Tutorial Q: Faceted planter

Video	Rhino Grasshopper Tutorial (Beginner) (YouTube, channel Rhino Grasshopper)
Application	Algorithmic Modeling (Katydid), then Modeling for the shell
You learn	Rotating by a formula, lists and data trees (Shift, Graft, Flatten), facets from points, joining faces into a solid, a shell
Sizes	Millimetres: a pentagon of radius 30, 60 high, walls 3 thick

For the facets to be triangles, each top corner must sit over the middle of a base edge. The angle between corners is 360°/N, so the top polygon turns by half of it: 36° for a pentagon.

Step by step

1. The base polygon

Regular Polygon with a Radius slider (10 to 50, here 30) and a Segments slider (3 to 8, here 5).

2. The top polygon

Move it up by a Height slider (60) and Rotate it by an Expression 360/x/2, with the Segments slider as x. The video uses two Division components and a Unit Z vector; Katydid’s Move takes the height directly, and Rotate works in degrees.

3. Corners and their neighbours

The video Explodes both polygons and trims the repeated closing vertex with Shortest List. Katydid’s Divide Curve into Segments gives the corners without the repeat, so no Shortest List is needed.

Shift List by 1 gives each corner’s neighbour. Then come the data trees:

Graft the corner lists (right-click an output › Graft): each corner gets its own branch, so the next component builds one facet per corner.
Flatten Shift List’s input first: Shift List adds a level to the path, and without the Flatten its branches would not line up with the others.

4. The facets

The video uses Extrude Point (an edge drawn to a point). Here a closed Polyline through three corners does the same, then Planar Surface:

lower facets: base corner, next base corner, top corner;
upper facets: top corner, next top corner, next base corner.

The shifted lists keep the facets from twisting: ten triangles.

5. A closed solid

The video caps the openings with Boundary Surfaces and joins everything with Brep Join. Here Solid Union, its input Flattened, joins the ten facets into one shell, and Cap Holes closes the top and the bottom: a valid solid of 12 faces and 138,495.8 mm³, exactly what FreeCAD’s Part API gives for the same faces.

6. Bake and shell

The video’s Option A bakes the solid and runs Rhino’s Shell. Here the same happens with FreeCAD:

Select Cap Holes and click Home › Algorithm › Bake.
Ctrl+M (Modeling), click the top face of the baked solid.
Surface › Surface Operations › Thicken (FreeCAD’s Part Thickness), type -3 mm, tick Intersection, MB2.

Without Intersection, FreeCAD 1.1.4 returns this faceted solid unchanged. With it, the planter is hollow and open at the top, its outside unchanged.

The video’s Option B, Pufferfish’s parametric Shell Polysurface, has no Katydid component yet.

The replay

#	In the book (NX)	In FreeCAD NX-Style	Result	Notes
Q1	Open Grasshopper	Ctrl+N + Application > Algorithmic Modeling	same	an empty canvas on the new part
Q2	Polygon on the XY plane; sliders for Radius (10-50) and Segments (3-8)	Regular Polygon with 'Radius' 30 and 'Segments' 5	same	5 edges, corners 30.000 mm from the centre
Q3	Move it up by Unit Z x height; Rotate 3D by 360 / N / 2 degrees (two Divisions)	Move with 'Height' in Z; Rotate with A = Expression 360/x/2 (x = Segments); Katydid’s Rotate takes degrees	differs	top polygon at z = 60.0, first corner at 36.0 degrees (360 / 5 / 2 = 36): each top corner sits over the middle of a base edge
Q4	Explode both polygons; Shortest List drops the repeated closing vertex; Shift List by 1	stand-in for Explode: Divide Curve into Segments (corners, without the repeated closing one, so no Shortest List is needed); Shift List with its input Flattened; the lists for the facets Grafted, one corner per branch	missing	corners per list {'bv': 5, 'tv': 5, 'bs': 5, 'ts': 5}. Katydid has no Explode or Shortest List yet (asked for)
Q5	Extrude Point: each base edge to a top corner, then each top edge to the shifted base corner	stand-in for Extrude Point: a closed Polyline through each branch’s three corners (base, next base, top / top, next top, next base), then Planar Surface	missing	10 triangular facets, 10628 mm^2; Shift List keeps them from twisting. Katydid has no Extrude Point yet (asked for)
Q6	Boundary Surfaces for the top and bottom caps; everything Flattened into Brep Join: a closed solid	Solid Union with its input Flattened joins the ten facets into one shell; Cap Holes closes the top and bottom	differs	valid solid, 12 faces, 138495.8 mm^3 (the same faces made directly with FreeCAD’s Part API: 138495.8). Cap Holes makes both caps, so no separate Boundary Surfaces are needed
Q7	Bake the solid	select Cap Holes + ribbon 'Home › Algorithm > Bake'	same	Cap 0, 138495.8 mm^3
Q8	Shell: Rhino’s Shell command, the top face picked, thickness 5 (or Pufferfish’s Shell Polysurface)	the top face selected + ribbon 'Surface › Surface Operations > Thicken' (FreeCAD’s Part Thickness), '-3 mm' typed, Intersection ticked, MB2 = OK	differs	hollow planter 35097.5 mm^3 of 138495.8, outside unchanged True, 23 faces; value -3.0 mm. Option B (Pufferfish’s parametric Shell) has no Katydid component yet

