Overview

This project is a Blender addon that exports Blender meshes to Archicad library parts (.gsm).

This allows fully contained objects with textures and preview embbed. An optionnal LOD system (depecated because of library maintenance complexity)

The export pipeline produces:

• a 3D GDL script generated from the Blender mesh,
• a 2D GDL symbol generated from the object top view,
• an Archicad XML descriptor containing scripts, parameters, materials, textures, and metadata,
• optionally an LOD wrapper object that switches between detailed and simplified variants.

The XML output is compiled into .gsm files by LP_XMLConverter.exe, which is installed with Archicad and configured in the addon preferences.

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1. Repository Structure

ArchicadUtilitiesTest/
├── __init__.py                  # Addon entry point, preferences, version codes
├── operators.py                 # All Blender operators (the export pipeline)
├── mesh_to_gdl.py               # 3D GDL script generator
├── mesh_to_symbol.py            # 2D symbol generator (WIP, BVH approach)
├── xml_template.py              # Single-object Archicad XML builder
├── xml_lod.py                   # LOD wrapper XML builder
├── properties.py                # Blender property groups (UI data model)
├── interface.py                 # Blender UI panels (4 panels in the N-panel sidebar)
├── utils.py                     # String sanitisation helpers
├── local_dict.py                # GDL reserved keyword list (used by utils.cleanString)
└── standalone_scripts/
    ├── 3D optimiser.py          # GDL text-file TEVE/EDGE deduplicator
    ├── Replace line type.py     # Batch edge status replacer
    ├── poly2 to 3.py            # poly2_b{5} → poly_ command converter
    ├── compile_textures_to_objects.py  # Embed surfaces into object XMLs
    ├── mesh_to_symbol.py        # OLD 2D symbol generator (Freestyle SVG — superseded by mesh_to_symbol_new.py)
    └── Tiff_to_xyz.py           # GeoTIFF → XYZ terrain point cloud

Main addon files

• __init__.py — addon metadata, preferences, registration wiring
• interface.py — Blender UI panels shown in the 3D View sidebar
• operators.py — cleanup/export operators and the main export pipeline
• properties.py — scene properties, parameter model, default parameter maintenance
• mesh_to_gdl.py — 3D GDL generator from Blender mesh data
• mesh_to_symbol.py — 2D symbol generator from processed top-view geometry
• xml_template.py — XML builder for a normal exported object
• xml_lod.py — XML builder for the LOD wrapper object
• utils.py — identifier sanitization helpers
• local_dict.py — GDL reserved keyword list used by utils.py

3D optimiser.py

Purpose: Text-file predecessor to the TEVE/EDGE class logic in mesh_to_gdl.py. Reads a GDL .txt file, deduplicates TEVE vertices and EDGE entries using O(n²) nested loops, then writes a cleaned version. Functionally equivalent to mesh_to_gdl.py's dedup logic but operates on GDL rather than Blender mesh data. Note: Using soft edges (status=2 on EDGE) makes objects invisible in Archicad's sketch rendering mode.

poly2 to 3.py

Purpose: Converts Archicad 2D GDL script to 3D shape. Convert poly2_b{5} 2D GDL commands to poly_ format.

compile_textures_to_objects.py

Purpose: Embed Archicad surface definitions (materials + textures) directly into object XML files, making objects self-contained and portable across projects.

• For each Material parameter in an object, embeds the full DEFINE MATERIAL/DEFINE TEXTURE GDL block into Script_1D and copies texture files as GDLPict entries.
• Adds a GDL override block in Script_3D so users can still replace the embedded surface inside Archicad.

Tiff_to_xyz.py

Purpose: Convert a GeoTIFF heightmap to an XYZ point cloud for Archicad terrain import. Uses edge detection (Gaussian blur diff) to output high-detail points at terrain feature edges, plus a sparse grid for base coverage. Hardcoded input/output paths.

