Sculpt 3D models with virtual clay

Get your hands digitally dirty with Sculptris and Alex Cox.

There are plenty of ways to be creative in the 3D realm, but few of them emphasise the creativity part of the equation as well as Sculptris does. Made by developer Pixologic — the company behind high-end 3D modeler Zbrush — it is, as its name suggests, primarily focused on sculpting. You’re given a big ball of digital clay, then you can poke, prod and pull it into just about any shape you like. Obviously, being based on a malleable, tangible material, Sculptris is best used to create organic shapes and creations; slashing out the slick lines of a high-end sports car is going to be rather difficult.

It’s not flawless, either. There will be times when you push your clay outside the realms of normal threedimensional physics. You might create so many polygons that your PC grinds to a halt — a decent amount of RAM and a capable graphics card is definitely recommended. But careful application of its tools and liberal use of the undo shortcut should be all you need to create something very cool indeed.

GET STARTED

Your first few steps in Sculptris really couldn’t be much simpler. Find the installer at pixologic.com/sculptris and download it. You’re asked to give up a bit of personal info to get the link, but you don’t explicitly have to — the link isn’t sent to your email, so lie if you must. Install it, run the software and you hit the interface. Tools at the top left, settings for the current tool running along the top of the window, and a big ball of gray clay slap bang in the middle, ready to be molded by your mouse, with a line of symmetry running down its centre. Give that clay a click right now. The default tool, and one you’ll come back to again and again, is ‘draw’, an additive tool that essentially dollops a little more clay on top of whatever you’re working on — the area you clicked, highlighted by the orange circle, should grow a little. Hold down Alt and you invert the draw tool, and scoop away clay instead; this switch between additive and subtractive modes is true of just about every tool in Sculptris’s palette, with a couple exceptions.

CAREFUL DOES IT

You may have noticed that the draw tool is a little trigger happy at this point. Using it leads to you adding or removing gigantic handfuls of clay, rather than performing the intricate molding you might be expecting. This is actually fine, because a real clay sculpture is generally made by lumping balls of material together, then smoothing them down later on. So use it, sparingly, to rough out the vague shape of the thing you’re trying to create. There are only 11 undo levels stored, so be careful; you’ll want to use small strokes rather than just holding the left mouse button and scribbling, but give yourself enough breathing room to take back mistakes. You can rotate your model by holding the right mouse button and dragging, pan by doing the same thing with Alt held, or zoom with the mouse wheel.

TWEAK THE TOOLS

This brings us to a curious feature of Sculptris’ interface. Although zooming brings your model closer in view, your tool remains the same size, meaning that you can now add finer details. This is certainly one way to get intricate, but you need to use the sliders for more pinpoint control. Size, as you might expect, alters the radius of the circle of influence, again maintaining the relative size from your viewpoint, even as you zoom, while strength tweaks the amount that the tool affects your model. We generally recommend using lowerstrength values where possible — the gentler you are, the less likely it is that Sculptris will place a stray vertex somewhere it shouldn’t be, and cause you problems down the line. Hit Space to bring a quick slider control up close to your cursor.

SMOOTHE IT OUT

You’ve added lumps, and by now you’ll have created a rather rough outline of the object you’re trying to create. You can now use two tools to refine your broad shape into something more workable — smoothe and flatten. The former is accessible no matter what tool you have selected. Simply hold Shift to quickly switch to it (or awkwardly select it from the tools panel, though this is a much less

efficient way of quickly prototyping your mould), then click and drag over your model to even out any rough edges. Again, this benefits from a lower strength, which you can set independently from the strength of your current tool, and it’s worth noting that you can’t invert the smoothe tool with Alt to make things rougher, because that would be silly. Flatten is a slightly more extreme tool, and one you’ll use less often — click a surface, and drag the circle over a higher or lower area to even things out to match the level of the surface on which you began your click.

CREASING UP

The crease tool, which we’ve used to add the cracks between the plates in our skull [ Image 1] is — despite our overenthusiastic use of it here — probably best left alone until the end of proceedings for two key reasons. One, it’s primarily a detail tool; two, it doesn’t play nice with smoothing. This means it’ll be the most prominent cause of vertex errors in your model, and once they’re there, they’re nigh on impossible to get rid of. If you must use it, pick a low strength and a large size, and crease gradually. The same goes for the pinch tool, which isn’t exactly a reverse crease — it behaves slightly differently, pulling your drawn bumps into more prominent ridges, but it’s still dangerous.

MASKING OFF

Sculptris’ rather vague, flamboyant circle of influence can be rather frustrating; editing one thing can lead to changes in other areas of your model. For our alien’s (rather frightening) teeth, we’ve avoided this by using a mask, highlighting the area we want to work on, and eliminating others. Before you go masking, though, it’s important to know that the mask brush does, by default, actually add polygons to your sculpture in order to cut off precisely the area you wish to work on. It doesn’t change its form at all, but it usually increases the overall complexity of your model. To prevent this, drag its detail slider to zero — now it’s restricted by the polygons you have already defined. The same is true for any of the tools we might use.

In our example [ Image 2], we’ve masked the whole head off, and left only the mouth region open for editing. You can do this by selecting the mask brush, holding down Ctrl, and clicking the background to invert the current mask. Because the whole model begins unmasked, the entire thing now becomes masked. Now, hold down Alt while drawing with the mask brush to invert it, essentially unmasking the bits you want to work on. You don’t need to go this extreme, though; unless you foresee your cursor flying all over the place, a simple ring around an object you’d like to edit, or a mask over