Repeating a Body Along a Line

Use a 3D pattern to repeat a whole solid: a row of feet under a base, a grid of bosses on a plate, a line of teeth on a rail. Select the body, pick Linear pattern (3D) or Rectangular pattern (3D), set a spacing and a count, and the copies appear along the direction you chose.

The tools only appear with a body selected

The four 3D pattern tools appear only when at least one body is selected. A face does not count, and neither does an edge. They are not greyed out and they do not tell you why: they are not on the toolbar at all.

Clicking a solid in the viewport gives you a face, which is exactly the selection that hides these tools. Two gestures give you a body instead:

• Double-click the solid in the viewport. Hold Ctrl or Shift while double-clicking to add more.
• Set the Select tool's filter to Select bodies, after which single clicks pick whole bodies.

If you went looking for a pattern tool and it was not there, you had a face selected. Nothing else is wrong.

What the defaults build

A linear pattern created on a body arrives ready to preview: spacing 10 mm, count 3, direction the X axis, with Symmetric off. A rectangular pattern arrives with both spacings at 10 mm, both counts at 3, Direction 1 on X and Direction 2 on Y.

The popover fills Sources from your selection, in pick order and with duplicates dropped. Its help line reads Click bodies in the viewport to pattern them., and that is literally how you change the list.

Direction is seeded from the first thing you had picked that can act as a direction: an edge, a reference axis or a world axis. Direction 2 of a rectangular pattern is never inferred. It stays on world Y without saying so, which is fine for a plate on the XY plane and wrong the moment your grid is not axis-aligned. Set it yourself.

The original stays put

The seed body is never re-emitted. It stays exactly where it is and the pattern lays count - 1 copies along the direction, so a count of 3 gives you the original plus two.

A rectangular pattern walks the whole grid and skips only the cell the seed occupies. Counts of 4 and 3 therefore produce 11 copies, not 12: count1 x count2 - 1. And the two legs are not required to be perpendicular, so a rhombic grid is a matter of picking two edges that meet at whatever angle you like.

Spacing, count and the fields that take expressions

Every numeric field takes a parameter or an expression, not only a typed number. A row of cooling fins whose count is fins and whose spacing is wall * 3 rebuilds correctly when either parameter moves, which is the whole reason to pattern rather than copy.

Negative spacing is worth knowing about, because there is no reverse toggle. If the copies ran the wrong way, put a minus sign in front of the number.

Spacing is measured from copy to copy, not between their surfaces, so the gap two neighbours leave is the spacing minus the body's own width along that direction. Close that gap below one bead width and the slicer welds them together: on a 0.4 mm nozzle, anything under about 0.4 mm of air comes off the printer as one wall, whatever the One body toggle says the document contains. Two parts you intend to snap apart want 0.4 mm at the very least, and 0.5 mm if the first layer squashes out.

The direction picker refusing faces catches people out. The face of a plate is not a direction. Pick one of its edges, or build a reference axis first; Reference Axes and Points covers how.

Symmetric

With Symmetric off, the copies run from the seed in one direction. With it on, they split around the seed instead.

The arithmetic is worth having straight before you type a number. An odd count comes out centred on the original: five copies at 10 mm put two on each side, with the seed in the middle. An even count cannot be centred on one body, so the seed ends up as one of the two central instances and the set is symmetric about the gap between them.

Reopening a pattern to change it

Every field stays live for the life of the document. Left-click the pattern's pill in the timeline and its popover opens with the sources, the direction, the counts and the spacings exactly as you left them. The pills are named Linear pattern 1 and Rectangular pattern 1 in creation order, which is how you find the right one.

One trap waits inside. Reopen the Sources picker on an existing pattern and it starts with nothing in it, not with the bodies already listed. The first body you click replaces the whole list rather than adding to it. If you meant to add a fourth source to three, click all four.

When it fails

Four of the five refusals are typing mistakes and read as such:

3D pattern requires at least one source feature

3D pattern count must be at least 2

3D pattern spacing must not be 0 mm

3D pattern axis could not be resolved

The last one is the interesting case. It means the edge or axis you chose as a direction is not there any more, because a step earlier in the timeline changed the geometry it came from. Reopen the pattern and pick the direction again.

One more refusal is about the sources rather than the numbers:

A source feature of this 3D pattern was deleted

Something you were repeating no longer exists. Edit the pattern and rebuild its Sources list.

See also

• Repeating a Body Around an Axis: circular patterns and the four different mirrors
• What a Pattern Produces: separate bodies or one fused solid, and what each exports as
• Working with Several Bodies: living with the bodies a pattern hands you
• Transform Basics: moving a single copy after the fact