Tutorial R: Beginner masterclass, tube and attractor frames

Video	Rhino Grasshopper Tutorial (Beginner) (YouTube, channel Rhino Grasshopper), 54 minutes
Application	Algorithmic Modeling (Katydid)
You learn	Frames along a curve, sweeping a section, dividing a surface into panels, an attractor with Remap Numbers
Sizes	Millimetres: a tube of radius 9 on a 40 mm rail, 12 × 6 panels, openings 0.6 to 2.6 in radius

The masterclass leans on three plugins: Bifocals (labels), LunchBox (panels) and Weaverbird (mesh frames, subdivision, thickening). Katydid has no plugins and no mesh tools, so this page rebuilds what its own components can: the tube, the panel grid and openings that grow near an attractor. Each opening gets a frame ring, standing in for Weaverbird’s picture frames.

Step by step

1. Set-up

Plugin installation (File › Special Folders › Components Folder, Unblock) has no counterpart. Grasshopper’s Draw Fancy Wires is how Katydid always draws: solid for one item, double for a list, dashed for a tree of several branches.

2. The tube

Circle, a Rail radius slider (40): the rail.
Evaluate Curve at a Frame t slider (0 to 1): its point and tangent are the frame Grasshopper’s Perp Frame gives. Katydid’s t always runs 0 to 1, so there is nothing to Reparameterize.
Circle CNR (centre, normal, radius) with a Tube radius slider (9): the section on that frame.
Pipe sweeps it along the rail (the video’s Sweep 1; a round section is all Pipe needs). A Panel shows the result.

The tube’s volume is 63,955 mm³, 2π²Rr² for a torus.

3. The panel grid

The video divides the surface with Divide Domain² and IsoTrim (or LunchBox panels). Here U section circles stand along the rail (a Series of t values into Evaluate Curve and Circle CNR), and Divide Curve splits each into V points: the corners of 12 × 6 panels, all on the tube.

4. The attractor

A Construct Point with three sliders stands in for the MD Slider.
Distance from every corner to it.
Bounds, its input Flattened, gives the nearest and farthest.
Remap Numbers maps the distances onto the opening radii. Two sliders stand in for Construct Domain: Largest (2.6) into T0 and Smallest (0.6) into T1, so the nearest corner gets the largest opening.

5. The frames

A second ring of corners 3 mm further in (Expression x - 3, Circle CNR, Divide Curve).
Vector 2Pt from each corner to its inner twin: the opening’s axis.
Circle CNR with the remapped radii: the openings.
Pipe with a Frame width slider (0.45) turns each opening into a frame.

Drag the attractor sliders and the large frames follow it round the tube.

Opening frames that grow near the attractor

Cutting real holes through a hollow tube was tried first and failed: in the GUI, a second Solid Difference on a Pipe-minus-Pipe wall came back invalid, while the same shapes cut cleanly once read back from a file. It is reported to Katydid.

6. Bake

Select the tube’s Pipe and the frames' Pipe and click Home › Algorithm › Bake: the tube and the 72 frames become Part solids. Live dimensions (Aligned Dimension) and Custom Preview colours have no Katydid counterpart yet.

The replay

#	In the book (NX)	In FreeCAD NX-Style	Result	Notes
R1	Install Bifocals, LunchBox and Weaverbird (Components Folder, Unblock)	-	missing	Katydid has no plugins: everything below uses its own components
R2	Display > Draw Icons, Full Names, Fancy Wires	-	same	Katydid always draws its wires 'fancy': solid for one item, double for a list, dashed for a tree of several branches
R3	Circle rail; Perp Frame at t (Reparameterize: 0 to 1); a section Circle on that frame; Sweep 1	Circle (rail), Evaluate Curve at 'Frame t' (its point and tangent are the frame: Katydid’s t always runs 0 to 1), Circle CNR (centre, normal, radius) for the section; Pipe for the sweep; a Panel shows the result	differs	tube 63955 mm^3 (a torus, 2 pi^2 R r^2 = 63955). No Perp Frame or Sweep 1 component yet: a circle section swept along a rail is Katydid’s Pipe
R4	Divide Domain2 into U x V; IsoTrim the surface into panels (or LunchBox Quad Panels)	stand-in: U section circles along the rail (Series of t, Evaluate Curve, Circle CNR), each divided into V points: the corners of U x V panels	missing	72 panel corners, all on the tube (within 0.0000 mm). Katydid has no Divide Domain2, IsoTrim or panelling components yet
R5	Mesh Surface; Weaverbird Picture Frame, Weld, Catmull-Clark (level 1-3), Thicken	-	missing	no mesh components or Weaverbird counterpart in Katydid: the next step frames each opening with a ring instead of insetting mesh faces
R6	Attractor: Evaluate Surface at an MD Slider’s uv; Closest Point distances; Bounds; Construct Domain; Remap Numbers into the opening sizes	Construct Point with X/Y/Z sliders (no MD Slider yet); Distance from every panel corner; Bounds (input Flattened); Remap Numbers into 'Smallest' .. 'Largest' (two sliders for the target domain)	differs	72 opening radii from 0.6000000000000001 to 2.6 mm; the corner nearest the attractor gets 2.6 ('Largest' into T0, 'Smallest' into T1). Katydid has no MD Slider or Construct Domain yet
R7	Graft the remapped sizes into Weaverbird’s Picture Frame distance: the openings grow near the attractor; Weld, Catmull-Clark and Thicken round and thicken the frames	a second ring of corners 3 mm further in (Expression x - 3, Circle CNR, Divide Curve); Vector 2Pt from each corner to its inner twin as the opening’s axis; Circle CNR with the remapped radii; Pipe with a 'Frame width' slider makes each opening’s frame	differs	72 frames (72 valid solids) on the tube (centres within 1.6e-14 mm), openings 0.6 to 2.6 mm in radius, the largest nearest the attractor; drag the attractor sliders and they follow. Katydid has no mesh components: the frames are rings, not inset mesh faces
R8	Deconstruct Brep, List Item and Aligned Dimension for live dimensions; Custom Preview colours	-	missing	no drawing dimensions or preview colours on Katydid’s canvas yet
R9	Right-click > Bake to a Rhino layer	select the tube’s Pipe and the frames' Pipe + ribbon 'Home › Algorithm > Bake'	same	73 objects baked (the tube and 72 frames), 73 valid; FreeCAD has no layers here: they go into the Part Navigator

