Automatic ids

Every element drawn in a sketch gets an id made of its kind and a number, such as Line.1, Arc.2, Circle.1 or Spline.1, as in CAD sketchers. Every point gets an id like Point.3, and every chain drawn in one go an id like Chain.1. id= gives an element an id of your own instead.

Ids are the references within the sketch, and they never leave it. Faces, wires and exports carry only the names given with name=, which travel with the geometry through Boolean operations and into the mesh.

[1]:

import math
import planex as px

An L bracket drawn quickly

The example is an L bracket with legs 40 and 30 long and 10 thick, drawn without a single id= (Figure 1). Its six sides are therefore Line.1 to Line.6 in drawing order, and its corners Point.1 to Point.6, from the start at the origin. The re-entrant corner is Point.4.

[3]:

s = px.QuickSketch().Line(40).Turn(90).Line(10).Turn(90).Line(30)
s.Turn(-90).Line(20).Turn(90).Line(10).Close()
corner = s.Location("Point.4")
print("Point.1", s.Location("Point.1"), "Point.4", corner)

Point.1 (0.0, 0.0) Point.4 (10.0, 10.0)
An L bracket labeled with its automatic ids
Figure 1: An L bracket labeled with its automatic ids

Referring to them

Later calls refer to the automatic ids like to any other (Figure 2):

  • a bolt hole of 5 lies opposite the middle of Line.2, the end of the long leg, 8 in from it, and gets the name bolt for the export;

  • the washer around it is a construction circle, concentric with Circle.1, the automatic id of the hole;

  • a construction line from the re-entrant corner Point.4 to the outer corner Point.1 marks where a gusset would go.

[5]:

end = s.Location("Line.2.mid")
s.Circle(2.5, center=(end[0] - 8, end[1]), name="bolt")
s.Circle(5, concentric="Circle.1", construction=True)
s.Move("Point.4").Line("Point.1", id="gusset line", construction=True)
bracket = s.Face()
The hole Circle.1, its washer and the gusset line, by their ids
Figure 2: The hole Circle.1, its washer and the gusset line, by their ids

Only the name given with name= reaches the face, while the ids stay in the sketch:

[7]:

print("area", bracket.mass, "exact", 40 * 10 + 20 * 10 - math.pi * 2.5**2)
print({e.name for e in bracket.edges})

area 580.3650459150638 exact 580.3650459150638
{None, 'bolt'}

Ids are also how the editing calls find their elements. Fillet("Point.4", 5), for example, rounds the re-entrant corner by the id of its point. See Fillets and chamfers for details.