Sculpt 3D

The Sculpt 3D tool raises and cuts form. Where Sculpt Stroke moves the points of marks you have drawn, Sculpt 3D deforms the ground those marks sit on — a displacement stored per point of a grid laid over the surface, with the surface rendering bent by it — or the geometry of a solid directly.

Because the result is still the layer's drawing surface, it remains paintable. Details go on with the ordinary paint pipeline — draw the eyes and mouth onto the head you sculpted, with the brush you would use anywhere else.

The goal is a head or a body you can build, paint and pose in an afternoon, not a modelling application. There is still no modelling from primitives, no retopology and no UV unwrapping — but the tool is not confined to a heightfield any more.

What the brushes work on#

The same seventeen brushes shape two different things, and the tool picks between them from what your drag lands on.

The brushes mean the same thing on both — Crease cuts a crease, Grab pulls, Scrape shaves — because both read one shared description of how each brush behaves. Only the magnitudes differ, because a displacement over a surface and a displacement of a body are measured in different units.

A drag that starts on a solid goes to the solid, even when the layer also carries relief.

A solid subdivides itself#

A solid's detail used to be capped by the triangles it was built with: a brush finer than one triangle had no geometry inside it and did nothing at all. It now refines itself where you are working when the brush gets fine relative to the local triangle size, so a small brush bites on a large form.

Refinement is local to the brush rather than applied to the whole body, and it splits triangles without moving any existing point, so it can never alter what you have already sculpted. It runs on every brush except Grab, Snake Hook and Layer, which measure from the shape as it stood when the drag began.

Starting a sculpt#

Relief needs a surface to live on. The New sculpt controls at the top of the Sculpt 3D section create one as a new layer, activate it, and switch to this tool.

Lifting a painted layer into relief#

A layer that already holds artwork does not need a new primitive — the drawing itself can be lifted out of its plane.

The field is also created the first time you sculpt such a layer. The button exists because waiting for the first touch is invisible — the brushes were hidden until a field existed, and there was nothing to touch with.

Photo → 3D relief#

An imported photograph can be lifted into relief automatically, by predicting its depth.

The result is an ordinary sculpt field, not a special kind of object, so every brush on this page works on it: the prediction is a starting point you then correct by hand. The clay shell is hidden beneath it, because the photograph already covers the whole field and grey clay would only show through on steep slopes as an artifact.

Until the active layer holds something sculptable — a surface, relief, or a solid — the section shows only the instruction "Pick a shape and tap Create, then drag on it to sculpt."

Brushes#

Seventeen brushes ship, grouped in the Sub Tool panel under four categories.

Build#

Draw#

Adds height along the visible surface normal, at a rate scaled by the local slope: full on flat ground, fading to almost nothing on a cliff face. It never pushes material sideways — sliding a wall along is Grab's job, and per-dab resampling here was found to churn a rubbed mound into rings. On flat ground Draw and Inflate deposit identically; they diverge only on slopes.

Draw Sharp#

Draw with the falloff forced to Sharp (t²), concentrating the deposit at the centre into a crisp ridge or cut line. It also lays dabs twice as densely as the other brushes, because a feature narrower than the brush breaks into scallops at normal spacing.

Clay#

Fits a plane to the region under the brush, targets a height a little above that plane, and moves the surface toward the target only from the building side — it never cuts past its own plane. The consequence is that hollows fill first and the region evens out as it gains material, where Draw adds wherever the brush lands. Its per-dab amount is 1.5× the base, and its strength has a floor of 0.35.

Layer#

Raises at 0.6× the base rate per dab but never past a ceiling of 3× the base amount above the field as it stood at drag start. It is the only build brush with a per-stroke thickness cap: overlapping dabs within one stroke cannot pile up, so a scribbled patch comes out at one even height. Set to Subtract it carves a trench of one fixed depth in the same way.

Blob#

Draw with the falloff forced to Sphere (domed) and the amount at 1.15× — fatter and rounder than Draw, for massing out forms quickly.