In the book (NX)

In FreeCAD NX-Style

Result

Notes

Install Bifocals, LunchBox and Weaverbird (Components Folder, Unblock)

missing

Katydid has no plugins: everything below uses its own components

Display > Draw Icons, Full Names, Fancy Wires

same

Katydid always draws its wires 'fancy': solid for one item, double for a list, dashed for a tree of several branches

Circle rail; Perp Frame at t (Reparameterize: 0 to 1); a section Circle on that frame; Sweep 1

Circle (rail), Evaluate Curve at 'Frame t' (its point and tangent are the frame: Katydid’s t always runs 0 to 1), Circle CNR (centre, normal, radius) for the section; Pipe for the sweep; a Panel shows the result

differs

tube 63955 mm^3 (a torus, 2 pi^2 R r^2 = 63955). No Perp Frame or Sweep 1 component yet: a circle section swept along a rail is Katydid’s Pipe

Divide Domain2 into U x V; IsoTrim the surface into panels (or LunchBox Quad Panels)

stand-in: U section circles along the rail (Series of t, Evaluate Curve, Circle CNR), each divided into V points: the corners of U x V panels

missing

72 panel corners, all on the tube (within 0.0000 mm). Katydid has no Divide Domain2, IsoTrim or panelling components yet

Mesh Surface; Weaverbird Picture Frame, Weld, Catmull-Clark (level 1-3), Thicken

missing

no mesh components or Weaverbird counterpart in Katydid: the next step frames each opening with a ring instead of insetting mesh faces

Attractor: Evaluate Surface at an MD Slider’s uv; Closest Point distances; Bounds; Construct Domain; Remap Numbers into the opening sizes

Construct Point with X/Y/Z sliders (no MD Slider yet); Distance from every panel corner; Bounds (input Flattened); Remap Numbers into 'Smallest' .. 'Largest' (two sliders for the target domain)

differs

72 opening radii from 0.6000000000000001 to 2.6 mm; the corner nearest the attractor gets 2.6 ('Largest' into T0, 'Smallest' into T1). Katydid has no MD Slider or Construct Domain yet

Graft the remapped sizes into Weaverbird’s Picture Frame distance: the openings grow near the attractor; Weld, Catmull-Clark and Thicken round and thicken the frames

a second ring of corners 3 mm further in (Expression x - 3, Circle CNR, Divide Curve); Vector 2Pt from each corner to its inner twin as the opening’s axis; Circle CNR with the remapped radii; Pipe with a 'Frame width' slider makes each opening’s frame

differs

72 frames (72 valid solids) on the tube (centres within 1.6e-14 mm), openings 0.6 to 2.6 mm in radius, the largest nearest the attractor; drag the attractor sliders and they follow. Katydid has no mesh components: the frames are rings, not inset mesh faces

Deconstruct Brep, List Item and Aligned Dimension for live dimensions; Custom Preview colours

missing

no drawing dimensions or preview colours on Katydid’s canvas yet

Right-click > Bake to a Rhino layer

select the tube’s Pipe and the frames' Pipe + ribbon 'Home › Algorithm > Bake'

same

73 objects baked (the tube and 72 frames), 73 valid; FreeCAD has no layers here: they go into the Part Navigator

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.