LLM-RAG Generator Spiral Staircase (Grasshopper C# | 00–09 STEP pipeline)

Spiral Staircase / General CAD LLM-RAG Generator (Grasshopper C# | 00–09 STEP pipeline) is a production-minded parametric CAD system where prompts don’t “draw” — they author structured parameters (CFG) that reliably drive a clean, editable Brep-based staircase assembly.

You get a repeatable loop:

Prompt → CFG/SFG overrides → Helix skeleton → Treads → Core/Stringers → Rail/Guard → Landings → Detailing → QA/Export

It’s built to be:

• Visibly responsive: small prompt changes can push turns, step count, radii, tread/rail density, landing patterns, etc.
• Stable in Grasshopper: hard caps on segmentation + time budgets.
• Fabrication-friendly: solids produced primarily via capped extrusions (boolean-light).
• Reusable: swap the CFG key set + RAG corpus and you’ve got a new parametric product line.

Bonus: the annoying RhinoCommon mismatch bug is handled —

'Brep' does not contain a definition for 'CreateFromExtrusion'

is fixed by using Extrusion.Create(...) (with solid caps) and a robust fallback to Surface.CreateExtrusion(...) + CapPlanarHoles(...) (patched in STEP_03 + STEP_06).

README.txt contents (full)

(Identical to the downloadable file.)

WICKERSON STUDIOS — SPIRAL STAIRCASE / GENERAL CAD LLM-RAG PIPELINE

README.txt (vCAD_RAG1.0 — Grasshopper C# Script Series 00_STEP … 09_STEP)

================================================================================

WHAT THIS IS

------------

This is a 10-node Grasshopper (C# Script) “LLM-RAG CAD generator” pipeline that

builds a high-LOD spiral staircase assembly from a text/image prompt.

The series is designed to feel like a production CAD pipeline:

00_STEP INIT / Master CFG+SFG / EngineState (JSON)

01b_STEP LLM prompting (OpenAI Responses API) -> CFG/SFG overrides + RAG docs

02_STEP Helix spine + step planes (parametric skeleton)

03_STEP Treads (solid wedge steps) ✅ includes safe extrusion fix

04_STEP Stringers + center core (structural solids)

05_STEP Rail / guard / balusters (safety/handrail geometry)

06_STEP Landings (platforms) ✅ includes safe extrusion fix

07_STEP Detailing pass (nosing, chamfers, fasteners, perforations)

08_STEP Assembly / tagging / drawing aids (leaders, labels, outlines)

09_STEP Export + QA (stats, sanity checks, baking helpers, OBJ/3DM stubs)

The core idea:

- The prompt DOES NOT directly “draw geometry.”

- Instead, the LLM returns a strict, structured set of *CFG keys* (numbers + enums)

that drive downstream geometry deterministically.

- The RAG corpus supplies precedent + style hints (e.g. stair types, materials,

code-driven proportions), and the LLM can rewrite/extend that corpus per prompt.

If you don’t provide an API key, the pipeline still works: it uses deterministic

fallback values so the Grasshopper definition is always runnable.

WHAT YOU GET

------------

- A repeatable “prompt -> parameters -> CAD” workflow (no black box mesh magic).

- High-LOD solids suitable for render, documentation, and fabrication prep.

- Hard performance caps (segment counts + time budgets) so GH recomputes stay sane.

- A reusable architecture for ANY parametric CAD generator (swap the CFG keys +

RAG corpus and you have a new product line).

WHY IT’S DIFFERENT (THE WICKERSON WAY)

--------------------------------------

Most “AI CAD” ideas stop at images. This system generates *editable geometry*

through a real CAD pipeline and a structured prompt interface.

You can:

- iterate quickly with prompts,

- keep geometry stable + boolean-safe,

- and still get clear, visible differences every run.

Quick pitch:

“A prompt-driven spiral staircase generator that outputs clean Breps,

plus a framework you can reuse for any parametric CAD product.”

