Overview
- Basic 3D Concepts
- Geometry
- Primary and secondary levels of detail
- Choosing appropriate tool and subdivision level
- Process
- Recognizing poor topology (Stretching)
- Converting a PolyMesh to a Dynamesh Surface
- Basic Facial Anatomy
- Resolution requirements
- How many subdivisions should I have?
- How many Polygons?
Basic 3D Concepts
PolyMesh
A polymesh is a 3D model that is composed of polygons. A polygon (sometimes called a face) is a shape that is enclosed by a number of points (sometimes called vertices) connected by edges.
Topology
The term "topology" also refers to an object's mesh and specifically addresses in which directions the edges flow and how the mesh has been pushed and pulled. Here, and object's mesh is displayed by going to Transform > PolyFrame or by using the PolyFrame (Shift+F) shortcut.
Edge Loop
This term "edge loop" comes up a lot in 3D modeling and sculpting. It is a series of connected edges that traverse a 3D object's surface and ends where the loop started. They are essential in creating things like hard edges and bevels on hard-surface objects as well as for deformations on organic objects. For the latter, it takes at least three edge loops to bend a finger at the middle knuckle, one to hold the knuckle in place, and two on either side of the knuckle to bend the finger.Tool -> Geometry
Lower Res The Lower Subdivision Resolution ("Lower Res") button is in the top left corner of the subpalette. This button switches your active ZTool to the next lower resolution mesh.
Hotkey: Shift + D
Higher Res Just to the right of the Lower Res button is the Higher Resolution Subdivision ("Higher Res"). Clicking this button steps up your active ZTool to the next higher resolution mesh. To add more subdivision levels, you can press the Divide button (see explanation of "Divide" button below)
Hotkey: D
SDiv Slider
Immediately beneath the Lower Res button is the SDiv slider, which allows you to lower or raise resolution mesh subdivision levels.
Del Lower Beneath the SDiv slider is the Del Lower button. This removes all lower resolution meshes from the active ZTool. Note that it's a common mistake for users to click this button when all they want is to step through subdivision levels. In that case, use SDiv Slider or the Lower Res or Higher Res options.
Del Higher This button is located to the right of the Del Lower button. It removes all higher subdivisions from the active ZTool. As with the Del Lower button, you'll not want to use this button when you are looking to just step through resolution-mesh subdivision levels.
Divide Pressing Divide will divide each polygon on your object twice—once horizontally and once vertically—thus resulting in four times the number of polygons. Use this button when you are sculpting and need additional resolution.
Make sure any masks are cleared before pressing the Divide button; otherwise ZBrush will divide only the unmasked polygons. This can lead to problems later on in the sculpting process and be difficult to fix. As a reminder, to clear your mask, hold the CTRL key and drag a small rectangle outside of your mesh on the blank canvas.
Focus on Primary and Secondary Forms!
From left to right, this image represents primary and secondary forms with tertiary details on the right.
It's a common habit of beginner sculptors to start working on tertiary details too early in the process. This can lead to unfortunate results, because when it comes to creating a successful design or sculpture, easy-to-read, crafting beautiful primary and secondary forms is most important.
Process
"The [human] figure, when rendered in clearly conceived masses, regardless of the amount of detail presented, produces a powerful artistic statement." - Eliot Goldfinger, Human Anatomy for Artists: The Elements of Form
Converting PolyMesh to DynaMesh
Here's how you convert your 3D object from a PolyMesh to a DynaMesh surface once you've determined that it's the right thing to do.
Set your subdivision level
- You'll want to choose a level that's high enough to capture any details you don't want to lose. This likely will be the highest level.
- Tool > Geometry > SDiv
- Delete lower and higher subdivision levels (if any exist). Your Geometry subpalette should look something like this, with the SDiv slider grayed out.
- Convert to DynaMesh
- Tool > Geometry > DynaMesh > DynaMesh
- Check resolution
- Tumble around your model to check that you didn't lose any wanted details.
- Adjust resolution if necessary
- If you have too much resolution, Undo, turn down Resolution, re-DynaMesh
- If you don't have enough resolution, Undo, turn up Resolution, re-DynaMesh
- Be careful not to turn the resolution up too high. Only increase it as needed. It's common to increase the resolution by doubling the value. So a typical sequence would be 16, 32, 64, 128, etc.
When you convert to DynaMesh, you will lose the ability to step up and down in subdivision levels. Saving before converting and saving a new version right after converting is a good idea.
Basic Facial Anatomy
Here are some useful measurements to remember when sculpting a human head from a sphere. They are based on the "Divided Ball and Plane Method" developed by the legendary illustrator and art instructor Andrew Loomis:- The equator of the sphere marks the line of the brow.
- Just below the top of the cranium (approximately 1/6th of the overall head length down) is the hairline or the top of the face
- If you divide the face (from the hairline to the jaw) vertically in thirds, the browline and bottom of the nose sit on the first and second third (see above image)
- The eyes sit halfway between the top of the head and the jaw. They are set about one eyeball width apart and on average measure approximately just under an inch in diameter.
The ear sits just behind the halfway mark of the head and is angled back at the same angle as the jaw- The mouth line sits one third below the bottom of the nose and the chin.
Pro Tip:
Every good sculptor has a repository of anatomy references. Some may be physical (a cast skull and bones, busts, books) and some may be digital (images on a hard drive, a Pinterest board, or an iPad app). Most likely it will be a combination of many things. Start now to develop your own personal library of anatomy resources and tools.
Resolution Requirements
Here are a couple of common questions asked by ZBrush users:
How many subdivisions should my model have?
- Answer: Use only as many as you need. Do not add subdivisions until you cannot effectively sculpt at your current highest level.
How many polygons should my model have?
- Answer: As with subdivisions, you should only have as many as you need. When you want to execute finer, more precise details, it's not uncommon at the highest subdivision level to sculpt somewhere between 10-60 million polygons.
The answers to these questions will also depend on your computer's hardware limitations (or lack thereof if you're lucky!). With the 4r7 version, ZBrush supports 64-bit operating systems, which will greatly increase your processing power. You'll know you're approaching your limits when your files sizes start getting too large and your sculpting begins to lag or is sluggish.
To check your polygon count, hover your mouse over the active tool's thumbnail in the Tool menu. Here you will see Polys (number of polygons at your current subdivision level for your current subtool) and TotalPolys (number of polygons at your current subdivision level for all subtools).
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