Inflate#

Adds height radially to the base primitive, not along the visible normal. On a sculpted wall this is the whole contrast with Draw: Inflate keeps pushing out from the underlying ball or capsule regardless of what has been built on top, while Draw follows the surface as it stands. Inflate is the tool's default brush.

A brush smaller than about two grid cells would otherwise fall between them and do nothing; in that case the deposit is splatted across the four cells around the brush centre so a tiny brush still bites.

Carve#

Deflate#

Inflate with the amount forced negative. It carves even when Direction is Add, and setting Direction to Subtract does not turn it into a build brush — its sign is fixed in the kernel.

Crease#

A composed brush: a sharp cut at half the brush radius, followed by a pinch gathering material from 80% of the radius at 0.25× strength. The narrowness is deliberate. A full-width sharp cut reads as a wide soft trough rather than a crease, and a strong per-dab pinch bunches the groove into scalloped lumps as the stroke travels. Like Draw Sharp it lays dabs twice as densely.

The default direction cuts a groove. Inverted, the same composition builds a pinched ridge.

Scrape#

Moves the surface toward the stroke's plane but skips any point already at or below it — it only ever cuts. Drag it across a lumpy form and the peaks shave off while the hollows are left exactly as they were.

Punch#

Pierces a hole clean through the shell. Heights are not touched at all: this is a cookie-cutter cut, not a funnel. Points are marked as pierced where the weight exceeds 0.3 under the Smooth falloff, which lands near 80% of the radius — a stable stencil edge rather than a gradient, and one that still respects 3D distance, so punching a wall does not pierce the whole column behind it.

A hole has consequences you can work with: the surface clips away the pierced fragments, painted tiles drop their triangles there, and the sculpt raycast passes straight through to the interior back wall — so you can reach in and sculpt the inside through the opening.

Setting Direction to Heal closes a hole again. Because rays pass through holes, a heal drag is handed a phantom unpierced copy of the surface to aim at, so the pen catches exactly where you point it rather than landing on the far wall.

Refine#

Smooth#

Blends each point toward the mean of a neighbourhood scaled to the brush — a box roughly a quarter of the brush radius across, never smaller than one cell. A fixed small neighbourhood was invisible on any feature wider than a couple of cells; scaling it is what makes Smooth work on a large form. It reads from the field as it stood before the dab, so the result does not depend on the order points are visited in.

Flatten#

The two-sided plane brush: peaks come down and hollows come up until the stroked region lies on one plane. Contrast Scrape (cuts only) and Fill (raises only).

Fill#

Raises only the hollows to the plane, skipping any point already at or above it. The exact mirror of Scrape.

Pinch#

Gathers existing relief toward the brush centre by resampling each point's height from a little further out, so material flows inward. Its strength is throttled to 0.6×. It is purely redistributive: it adds no material and needs relief to act on — on flat ground it does nothing.

Move#

Grab#

The material under the anchor — the point where the stroke started — travels with the pen's total drag. Every dab recomputes the result from the field as it stood at drag start, so nothing compounds and the direction stays live-controllable mid-drag: drag out, then back, and the form follows rather than accumulating.

The drag is split into a component along the surface, which slides material, and a component along the normal, which pulls it out or dents it in — that second component is what lets Grab work on a smooth ball, where there is nothing to slide. There is no drag-length clamp: the grabbed patch travels as far as you take it. A large radius reshapes the whole form; a small one tweaks a feature.

Snake Hook#

The same kernel, given the live surface and the per-dab increment instead of the drag-start surface and the total drag. That one difference is the whole contrast with Grab: effects compound along the stroke, so material keeps being re-grabbed and drawn out into a tendril. The influence rides the growing tip — the root freezes, the tip follows the pen.