SYSTEM REQUIREMENTS

-------------------

- Rhino 7 or Rhino 8 + Grasshopper

- C# Script component (Grasshopper built-in)

- Internet access ONLY for STEP_01b if using OpenAI

- Optional: An OpenAI API key (kept private; do NOT hardcode in GH files)

SECURITY / COST NOTE

--------------------

- STEP_01b calls https://api.openai.com/v1/responses when API_KEY is provided.

- API usage costs money. Keep prompts concise and use “cached signature” logic.

- Never share your API key in public GH files.

PIPELINE WIRING (HIGH LEVEL)

----------------------------

Every STEP passes forward a JSON string called STATE:

STATE_OUT -> STATE_IN

Suggested GH component names:

00_STEP_INIT

01b_STEP_LLM_CFG_SFG

02_STEP_HELIX_PLANES

03_STEP_TREADS

04_STEP_STRINGERS_CORE

05_STEP_RAIL_GUARD

06_STEP_LANDINGS

07_STEP_DETAILING

08_STEP_ASSEMBLY_TAGS

09_STEP_EXPORT_QA

The key wiring pattern:

00 STATE_OUT -> 01b STATE_IN -> 02 STATE_IN -> 03 STATE_IN -> ... -> 09 STATE_IN

02 StepPlanesOut -> 03 StepPlanesIn -> 06 StepPlanesIn -> (others)

02 StepAnglesOut -> 03 StepStartAngleDegIn -> 06 StepStartAngleDegIn

Run toggles:

- Put a boolean “Run” into each step.

- For stable iteration, only toggle the steps you need to recompute.

MASTER CFG (CANONICAL KEY SET FOR SPIRAL STAIRCASE)

---------------------------------------------------

Paste the CFG string into 00_STEP (cfg input) and/or allow 01b_STEP to override.

NOTE:

If your STEP_01b “ALLOWED keys” list is still bridge-specific, update that list to

match the staircase keys below so prompts visibly affect the geometry.

--- MASTER CFG (copy/paste) ---

brand=Wickerson Studios

project=Spiral Staircase LLM-RAG CAD Generator — vCAD_RAG1.0

cta=https://www.wickersonstudios.com

# units + tolerances

units=m

grid=1.0

snapTol=0.01

basePlane=WorldXY

# staircase drivers

direction=ccw # ccw | cw

stepCount=42

turns=1.25 # total revolutions

totalRiseM=3.15 # total vertical rise

riserH=0.075 # if set, can override stepCount in STEP_02 (optional)

treadW=0.90

nosing=0.02

outerRM=1.35

innerRM=0.15

stepThk=0.06

maxStepSeg=24 # polyline segments per wedge arc

# core / structure

coreType=center_column # center_column | none

coreRM=0.10

coreWallThk=0.02

stringerType=outer # outer | inner | double | none

stringerThk=0.03

stringerH=0.18

# rail / guard

railEnable=true

railH=0.95

railDia=0.04

balusterEnable=true

balusterDia=0.018

balusterSpacing=0.12

guardPanelEnable=false

guardPanelThk=0.010

# landings

landingEnable=true

landingAtBottom=true

landingAtTop=true

landingEveryN=0 # 0 disables intermediate landings; try 12 for every 12 steps

landingDepth=1.40

landingW=1.20

landingThk=0.08

maxLandings=8

# detailing (STEP_07)

chamferR=0.005

treadPerforate=false

treadPerfDia=0.018

treadPerfPitch=0.060

fasteners=false

fastenerDia=0.008

# performance caps

booleanBatch=8

timeBudgetSec=8

# RAG controls

ragEnable=true

ragTopK=6

ragMinScore=0.22

ragDiversity=0.35

# LLM controls (01b)

llmModel=gpt-5.2 # often hardcoded in 01b for safety/consistency

llmMaxOut=1400

llmTemp=0.25

MASTER SFG (STRUCTURED FOCUS GUIDANCE)

--------------------------------------

This is the “creative + intent” channeling text. It’s meant to be detailed and

CAD-facing. Paste into 00_STEP (sfg input) and/or allow 01b to rewrite/extend it.

