MAGMA

Magma Rectilinear Pattern — Design Note (locked)

Second Magma infill pattern, after Triangle and before Tri-hex. This note is the implementation reference; the design below is settled.

Terminology: rectilinear (a.k.a. “square”) cells pair into the same U-tube as the triangle pattern — two adjacent cells joined by a window gap at their shared wall, injected down one and vented up the other. It is the degenerate 1-leg manifold, exactly like triangle; only the cell shape and line families differ.

1. Lattice — square grid

• Two perpendicular single-wall line families spaced cell_spacing apart, so each cell is a square of side = cell_spacing. No skew, no parity (unlike the triangle’s up/down cells).
• CellId uses (a, b) = integer (column, row); c and kind are unused (0). Each cell is the unit square [a, a+1] × [b, b+1] in lattice space.
• World mapping is a plain axis-aligned scale + spiral offset: to_world(lx, ly) = (lx·cs + off_x, ly·cs + off_y).
• RectilinearLattice::neighbors() returns the 4 edge-sharing neighbors (L/R/U/D); is_up() is always false; max_neighbors() = 4.

2. Cell geometry — SquareGeometry (MagmaGeometry impl)

Walls are single shared beads centred on the grid lines, so the open interior is inset by line_width/2 on each of the four sides → inset (open) square side = spacing − lw.

• edge_length = spacing (the line spacing IS the square’s side).
• inset_open_area = (spacing − lw)².
• opening_diameter = (spacing − lw)·√2 — the circumscribed circle of the inset square, which the nozzle flat must cover when sealing (all four corners).
• Seal ratio (opening / interior) = √2 ≈ 1.41, vs the triangle’s 2.0 — the square seals more easily, so a given seal depth buys a larger interior (interior_for_opening = opening / √2).
• neighbor_centroid_distance = spacing (orthogonal grid; simpler than the triangle’s side/√3).
• vertex_overlap_excess_area = lw² — only 2 line families crossing at 90°, ~1 crossing per cell (vs the triangle’s 3 families at 60° → 3√3·lw²/4). Less material is double-deposited, so less is subtracted from the injected volume.
• window_volume = (spacing − lw)·lw·window_height — the shared-wall gap.
• auto_window_height = (spacing − lw) = interior_width — written as area/edge to parallel the triangle, so the window flow cross-section equals the tube’s open cross-section.
• max_neighbors = 4; a pair is 2 cells.

3. Window placement — square_window_cuts (pattern-owned)

For each open U-tube pair (the solver decides which pairs are open on a given layer):

• cells differ in column (a) → the shared wall is vertical → cut the gap into vert[col] as a Y-interval;
• cells differ in row (b) → the shared wall is horizontal → cut into horiz[row] as an X-interval.

Intervals are merged per line index. Simpler than the triangle, which must classify the shared edge into three families (horizontal / 60° / 120°).

4. Toolpath — FillMagmaRectilinear::_fill_surface_single

• Two line families over the bbox-derived ranges (no skew):
  • horizontal (one per row b): y = b·cs + off_y, spanning X;
  • vertical (one per column a): x = a·cs + off_x, spanning Y.
• Window gaps interrupt the relevant family via subtract_gaps (Y-intervals split vertical lines, X-intervals split horizontal lines).
• Each family is clipped per line (so a line’s fragments stay adjacent for the sweep), then chain_or_connect_infill routes within the family. Anchoring is disabled (zone shells provide the bonding surface).

5. Solver / injection / preview — UNCHANGED

• The tube solver (greedy warm start + optional CP-SAT) is pattern-agnostic: a square cell with 4 candidate neighbours instead of the triangle’s 3 is just more edges; the matching, runs, segments, stagger, and CP-SAT model are identical.
• Per-layer presence scan, injection G-code, seal/plunge/crater-iron, the spread-heat injection ordering, and the preview tube viz are all shared and unchanged.
• Spiral interlock applies (the square lattice translates per layer like the triangle).

6. New vs reused

• NEW: the square lattice (RectilinearLattice) + SquareGeometry; square_window_cuts; the 2-family axis-aligned toolpath.
• REUSED unchanged: the tube solver (greedy + CP-SAT), runs/segments/stagger/height bounds, presence scan, U-tube pairing, injection sequence, preview viz, dual-zone outer fill (any pattern may fill the outer zone).

This site is open source. Improve this page.