When the pull leaves what the displacement grid can represent, the drag switches to a real swept tube, which is how S-curves and waves become possible at all — a height over a surface cannot fold back on itself. The tube tapers toward its end, its centreline is relaxed so pen kinks do not facet it, and at drag end it is baked as a volumetric stroke. It therefore transforms and animates with the layer, and can be bent afterwards with Sculpt Stroke.

Mask#

Paints a protected region that no other brush can touch, rendered darker on the surface. Protection accumulates over passes; a full-strength pass masks completely in one. The weight is tripled before use, so protection saturates out to about two-thirds of the brush and only the outer rim feathers — a fully soft mask left a wide skirt that looked protected but only half blocked the brush.

Every other brush's weight is scaled by one minus the mask; the Mask brush reads the unmasked weight, or a full mask could never be lifted. Direction ▸ Unmask erases protection.

How a stroke deposits#

Weight is measured over true 3D distance from the point the pen hit, not distance across the grid. A tall feature's tip, walls and base all share a small footprint on the grid, so a grid-distance falloff treated the entire column as under the brush and touching a spike's tip dragged the whole spike. With 3D falloff only geometry near the hit in space moves. On flat ground the two are identical.

The per-dab amount is strength × radius × 0.06, so a bigger brush deposits proportionally more per dab and the feel of a given strength is consistent across sizes. Direction ▸ Subtract flips its sign.

A stroke deposits by distance travelled, not by touch-event rate — otherwise a slow pen laid several times more material than a quick flick over the same path. Dabs are spaced at 25% of the brush radius (12% for Crease and Draw Sharp), with an absolute floor. Fast segments are interpolated so a flick stays continuous, and a jump of more than six radii — a seam crossing, or the raycast losing the surface — restarts the chain instead of spraying dabs across the whole field. Grab and Snake Hook bypass spacing entirely; they are driven by the drag itself.

Adaptive refinement#

The displacement grid subdivides itself where you need detail. When fewer than about three grid cells span the brush, the grid doubles its resolution, resampling smoothly so the existing shape is preserved exactly. Holes and mask carry through the refinement. The ceiling is 1025 cells per axis.

Two details make this behave like real detail-on-demand. The cell pitch is measured in 3D, so a steep wall — where one cell spans much more actual surface than one cell of flat ground — counts as coarser and refines sooner; and the pitch is scanned across the worst slope under the whole brush, not just at the dab centre, because dabs land on a tower's flat top while the walls that need resolution sit inside the footprint. The check runs on every dab, so a drag that steepens its own walls as it deposits keeps refining as it goes.

The rendered surface follows: a refined grid draws through a denser mesh so its detail is not collapsed onto a handful of rings.

Limits and repairs#

The carve floor. A carve deeper than the local radius would push the shell through its own centre of curvature and turn a ball inside out. Carved heights are therefore clamped at 98% of the local radial depth, per point — an ellipsoid's radius varies, and so does its floor. Flat surfaces have no inside and are exempt: carving them is unlimited.

The wrap seam. On a capsule or cylinder the surface closes on itself. A stamp whose brush crosses the grid's edge is twinned a full turn away, so a stroke across the seam deposits on both sides instead of stopping dead; after edits near an edge the two seam columns — the same line of surface — are averaged together so the render cannot crack apart there.

Undo. One stroke is one undo step: the whole drag collapses into a single before/after record of the touched region, holes and mask included. The sculpt stack holds 64 of them.

Shading#

Relief is shaded with a cavity term: each fragment compares its height against its neighbours' mean, darkening grooves and pits and lifting ridges. Without it a camera-facing carve or crease is nearly invisible under plain lighting — the reason negative brushes can feel as though they do nothing on a flat-on view. Beyond a certain steepness the term fades out and the true geometric normal takes over, so a wall reads as a wall rather than aliasing. Masked regions grey out.

Options#

Symmetry mirrors the drag as well as the position, so a symmetric Grab pulls both sides outward together rather than dragging both in the same direction.

Below the controls, the panel shows a one-line description of the brush in hand.

See also#