--- MASTER SFG (copy/paste) ---

reference: High-LOD spiral stair precedents: industrial steel helix with crisp tread rhythm, center column + outer stringer, clean welded logic, code-like consistency. Emphasize strong silhouette and readable structural hierarchy (core -> stringer -> treads -> guard).

program: Interior stair assembly for architectural massing studies; fabricate-friendly solids; stable recompute in Grasshopper; clear handrail/guard components.

style: Engineering-forward, minimal, precise. Avoid noisy ornament unless prompted. Prioritize legibility: treads read as repeated wedge modules, rail reads as continuous curve with evenly spaced verticals.

massing: Helix spine sets the primary sweep; step planes sample along the helix. Treads are wedge solids (inner->outer radius) with a subtle nosing. Optional landings at top/bottom and code-like rise/run consistency.

facade: Guard/handrail is the “facade”: continuous top rail, vertical balusters, optional panel infill. Keep everything aligned to step planes and helix tangent for clean flow.

math: turns + stepCount control angular increment; totalRiseM controls vertical increment; radii control wedge geometry; spacing controls baluster density; timeBudget + segment caps keep recompute stable.

notes: Prompts should visibly affect: turns, stepCount, radii, treadW, rail style/density, landing pattern. Keep booleans conservative; prefer extrusions and capped solids for robustness.

PROMPTING (WHAT TO TYPE INTO 01b)

---------------------------------

Use 01b “Prompt” as the driver. Good prompts combine style + proportions + material.

Example prompts:

1) “Brutalist concrete spiral stair, thick treads, wide outer radius, minimal guard, heavy landings.”

2) “Lightweight industrial steel spiral, thin treads, dense balusters, tight inner core, 1.75 turns.”

3) “Museum stair: generous landings, elegant sweeping rail, low step rise, airy spacing.”

The point: your prompt should cause 01b to override CFG values like:

turns, stepCount, totalRiseM, outerRM, innerRM, treadW,

railEnable/balusterSpacing, landingEveryN, landingDepth/landingW, etc.

KNOWN FIXES (ALREADY PATCHED IN THIS CHAT)

------------------------------------------

If you saw this compile error:

'Brep' does not contain a definition for 'CreateFromExtrusion'

That is now fixed by replacing it with a safe helper:

Extrusion.Create(profile, height, cap:true) -> ToBrep()

fallback: Surface.CreateExtrusion(...) -> CapPlanarHoles(tol)

This patch is applied in:

- STEP_03 (Treads)

- STEP_06 (Landings)

TROUBLESHOOTING

---------------

1) Empty geometry outputs:

- Confirm upstream wires: StepPlanes + angle lists must match counts.

- Confirm Run=true and timeBudgetSec not too low.

2) Weird rotations:

- Your StepPlanes may not have consistent X/Y axes assumptions.

- Fix by reorienting planes from helix tangent + global axis in STEP_02.

3) Caps fail / invalid Breps:

- Increase snapTol slightly (0.02).

- Ensure innerRM < outerRM - treadW margin.

- Reduce maxStepSeg if the boundary self-intersects.

4) Performance:

- Lower stepCount, maxStepSeg, baluster density.

- Keep timeBudgetSec realistic (6–12 sec).

LICENSE / USE

-------------

Use this as a boilerplate for your own generators and products.

If you’re distributing, keep your OpenAI key out of the file.

WICKERSON STUDIOS

----------------

If you want the “full pack” version (all steps fully built, labeled, QA’d, and

with multiple staircase archetypes + prompt presets), publish it as a

Wickerson Studios download and iterate the CFG keys the way you like.

Site: https://www.wickersonstudios.com