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Features

Features refine a part: rounding and beveling edges, hollowing, splitting, mirroring. Each one is a method of Part that returns a new part.

Fillets​

from smlibpy import *

box = Box(40, 30, 20)
rounded = box.fillet(box.edges().parallel_to(Z), 5)

Select the edges, give a radius. Edges can come from the part, from a face (box.faces().top() rounds all its edges) or from an earlier version of the same part: smlibpy matches them by position.

The free function fillet(edges, radius) finds the part the edges belong to, which reads well when the selection says it all:

rounded = fillet(box.edges().parallel_to(Z), 5)

Variable radius​

A (start, end) tuple changes the radius linearly along each edge:

ramp = box.fillet(box.edges().parallel_to(Z).first, (2, 8))

Different radii​

A list gives each edge its own radius:

edges = box.edges().parallel_to(Z)
stepped = box.fillet(edges, [2, 4, 6, 8])

Smooth blends (G2 and G3)​

A circular fillet meets its faces with matching tangents but a jump in curvature; on a glossy surface that shows as a highlight line. SMLib can blend with matching curvature (G2) or even matching rate of curvature change (G3), as used for consumer products and car bodies:

soft = box.fillet(box.edges(), 4, continuity="G2")
softer = box.fillet(box.edges(), 4, continuity="G3", fullness=1.2)

fullness shapes the blend's cross-section: above 1 is fuller, below 1 flatter.

What can't be rounded​

Seam edges (where a cylinder closes on itself) and edges between faces that already meet smoothly are skipped automatically. A radius that cannot fit raises a ModelingError that says how much room there is:

cube = Box(10, 10, 10)
try:
    cube.fillet(cube.edges(), 6)
except ModelingError as e:
    print(e)   # ... the rounds on edges 10 apart would overlap (largest possible setback here: 5)

Fillet order matters where rounds meet. Where three rounded edges meet at a corner, round the larger radii first.

Chamfers​

beveled = box.chamfer(box.faces().top().edges(), 2)

length is the setback along both faces, also on edges where the faces are not perpendicular.

Shell​

shell hollows a part to walls of a given thickness, leaving the chosen faces open:

Shell before rounding the rim: removing a face that is surrounded by fillets is a case the kernel cannot do.

cup = Cylinder(20, 30).shell(2, Cylinder(20, 30).faces().top())
case = Box(80, 50, 30).shell(2.5)                # closed, hollow inside
lining = Box(80, 50, 30).shell(2.5, outward=True)  # walls grow outside instead

Offset​

bigger = Box(20, 20, 20).offset(2)       # every face moves out by 2
smaller = Box(20, 20, 20).offset(-2)

Split and section​

part = Box(40, 30, 20) - Cylinder(8, 30)
upper = part.split(Plane.XY)                       # keeps the side the normal points to
lower = part.split(Plane.XY, keep="below")
left, right = part.split(Plane.YZ, keep="both")

cut = part.section(Plane.XY)                       # the cross-section, as a sketch
print(cut.area)                                    # 40 * 30 - pi * 8^2

Mirror​

half = Box(20, 10, 10).translate(10, 0, 0)
half = half.fillet(half.edges().right(), 2)
whole = half + half.mirror(Plane.YZ)

Draft​

Drafted walls come from tapered extrusions:

mold_core = RoundedRectangle(60, 40, 5).extrude(20, taper=3)

Repair and conversion​

healed = part.heal()          # mend gaps and tolerances, mostly for imported data
nurbs = part.to_nurbs()       # every face and edge as NURBS