after, both inside and outside zbrush. One great thing about zbrush is that your vert count/order don’t have to match for you to transfer high res detail to your new mesh.

You specifically asked for a way to add edge loops or retopologize areas of a base mesh while retaining detail. This is the simplest problem to solve. Here are 2 ways (of many) to do it:

Before doing anything, always remember and obey the following 2 rules:

Rule 1: While your model is at it’s current HIGHEST subdivision level, go to the Deformation menu (under Tools) and click Unify. This will rescale your model so that it imports and exports at the exact same size. (This is easiest to do when you’re working with no subtools.)

Rule 2: You may add edge loops, or change surface geometry flow in any program, but your new geometry MUST be the same overall shape as your old geometry. Adding arms, legs, or other large volumes of geometry requires a different process. Right now we’re just changing topology flow, and transferring your high res details to the new topology.

Method #1

-Lower your model resolution down to it’s lowest level.
-Export your model as an obj file.
-Import the obj into your preferred modeling program.
-Add edge loops, or make surface geometry changes. (Do not rescale the model.)
-Export back out as an obj file.
-In Zbrush, make sure your original model (tool) is still on it’s lowest subdivision setting, then use the import button in your tool menu.
—Zbrush will ask if you want it to transfer high res detail to your new geometry. Click yes.

Zbrush will subdivide your new geometry to match your original, and your original details will be present on the new topology. Your old topology no longer exists except in what ever files you already have saved to your hard drive. (You can also use the undo command if anything went wrong with the import.)

Method #2 (a bit longer, but it can help with other tasks)

-Do everything above, except when you’re ready to import your new geometry, have a default zsphere tool selected instead of your original model.
-Import your new obj topology. (The zsphere is now replaced by your obj.)
-Select your original model, then open your Subtools menu.
-Click the Append button, then select the topology you just imported. (You should now have both your original model and your new topology in the Subtools menu.)
-In the Subtools menu, make sure that both tools are visible, and make sure your new topology is the active or selected tool.
-Subdivide your new topology until it has at least the same number of subdivision levels as your original model.
-Click the Project All button in the Subtools menu.

Now your original model and your new topology should exist in the subtools menu with high res detail on both. You can delete your original, or keep it around for a backup subtool.

There are many variations on how to transfer detail, but I feel these two are the usually the best.

You can also retopologize in Zbrush, or even simply add edge loops, but that’s another process.

Also, if you need to add volumes (arms, legs, etc) and also preserve esisting high res detail, there are processes for that as well. Not sure exactly what you need done.

Edit: (clarity)

#3

Thanks, this is amazing. I couldn’t have hoped for a more thorough response. As I said, my goal here is really to gain understanding of the process, and that’s what you’d provided.

Since you bring it up, I’d love to know more - or at least which direction to look in - about making major changes to the shape of the model (adding arms, legs, etc).

#4

No problem. More info incoming.

Heads up: As you work and learn more, you’re almost always going to find new problems, and new workarounds. Every step by step process I’ve ever used has failed at one point or another, but they help you figure out new solutions.

As for adding new volume to a single model, here are a few possibilities:

Rule: All new volumes/additions need something of nearly equal volume to press/project against, if you intend to transfer high res details from one model to another. Ex: A hand needs a hand to project against. A rock needs a rock. Objects receiving details from other objects cannot have parts floating in open space, or they’ll explode.

Lets say we want to add an arm. I’m going to go through many of the possible steps, but this will probably seem convoluted to new users. It gets fast and easy with experience.

Method #1: Zspheres

-Make sure your main model is active.
-Append a Zsphere as a subtool.
-Make your Zsphere the active subtool.
-Activate Transparency mode, and Ghost Transparency. (Your mesh goes white transparent, and you can click through it.)
-Build an arm from Zspheres and make it an Adaptive Skin when you are finished. (The adaptive skin will be a separate model / tool.)
-Hide the Zsphere arm.
-Append the new adaptive skin arm as a Subtool. (Adaptive skins always begin with the name “Skin_” so you can tell them apart from your Zspheres or other models.)

-Polygroups > Group Visible for the body. Then Group Visible for the arm. (This step helps us merge and separate both pieces as needed later on. If you want to check that it was done properly, click the PolyFrame button. When active, each subtool will be one solid color with black geometry lines. If you see multiple colors on a single piece, click Group Visible again.)

-Deactivate the Wield button. (Subtool option)
-Lower all visible subtools to subdiv level 1.
-Click Merge Visible. (Subtool option)
-Now bring your subdiv levels all the way back up. (You may also subdivide the arm a few times, if you wish. It may help later.)
-Click Merge Visible

We should now have 2 brand new models in the Tool menu area. One merged low detail model, and one merged high detail model. The merge option helps us export multiple subtools as if they were a single object.

-Select the low poly merged model from your Tool list.
-Deformations > Unify
-Select the high poly merged model from your Tool list.
-Deformations > Unify

Unified models import and export without changing size during the process. This will save us much pain later on.

-Export the merged model, then import it to your favorite modeling program.
-Manually connect the arm geometry to the body, or separate them (different word for every modeling program) and create a low poly cage around your new arm.

The overall goal is simply to have an arm and a body attached as a single mesh. Don’t scale or reposition anything. We want it to closely match the shape we started with.

-After you’ve finished attaching the arm to the body, delete any unused geometry. (If you created a new cage around the imported arm, for example, delete the original arm. We just want one solid mesh.)
-Export as an obj

-In Zbrush select a new zsphere.
-Import your new mesh. (This will replace the zsphere)
-Select the high detail merged model. You’ll know if you have the right one because it should have no subtools in the subtool list.
-Append your freshly imported model as a subtool.
-Select the appended subtool to make it active.
-Subdivide enough times to create enough geometry for your original details to transfer.
-Subtools > Project All

If everything went as intended, you now have a single solid mesh with high details and a new arm.

Broken down concept: (no details)

-Create extra geometry in Zbrush.
-Merge parts so that they can export together.
-Wield geometry outside of Zbrush.
-Bring back to Zbrush for detail projection.

This is not the only way to do things though. Far from it. However, once you understand the whole process, it generates few if any errors at all.

Let’s say you don’t want to mess with Zspheres, though. Maybe you want to create the arm 100% outside of Zbrush. Cool.

Things to remember:
-The rule! See the top rule of the page. :slight_smile:
-Everything has to line up, so you may end up rescaling things in Zbrush, before detail projecting. It’s a pain.
-If you add volumes to a model in Maya, Max, etc, export the full model, but also export separate models of the new volumes themselves. You can append the separate volumes as subtools, so you can project your new solid mesh onto a series of equal sized parts. Again, you may spend a lot of time lining things up so you can project properly.

Zbrush retopology tools are also an option. Add parts, then merge parts, then retopo over it all.

Here’s good link to get you started on that:
http://www.zbrushcentral.com/showthread.php?t=44876

#5

@MagmaPixel: thanks for sharing that information!

chem!

#6

Good stuff, Magma, good tutorials!

#7

Thanks guys! I love Zbrush, and I remember how hard it was for me to really understand it at all. It’s thrilling to be able to help out a bit.

#8

Seriously - thank you! ZB doesn’t have the worst learning curve I’ve seen, but it’s certainly something you have to work to wrap your head around. You’ve been a really big help.

#9

thanks for the detailled and comprehensive response to this Qs…its helped me also. :beer:

#10

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