The drawing surface
The canvas as a parametric surface — flat, cylinder, sphere or cone — and the panels that bend and place it.
Reference
- Panel
- Surface
- Menu
- Window ▸ Panels ▸ Surface
Every layer draws onto a drawing surface: a parametric sheet placed in the scene, which the pen's coordinates are mapped onto. A flat plane is the default and the most common case, but it is one case among several. The same sheet can be bent into a cylinder, wrapped into a sphere, or tapered into a cone, and a stroke drawn on it lands on that geometry — not on a flat image that is afterwards projected.
The surface is a tool, not a container. It is the shape the pen is currently drawing onto, and it can be changed as often as the work requires, because each stroke keeps the shape it was drawn on. This is the single rule the rest of the page rests on.
Curvature is frozen per stroke
Every stroke carries a snapshot of the surface it was baked onto, and renders on that snapshot forever. Changing the grid's shape, bend, or placement affects only new strokes. One layer can therefore hold strokes of many curvatures at once — a flat background, a cylinder-wrapped band, and a sphere-wrapped cap — and re-bending the grid to draw the next element never disturbs anything already drawn.
Shapes
The Surface panel exposes four shapes.
| Shape | Geometry |
|---|---|
| Flat | A plane. The pen's coordinates are the surface's coordinates. |
| Cyl | A cylinder: the grid's horizontal axis bends around an axis, at the radius the Bend control sets. |
| Sph | A sphere: the grid wraps radially outward from its centre. |
| Cone | A cylinder whose radius varies along the grid's vertical axis, so the bend tightens along the sheet. The taper factor has no control in the panel. |
Two further shapes exist but are not offered here. An ellipsoid — a sphere with independent radii per axis, for skulls, torsos and blobby heads — and a capsule — a tube with a straight middle and hemispherical caps, for torsos and limbs. Both are created by Sculpt 3D's Create shape button, as Head and Capsule.
Inward and outward
There is no inward/outward switch. The Bend control is bipolar and its sign selects the direction: one side of zero bends the sheet toward the viewer, the other away. Zero is flat regardless of the shape selected.
The sign has a consequence in sculpting. A surface's outward direction is always the one leading away from its centre of curvature, so positive relief raises away from the centre of the form and negative relief carves in — on every shape, at every bend, whichever way you bent it.
Arc length
The shapes preserve arc length wherever the geometry allows it.
Flat, cylinder and cone are developable: they can be unrolled to a plane without stretching, so a line drawn on them keeps its length. A 200-point stroke laid around a cylinder is 200 points of ink around that cylinder, not 200 points of a flattened projection. The same holds for the cone across its taper, and for the capsule along its length across the seam between body and cap.
A sphere is not developable. No mapping from a sheet to a sphere can preserve every distance, and this one preserves distance radially from the grid's centre while distorting azimuthally — a deliberate, fisheye-like canvas rather than an accident.
The Surface panel
Reference
- Panel
- Surface
- Menu
- Window ▸ Panels ▸ Surface
The Surface panel bends the active layer's drawing surface and places it in depth. It ships docked on the right, as the selected tab of a pair it shares with Grid Transform, and can be reopened from the Window menu's Panels submenu.
Places the surface along the view axis — the z coordinate of the surface's origin. The scale is logarithmic and signed, so the fine placement near zero, where most work happens, gets the travel it needs while the extremes stay reachable. The Grid Transform panel's Pos Z field addresses the same value.
Flat · Cyl · Sph · Cone.
The signed curvature of the surface, in inverse points — the reciprocal of the bend radius. The scale is logarithmic and signed, and its limit corresponds to a minimum bend radius of 40 points. Disabled while the shape is Flat. Once bent, the label reports the radius it has reached, reading Bend · radius n rather than the neutral label.
The Grid Transform panel
Reference
- Panel
- Grid Transform
- Menu
- Window ▸ Panels ▸ Grid Transform
Grid Transform moves and rotates the drawing grid numerically — the text counterpart to dragging the gizmo. It is the second tab of the Surface panel's dock group.
The panel is a grid of text fields, three columns by two rows. The columns are the axes, labelled and coloured X in red, Y in green and Z in blue. Values are typed freely — there is no slider and no imposed range — and are shown to one decimal place, over a placeholder of 0.
The position of the grid's origin, per axis. The Z field is the same value as the Surface panel's Depth control.
The rotation of the grid, per axis, in degrees. Typing into one axis rewrites only that component and preserves the other two.
The panel has no scale row.
Moving or rotating the grid does not warp the art already on it: a whole-layer move carries the existing strokes rigidly with the grid, so the drawing travels intact rather than being remapped onto the new placement.