Browser BIM 2D Guide¶

Architecture: 2D Layout | Theory: BIM Modeller OOTB | Manifesto: MANIFESTO.md

Getting Started¶

Open the viewer: load any building from the landing page
Press G to toggle the grid overlay
Click GF in the panel to see a floor plan with door arcs and dimensions
Long-press a grid line (~0.4s), drag it — the cost panel appears
Press Ctrl+Z to undo. Reload the page — grid stays where you dragged it.

Keyboard & Interaction Cheat Sheet¶

Key / Gesture	Action
G	Toggle grid overlay on/off
GF button	Ground Floor plan — section cut + door arcs + opening labels
L1 button	Level 1 plan
Front / Back / Left / Right	Elevation views
Roof	Roof plan view
Unlock (lock icon)	Return to free 3D orbit
Long-press (~0.4s) on grid line	Start grid drag — 3D planes appear
Drag after long-press	Move grid line — cost panel updates live
Release	Commit `GRID_MOVE` to `kernel_ops` log
Ctrl+Z	Undo last grid move
Ctrl+Shift+Z or Ctrl+Y	Redo undone grid move
Alt+Z	Toggle X-ray mode
F11	Toggle fullscreen
Scissors slider	Move cut plane — grids recompute at new elevation
Save cut	Save current section as named view
F5 / reload	Grid positions restored from log — no save button needed

Views and What They Show¶

Floor Plan (GF / L1)¶

Clicking GF or L1 locks the camera to a top-down orthographic view and fires a horizontal section cut through the building:

Wall contours — closed polylines from triangle mesh slicing at the cut elevation
Door swing arcs — quarter-circle arcs computed from door leaf bbox + nearest wall hinge
Window dashes — jamb tick marks at each window opening
Opening labels — width in mm (900W) + type tag (Single-Flush) above each door/window
Dim chains — bay widths between grid lines, total span per axis
Grid bubbles — labelled circles (1, 2, A, B) at line endpoints

The cut height is storey-aware: it finds the floor slab top and cuts 1.0 m above it (configurable in grid_rules.json → floor_plan.cut_offset_m).

Elevation (Front / Back / Left / Right)¶

Locks camera to face the building from that direction. Elevation contours project visible edges. Level markers show storey heights.

Scissors (Section Cut panel)¶

The slider moves a cut plane through the building on any axis (X, Y, Z). Grids recompute adaptively at the new elevation. This is a free-form exploration tool — door arcs and opening labels only appear in the named views (GF, L1), not in scissors mode.

Grid Drag and the Cost Panel¶

When you long-press and drag a grid line:

3D planes appear — semi-transparent red (X-axis) and blue (Y-axis) rectangles slicing through the building
The grid line moves, constrained by grid_rules.json (min bay width, snap quantum, max step)
On release, a GRID_MOVE operation is committed to the kernel_ops table in the building's SQLite DB
The cost panel appears (bottom-right) showing elements within the grid scope:
Grouped by IFC class (Wall, Column, Door, Window, Slab...)
Quantities, area (m2), volume (m3) per class
Click x to close the panel

The cost panel query:

SELECT ifc_class, COUNT(*), SUM(bbox_x * bbox_y), SUM(bbox_x * bbox_y * bbox_z)
FROM elements_meta JOIN element_transforms ON guid
WHERE center_x BETWEEN gridX1 AND gridX2
  AND center_y BETWEEN gridY1 AND gridY2
GROUP BY ifc_class

This is a spatial BOQ — the bill of quantities scoped to the area between grid lines.

Persistence — No Save Button¶

Every grid drag commits a GRID_MOVE row to the kernel_ops table in the building's SQLite DB. On page reload, the grid overlay replays all non-undone GRID_MOVE ops and repositions grid lines to where you left them.

Undo marks the op as undone=1 (soft delete, not hard delete — full audit trail preserved)
Redo clears the undone flag
The DB is the save. There is no save button because every operation is already saved.

See BIM Modeller OOTB — The Modelling Inversion for the architectural reasoning.

Configuration — grid_rules.json¶

All constants are externalized in grid_rules.json, never hardcoded:

Block	Controls
`grid_move`	`min_bay_m`, `max_extend_m`, `snap_m` (50mm default), `max_step_m`
`grid_detection`	`min_structural_span_m`, `face_cluster_tol_m`, `min_votes`, structural/opportunity classes
`floor_plan`	`cut_offset_m`, storey band filter, `opening_label_offset_m`, `opening_label_font_px`
`plane_3d`	`plane_opacity`, `plane_color_x` (red), `plane_color_y` (blue), `show_on_drag`
`clearance`	Per-class rules for cascade: `wall_min_m`, `grid_min_m`, strategy (proportional/pin_to_wall/center_bay)
`shadow`	Drag shadow colour and opacity

Known Limitations (Current Session)¶

Issue	Status	Next step
Grid alignment on complex buildings (SampleCastle, HITOS)	Grid lines don't always align with structural walls	Tune opportunity-vote weights; add snap-to-wall post-processing
Saved section restore	Section appears in panel but clicking it back doesn't restore view properly	Debug `restoreSavedSection()` path
2D convention parser	Scissors mode shows raw contours — no door arcs, no noise filtering	Apply 2D conventions (arcs, line weights, class filtering) to all section views, not just GF/L1
Drag result as new building	The cost panel shows what changed but doesn't save as a variant building	Future: `commitOp('VARIANT')` creates a fork of the building DB

Console Log Tags (Debugging)¶

Open browser console (F12) and look for §-tagged lines:

Tag	What it proves
`§KERNEL_OP committed id=N type=T`	Operation logged to DB
`§KERNEL_OP undo id=N`	Undo succeeded
`§KERNEL_OP replay moves=N`	Init replayed N saved ops
`§GRID_3D_PLANES count=N`	3D planes injected
`§GRID_3D_BOQ elements=N`	Cost panel refreshed
`§GRID_3D_BAND_VIS shown=N hidden=N`	Storey band visibility applied
`§DOOR_ARC_LABEL guid=G width=Nmm`	Opening label generated
`§GRID_DETECT xLines=N yLines=M`	Grid detection ran
`§GRID_UNDO attempt op=T`	Ctrl+Z fired