In the book (NX)

In FreeCAD NX-Style

Result

Notes

Open Grasshopper

Ctrl+N + Application > Algorithmic Modeling

same

an empty canvas on the new part

Polygon on the XY plane; sliders for Radius (10-50) and Segments (3-8)

Regular Polygon with 'Radius' 30 and 'Segments' 5

same

5 edges, corners 30.000 mm from the centre

Move it up by Unit Z x height; Rotate 3D by 360 / N / 2 degrees (two Divisions)

Move with 'Height' in Z; Rotate with A = Expression 360/x/2 (x = Segments); Katydid’s Rotate takes degrees

differs

top polygon at z = 60.0, first corner at 36.0 degrees (360 / 5 / 2 = 36): each top corner sits over the middle of a base edge

Explode both polygons; Shortest List drops the repeated closing vertex; Shift List by 1

stand-in for Explode: Divide Curve into Segments (corners, without the repeated closing one, so no Shortest List is needed); Shift List with its input Flattened; the lists for the facets Grafted, one corner per branch

missing

corners per list {'bv': 5, 'tv': 5, 'bs': 5, 'ts': 5}. Katydid has no Explode or Shortest List yet (asked for)

Extrude Point: each base edge to a top corner, then each top edge to the shifted base corner

stand-in for Extrude Point: a closed Polyline through each branch’s three corners (base, next base, top / top, next top, next base), then Planar Surface

missing

10 triangular facets, 10628 mm^2; Shift List keeps them from twisting. Katydid has no Extrude Point yet (asked for)

Boundary Surfaces for the top and bottom caps; everything Flattened into Brep Join: a closed solid

Solid Union with its input Flattened joins the ten facets into one shell; Cap Holes closes the top and bottom

differs

valid solid, 12 faces, 138495.8 mm^3 (the same faces made directly with FreeCAD’s Part API: 138495.8). Cap Holes makes both caps, so no separate Boundary Surfaces are needed

Bake the solid

select Cap Holes + ribbon 'Home › Algorithm > Bake'

same

Cap 0, 138495.8 mm^3

Shell: Rhino’s Shell command, the top face picked, thickness 5 (or Pufferfish’s Shell Polysurface)

the top face selected + ribbon 'Surface › Surface Operations > Thicken' (FreeCAD’s Part Thickness), '-3 mm' typed, Intersection ticked, MB2 = OK

differs

hollow planter 35097.5 mm^3 of 138495.8, outside unchanged True, 23 faces; value -3.0 mm. Option B (Pufferfish’s parametric Shell) has no Katydid component yet

Result	Means
same	The book’s NX steps work as written.
differs	It works, but the FreeCAD way is different; the notes say how.
limit	The book’s way fails in FreeCAD itself; a workaround follows in the next steps.
missing	FreeCAD has no such function; a stand-in follows.
skipped	Not replayed; the notes give the reason.
FAILED	Did not work.

Result

Means

same

The book’s NX steps work as written.

differs

It works, but the FreeCAD way is different; the notes say how.

limit

The book’s way fails in FreeCAD itself; a workaround follows in the next steps.

missing

FreeCAD has no such function; a stand-in follows.

skipped

Not replayed; the notes give the reason.

FAILED

Did not work.