Bending and curving

These options reshape what a line makes, after it is made. On a use or a group they reshape the whole part.

twist=, shrink=, bend=

They work by height, from the lowest point of what the line made to the highest:

twist=DEG turns it about the vertical, nothing at the bottom and DEG at the top.
shrink=K narrows it toward the top: K times as wide there (.5 half, 1.5 wider).
bend=DEG curves it over toward +Y, DEG at the top; bend=DEG,HEADING curves it toward HEADING degrees round from +Y.

Use enough pieces for a smooth bend: a box is one piece, so bend a stack of them, or a cylinder with a few rings.

prop twist_demo "Twisted, Shrunk, Bent"
  group at=-1,0,0 twist=90 {
    box at=0,0,on(i*.2) size=.4,.4,.2 mat=stone repeat 10 every 0,0,0
  }
  group shrink=.3 {
    box at=0,0,on(i*.2) size=.4,.4,.2 mat=stone repeat 10 every 0,0,0
  }
  group at=1,0,0 bend=70 {
    box at=0,0,on(i*.2) size=.2,.2,.2 mat=#3a6a2a/plastic repeat 10 every 0,0,0
  }

The gramophone in showpieces.parts bends a flaring cylinder into a horn; the twisted column twists a stack of slices a quarter turn.

smooth=

On pipe, sweep and along=, smooth=N draws a curve through the points instead of straight lines between them, N pieces between each pair. A few points make a cable, a vine, a rail that bends.

try it

prop smooth_demo "Hose"
  pipe mat=#2a5a2a/rubber radius=.03 0,0,.1 .6,.3,.1 .9,-.2,.5 .4,-.4,.9 .1,0,1.1 smooth=6 sides=6

taper=

On pipe and sweep, taper=K narrows the line toward its end: K times its size there. Branches, horns, tusks, tentacles, roots.

try it

prop tentacle_demo "Tentacle"
  pipe mat=#8a4a6a/plastic radius=.12 0,0,0 .1,.1,.6 -.15,.2,1.1 0,.5,1.5 .3,.6,1.6 smooth=5 taper=.1 sides=7

(On box and bevel_box, taper=TX,TY is something else: it scales the top face.)

Rounder shapes from fewer triangles

sides= on round shapes: 6 to 12 is the house style; 3 to 5 for twigs and wires.
smooth=1 on a part shades it smooth instead of faceted.
wobble= (see variety) takes the machine-made look off anything.