Hello, welcome to ZBC!
First, to jump straight to a (hopeful) solution without having to read a wall of text:
- First, press Ctrl+N to clear the document of any pixels that have been painted on. You’ll see the image of your model dissappear but don’t worry, it was only an image (which is why you couldn’t sculpt on it).
- Next, on the Tool palette towards the right side of the screen, there is a slider just above the thumbnails. In the screenshot you posted, it currently reads “AlphaBrush. 1”. Grab that slider and move it all the way to the right to see the very last Tool saved in your project file. Hopefully it will be the head you were sculpting.
- If it is, then you can draw it back onto the document and re-enter edit mode to continue sculpting. If its nowhere to be found in the list then unfortunately it was lost and you’ll need to begin again.
Now for the long winded part: an explanation for how Zbrush works at its most core level. This is the first hurdle users will struggle with when they’re new to zbrush, but once it finally clicks the program will make a ton of sense.
Intro to Zbrush
The Zbrush interface is based around 2d painting software. Think of it as a painting program first and foremost.
The Document is an image document, no different than a Photoshop document (it can even export as a .psd file format). It is made up of pixels and has a width and height which you can set. The document even has layers, but they’re extremely limited in nature compared to something like Photoshop’s (for example, zbrush layers lack blend modes and opacity values). As a result, it is probably even easier to compare Zbrush to MSPaint.
The idea in zbrush is similar enough to any painting program: you grab a Tool from the Tool Palette (such as a PaintBrush), select a color from the Color Palette and adjust whatever Draw settings you want for that Tool (such as RGB intensity for the color, or brush size and shape), and then begin to draw the tool onto the Document to modify the document’s pixel values.
What sets Zbrush apart from something like MSPaint is three main gimmicks:
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Every pixel on the Document stores 5 channels of information. These include the standard Red/Green/Blue color values, but also a basic Z-depth and a Material name. The powers that be decided this was enough of an upgrade over basic pixels that they should call them “pixols”, hence their entire brand (Pixologic Zbrush = Using Pixols to paint with depth).
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Whenever you draw anything onto the document (lets say you’re writing your username with the paintbrush), the most recent stroke will remain in a temporary waiting state before actually dropping down to become pixel/pixol data. This gives you a chance to make a basic adjustment (move, scale, or rotate) to that most recent stroke. As soon as you lift your pen and begin making a new stroke to draw the next letter in your name, then that will become the most recent drawing (which means it will enter the temporary waiting state, and in the process will bump the previous drawing out into the document properly for it to exist solely as pixel data). It is important to know that even a quick, empty click on the document is enough to register the click as a new drawing, placing it inside the waiting state and bumping anything else out!
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You’re not just limited to your standard Painting Tools like the Paintbrush or Clone Stamp. Zbrush will let you use 3d models (Primitives or imported Polymesh objects) since they are naturally perfect Tools for sampling depth information from. When a drawing of a 3d Tool resides in the temporary waiting state then a fourth option opens up in addition to the previous Move/Translate/Rotate options. This fourth option is Edit Mode. With Edit mode turned on you can more freely position the 3d Tool where ever you want on the document, and even begin editing the vertex data of the Tool itself (so color and shape of the model) using a new set of brushes that work exclusively on the Tool as opposed to the Document. When you exit Edit mode and do something to bump the 3d Tool down to the document (which again can be as simple as clicking on the document to place the latest click in the temporary waiting state), the pixols then take on the MRGBZ data, and the Tool itself goes back to the Tool palette in case you want to draw it out again. An example of this is having a model of a brick with 10 million vertices worth of detail sculpted into it. You could use this 3d Tool to create a seamless pattern of 100 tiling bricks on your Document, and your computer wouldn’t struggle at all with this perceived detail because ultimately it is just creating a basic image rather than have a billion vertices worth of 3d models actively sitting on the screen.
And that’s zbrush in a nutshell.
I’m not sure if it was intended or not, but it just so happened that because Zbrush was using models in this specific way, it could ignore a lot of the additional complex data that 3d programs need to continually deal with (shaders, scene management, etc). Edit mode became a powerful way to quickly manipulate millions of vertices at a time with no slowdown back when such numbers would have been unthinkable in other programs, and you didn’t even need a fancy GPU either. So zbrush took off, and just about every one started to use Zbrush more for this specific Edit Mode in order to sculpt detailed models rather than to paint images. But even still, zbrush’s origins as a 2d program remains the backbone of what it is and how it operates.
So with this in mind, you should better understand the problem you ran into. When the program crashed, the drawing of the 3d Tool was bumped out of the waiting state, leaving you with just the image of it that was bumped onto the Document (pixels/pixols only). Since you don’t care about painting pixols and only want to sculpt, you must clear these pixols off with Ctrl+N, find your 3d Tool in the palette, draw it back onto the document to place it back in the temporary waiting state, and then re-enter edit mode when you’ve done so.
In time other little quirks from this approach should begin to make more sense as well, such as how you’re really manipulating a floating model rather than moving a camera around it. How its materials are all faked through screenspace / sphere referencing, why only one Tool can be active at a time, why all the short cuts favor a stylus over a mouse, etc. It all stems from the above.
Be sure to save your Tool often to (don’t save the document, that’ll just be an image file which isn’t what you want or need). Project files should contain every tool you’ve used along with the Document and several other settings, but these files can easily begin to balloon in size.