Repeaters

Automagic clone generation. a parent SO with a repeater config produces copies of its first child (the template) along a chosen axis. studs, joists, stairs, and ramps are all the same mechanism — what varies is the template shape, parent rotation, and constraints.

Files

• src/lib/ts/render/Engine.ts — sync_repeater(), the core engine logic
• src/lib/svelte/details/P_Repeat.svelte — repeater controls UI
• src/lib/ts/render/R_Dimensions.ts — fireblock dimensional rendering

Data model

The repeater field on Smart_Object:

Field	Type	Purpose
run_axis	0 | 1	which axis clones march along (never 2)
gap_min / gap_max	number?	constrained spacing range in mm (stairs)
spacing	number?	discrete spacing in mm (studs: 304.8 / 406.4 / 609.6 for 12/16/24")
firewall	boolean?	add horizontal fire blocks between clones
is_diagonal	boolean?	UI-only flag for straight vs diagonal button state
is_repeating	boolean?	true when actively repeating

Clones are never serialized. only the parent (with repeater config) and the template (first child) are saved. on load, propagate_all() triggers sync_repeater on every repeater, regenerating all clones.

Engine: sync_repeater

The workhorse. called after any propagation that touches a repeater SO.

Count resolution

• gap constraints (stairs): resolve_gap(gap_length, gap_min, gap_max) — finds count where total / count falls within [min, max], prefers even division
• spacing (studs): count = floor((parent_length - template_dim) / spacing)
• bookend: if the envelope extends past the last clone, a bookend clone is placed at the end. if the remaining space is less than the template thickness but more than zero, the last regular clone is shoved back to make room (tight bookend), and the fireblock between them shrinks to fit

Clone placement

Each clone gets an offset along the repeat axis: step * (i + 1) from the template position. bookend clones use bookend_offset instead. shoved clones use shoved_offset.

Diagonal (stairs)

When gap_axis !== repeat_axis, the engine offsets clones along two axes simultaneously:

• step along the run axis (distributes treads horizontally)
• gap_step along the gap axis (distributes treads vertically)

the staircase is emergent — the engine doesn't know about "stairs." it just sees that the gap constraint axis differs from the repeat axis.

Fireblocks

Horizontal members inserted between clones at mid-height. sized to the bay gap (distance between adjacent clone faces). the last bay may be shorter if there's a tight bookend — its fireblock is sized accordingly.

Display

P_Repeat.svelte shows:

• clone count (natural counting — includes the template, so 7 identical studs = "7 repeats")
• fireblock count
• straight/diagonal mode buttons
• spacing slider (studs: sticky at 12, 16, 24 inches)
• rise range dual-thumb slider (stairs: gap_min / gap_max)
• axis toggle (x / y)

Dimensionals integration

Repeater clones skip dimensionals to avoid visual clutter. exceptions:

• template (first child): gets all axes, like any normal SO
• first fireblock: gets repeat-axis dimensional only (so you can see the bay spacing)
• last fireblock: gets repeat-axis dimensional only if it's shortened (different length than the first fireblock, indicating a tight bookend bay)

Fireblocks are identified by comparing their repeat-axis length to the template's — they differ because fireblocks span the bay, not the stud width.

Use cases

Thing	Template	Parent rotation	Constraint
Stairs	step (wide, shallow)	atan(h/l) on repeat_axis	gap_min/gap_max (rise range)
Studs	stud (tall, narrow)	none	spacing (12/16/24 OC)
Floor joists	joist (long, shallow)	none	spacing (12/16/24 OC)
Roof joists	joist (long, shallow)	pitch angle	spacing (12/16/24 OC)