| name | geometry |
| description | Use this skill for creating and manipulating geometry using ALLPLAN's geometry engine (NemAll_Python_Geometry module). |
Overview
All geometry in ALLPLAN PythonParts is constructed using the NemAll_Python_Geometry module (aliased as AllplanGeo or AllplanGeometry):
import NemAll_Python_Geometry as AllplanGeo
Geometry objects are pure mathematical constructs — they define shapes in space but are not ALLPLAN model elements on their own. To place geometry into the model, wrap it in an AllplanElement (see the allplan-elements skill).
Core Principles
Units
- All coordinates and distances are in millimeters.
- All angles are in radians (use
AllplanGeo.Angle.FromDeg() for degrees).
2D / 3D Duality
Most geometry types exist in both 2D and 3D variants (Point2D/Point3D, Line2D/Line3D, etc.). They share similar APIs but live in different coordinate spaces. A 3D object can often be constructed from its 2D counterpart (Z defaults to 0).
Two Solid Representations
ALLPLAN supports two types of volumetric solids:
| Type | Class | Engine | Faces |
|---|
| Polyhedron | Polyhedron3D | ALLPLAN internal | Planar only |
| BRep | BRep3D | Parasolid | Curved (NURBS) |
Prefer polyhedrons for performance. Use BRep when curved surfaces are required. Do not mix them in boolean operations — convert first.
When a BRep3D constructs a ModelElement3D, the element type is BRep3D_Volume_TypeUUID.
When a Polyhedron3D is used, the type is Volume3D_TypeUUID.
Never switch between them when modifying existing elements.
Transformation via Matrices
All spatial transformations (translate, rotate, scale, reflect) are expressed as Matrix3D (or Matrix2D). Apply with multiplication:
geometry *= matrix
Matrices compose via multiplication (order matters — not commutative).
Error Handling Pattern
Many geometry functions return an (error_code, result) tuple. Always check the error code before using the result.
err, polyhedron = AllplanGeo.CreatePolyhedron(solid)
Geometry Object Categories
| Category | Examples | Characteristics |
|---|
| Primitives | Point2D/3D, Vector2D/3D, Angle | Building blocks, support arithmetic |
| Linear | Line, Arc, Polyline, Spline, Axis | Curves with length, no area |
| Areal | Polygon2D/3D, Plane3D | Closed/planar, have area |
| Volumetric | Polyhedron3D, BRep3D | Solids with volume |
How-To Articles
Load these on demand based on the task:
- Geometry objects — Constructing geometry primitives and curves (Point, Vector, Angle, Line, Arc, Polyline, Polygon, Spline, Axis, AxisPlacement, Plane)
- Basic solids — Creating basic 3D solids (cuboid, cylinder, cone, sphere) as Polyhedron or BRep
- Extrusion — Extruding profiles vertically or along a vector
- Sweep — Sweeping profiles along a path or rails
- Revolve & Loft — Creating solids by revolving or lofting profiles
- Build from Scratch — Building BRep or Polyhedron from scratch (BRep3DBuilder, Polyhedron3DBuilder)
- Boolean Operations — Union, subtraction, and intersection of solids
- Intersections — Calculating geometric intersections (curve-curve, curve-plane, solid-solid, solid-plane, ray-solid)
- Transformations — Translation, rotation, scaling, reflection, projection, and composing transformations
- Fillet & Offset — Fillet edges/lines and offset curves/faces
- Measurement — Length, area, volume calculation, center of gravity, comparison, and polyhedron validation/repair
- Hidden Calculation — Projecting 3D geometry to 2D lines (visible/hidden edges)
- Tessellation — Converting BRep to Polyhedron via tessellation
