CURVE mode¶
Press 5 (or Tab from PATCH — it toggles between the two). CURVE is where
mesh density actually comes from, and where you split a patch into something
the fill can handle.
A curve is one boundary segment of a built patch — one CAD edge, fitted as a line or an arc. It is CAD truth: rigid, refit onto the surface. You do not move it, you decide how it is sampled, and the interior follows.
Built patches only
CURVE works on patches that really exist in the mesh. Fill first (PATCH), then tune.
Spans and contour¶
| Gesture | Effect |
|---|---|
| LMB / Shift+LMB / Ctrl+LMB | select / add / remove curves |
| LMB drag | box-select curves (front-facing only — nothing hidden behind the shell) |
Shift+G |
select every curve like the hovered one |
| Shift+Wheel | span — segment count of the selected curves, ±1 |
| Ctrl+Wheel | contour — redistribute the samples, count unchanged |
| Alt+Wheel | core span — the interior tube between the two selected curves, ±1 (below) |
E |
type the spans — digits, Enter; every selected curve lands on that exact count |
F |
reset the selected curves (span + contour) back to computed |
Ctrl+C / Ctrl+V |
copy the span of the curve under the cursor / paste it onto the selected curves as an exact count |
Select Similar here matches by what a curve is: the same segment type,
open or closed alike, and the same length within a tolerance (F9 to widen
it). A closed ring's length stands in for its radius, so "all the rims of this
bore size" is one keystroke — and it works on OBJ imports too, no CAD oracle
needed. The result replaces the selection; accumulate with Shift+LMB.
That pairs with the wheel and E: Shift+G the run of same-size rims, then
one gesture tunes them all — the finer-grained sibling of the PATCH-mode
mass tweak.
The copy reads the hovered curve, so the selection stays the paste target.
One buffer per session, shared with the PATCH-mode U/V copy
(PATCH); nothing under the cursor
or an empty buffer → Blender's own Ctrl+C / Ctrl+V.
Span is the count. It propagates to every patch sharing that curve, and the weld between them is preserved — that is the point of tuning at the boundary rather than inside one patch.
Contour is the distribution: bunch samples where the curve bends, thin them where it runs flat. Orthogonal to span, so the two never fight.
CAD seams. The seam of a wrapped CAD surface (a cylinder wall, a revolved
band) appears as a curve once the patch is built; its first span notch fixes
its position and sets the axial rows. X on such a seam puts it back to
automatic — every seam of that patch together.
By default spans are not guessed from radius but from silhouette error: a
curve gets the count that holds its chord within an absolute tolerance of the
true arc. Small arcs stay cheap, large arcs stay round, and the result does not
change when the model's overall size does. The tolerance is the
SILHOUETTE_TOL setting, expressed in the CAD's own working units (0.05 by
default — 0.05 mm on a millimetre-authored model).
Ring anchor¶
A closed ring — a bore rim, a round hole — has no natural start point, so its sampling can begin anywhere, which shows up as a rotated vertex ring.
A— hover the ring, press: the anchor lands on the ring sample nearest the cursor.- Alt+
A— clear the anchor of the hovered ring, or all of them when hovering nothing.
Bridge exports carry no parametric seam for rings, so this is a manual call by design.
Region split¶
This is not a cut
C does not slice geometry like a modelling loop cut. It draws a region
curve: a new boundary that partitions the patch. Each region is then
classified and filled on its own and welded at the seam — so both sides can
come back different from what was there before, by design.
That is how a face with a cut-out or an awkward feature gets a sane result: not one heuristic covering everything, but a smaller, honest problem on each side. Expect "re-decide both sides", not "an edge loop appeared".
C arms the split. Hover a built patch and the chord previews live,
perpendicular to the mesh flow.
| While armed | Effect |
|---|---|
| LMB | commit it — and stay armed for the next one |
C |
toggle auto ⊥ chord ⇄ 2-point mode |
| Ctrl+Wheel | spin the auto chord off perpendicular |
| Shift+Wheel | span count of the next split |
| Ctrl (held) | snap the chord's end to the nearest boundary vertex (sticky) |
In 2-point mode each click snaps to the nearest boundary span vertex and the curve
runs strictly between them. A tube (a closed wall with two rims) takes no
split — its fill is a bridge that ignores cuts, and C says so instead of
storing a dead one.
X deletes a selected region curve. Only your own committed ones are
deletable — a CAD curve stays put and the operator says so.
Side roles and core span¶
When you want a quad highway through a patch instead of a graded fill, mark the sides:
| Panel button | Meaning |
|---|---|
| Flow | this side feeds the quad core verbatim |
| Relief | this side absorbs the transition |
| Clear | remove the role |
Two opposite Flow sides plus a core span route the patch to the quad-highway fill. Roles are per patch: the shared curve keeps its seam contract and the neighbour is unaffected.
Core span sets the patch's interior resolution directly. Select the two opposite curves you want to reduce, run it: both are marked Relief, the boundary is kept verbatim, and an N-span interior tube is joined to each selected curve through a transition band. The seam still welds at full boundary resolution — nothing is sub-split behind your back.
Alt+Wheel does the same from the wheel. The number reads on the pair as
core N next to the span labels: it starts at the pair's own span and only
goes down from there — the core reduces, it never grows past the sides, and at
the pair's span the patch simply fills plain again. The core belongs to that
pair: pick the other pair of the same patch, Clear the roles, or F-reset
one of its curves, and it starts over from the new pair's span.
Where the gesture cannot apply it says so — a coloured line in the HUD block on the left, not just the status bar: the selection must be two curves of one patch, and the two other sides (the caps the interior grid runs between) must carry equal spans — Shift+Wheel them equal first. That equality is a limit of the highway grid, kept on purpose.