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2. Export Pipeline

(Optional) User clicks "Apply all" in Blender
        │
        ▼
ACACCF_OT_apply (operators.py)
  - Apply modifiers
  - Join all selected objects into one mesh
  - Optionally bake a coarse LOD variant (SubSurf level=0)
        │
        ▼
User clicks "Export" in Blender
        │
        ▼
ACACCF_OT_export (operators.py) — 7 steps:
  1. Triangulate mesh
  2. mesh_to_gdl.run_script()        → GDL 3D script string
  3. mesh_to_symbol.run_script()     → GDL 2D symbol string
  4. xml_template.run_script()       → Archicad XML string
  5. Write .xml + texture folder to disk
  6. Call LP_XMLConverter.exe        → converts XML to .gsm
  7. If LOD: xml_lod.run_script()    → LOD wrapper XML → LP_XMLConverter.exe

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Technical workflow

3. GDL Geometry Generation (mesh_to_gdl.py, mesh_to_symbol.py)

The core of the addon. Converts a Blender triangulated mesh into Archicad GDL 2D and 3D geometry commands.

Key GDL commands produced: | Command | Description | |---------|-------------| | TEVE x, y, z, u, v | Texture vertex (position + UV) | | EDGE v1, v2, f1, f2, status | Directed edge between two vertices | | PGON n, vect, status, e1, e2, e3 | Triangle polygon referencing 3 edges | | BODY -1 / BODY 0 | End of mesh body | | DEFINE MATERIAL | Material definition | | DEFINE TEXTURE | Texture definition |

Deduplication strategy (O(1)):

• TEVE: keyed by (x, y, z, u, v) tuple in a dict. Returns existing index on collision.
• EDGE: keyed by (v1, v2). Reversed edges (v2, v1) return a negative index (Archicad GDL mirror convention).

Per-material BODY loop: One BODY group is emitted per material slot, so Archicad can apply different building material to different parts of the mesh.

Surface override pattern: For each material, the GDL checks a user parameter:

IF sf_<name> = 0 THEN
    SET MATERIAL "material_<name>"
ELSE
    SET MATERIAL sf_<name>
ENDIF

This lets the user override surfaces inside Archicad without re-exporting.

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4. 2D Symbol Generation (mesh_to_symbol.py)

Uses BVH to generate a top-view silhouette:

1. Cast rays downward from a grid of points above the object.
2. Collect hit faces — these are the visible faces in plan view.
3. Merge coplanar faces, dissolve near-collinear edges.
4. Filter faces by restrictive visibility (remove faces fully occluded by others).
5. TODO: Convert resulting mesh to GDL POLY2 / POLY2_B commands. (Not implemented.)

The function run_script(start_obj) currently returns None.

Old approach (_old_mesh_to_symbol.py, superseded): Used Blender's Freestyle SVG renderer to render silhouette lines, then imported the SVG back as curves and converted to GDL. This implementation did return a GDL string. It was replaced but the operator call was not updated (see Bug #1 below). TODO: allow user to choose between new, old, and archicad's 2D generation (project2 command)

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5. XML / GSM Output (xml_template.py, xml_lod.py)

xml_template.py produces the Archicad XML format consumed by LP_XMLConverter.exe. Key sections:

• ParamSection: parameter definitions (type, flags, default value)
• Script_1D: property script (runs on library load; DEFINE MATERIAL, DEFINE TEXTURE)
• Script_3D: geometry script (GDL from mesh_to_gdl)
• Script_2D: 2D symbol script (GDL from mesh_to_symbol)
• GDLPict: embedded texture binary references

LOD wrapper (xml_lod.py): Creates a third .gsm that delegates to the LOD0 or LOD1 variant based on a macro_choose parameter, using a macro[] array: macro[1] and macro[2] = LOD1 (coarse), macro[3] = LOD0 (detailed).

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Planned Features

• Handle parametric GDL shapes from geometry nodes
• Handle modifiers as GDL code
• Support other object types: lights, doors, windows
• Auto-generate optimised 2D symbol (the current mesh_to_symbol_new.py is the WIP towards this)
• Self-shadow rendering for plan visualisation (ambient-occlusion-style, vectorial)
• Account for metadata (price, product reference)
• Mac support
• Version updater for objects created with older addon versions
• Let user choose between 2D generation method (Archicad's Project2, bitmap projection, geometric resolve)
• Add UI to use standalone scripts inside blender