pointcloud-generator

name	pointcloud-generator
description	Generate a colour-coded 3D point cloud (.xyz + .pcd) for bioinspired hierarchical ribbed membrane lattices — Cricket wing harp layer, Cicada tymbal corrugation layer, and multi-scale hierarchical lattice layer. Each structural element is analytically sampled (pure numpy, no LLM, no OpenSCAD) and assigned a distinct RGB colour. Produces ASCII XYZ, PCL v0.7 ASCII PCD, and a 4-panel PNG (isometric, top-XY, side-XZ, side-YZ). Chainable downstream of pointcloud-generator or upstream of fem-analysis.
metadata	{"category":"materials-design","requires":"numpy, matplotlib, mpl_toolkits"}

Point Cloud Generator

Generates a 3D point cloud for a Hierarchical Ribbed Membrane Lattice inspired by Gryllus bimaculatus (cricket wing harp) and cicada tymbal geometry.

Three structurally distinct Z-layers are sampled analytically:

Layer	Z offset	Structural feature	Colour
Cricket harp	0 mm	Base membrane + diagonal file ridge + parallel harp veins	grey / red / orange
Cicada tymbal	+1.5 mm	Cosine-graded corrugation ribs (tall centre, zero at edges)	blue
Hierarchical lattice	+3.0 mm	Primary / secondary / tertiary rib scales (3 densities)	dark / mid / light green

Usage

# From inline JSON spec
python3 {baseDir}/scripts/pointcloud_generator.py \
  --spec '{"biological_inspiration":"Cricket wing harp + Cicada tymbal",
           "rib_spacing_mm":2.5,"thickness_mm":0.4,"aspect_ratio":2.5,"num_scales":3}' \
  --output-dir /tmp/pointcloud_out

# From spec file
python3 {baseDir}/scripts/pointcloud_generator.py \
  --spec-file /path/to/spec.json \
  --output-dir /tmp/pointcloud_out

Output JSON (stdout)

{
  "xyz_path":  "/tmp/pointcloud_out/membrane_lattice.xyz",
  "pcd_path":  "/tmp/pointcloud_out/membrane_lattice.pcd",
  "png_path":  "/tmp/pointcloud_out/pointcloud_views.png",
  "total_points": 18348,
  "bounding_box_mm": {"x_min":0,"x_max":50,"y_min":0,"y_max":120,"z_min":-0.07,"z_max":3.80},
  "layers": {
    "cricket_harp":       {"points": 11496, "z_mm": 0.0}
              
       
  

Output Files

File	Format	Description
membrane_lattice.xyz	ASCII x y z r g b	Standard XYZ+RGB, one point per line
membrane_lattice.pcd	PCL v0.7 ASCII	Compatible with PCL, CloudCompare, Open3D
pointcloud_views.png	PNG	4-panel matplotlib figure, dark background

Geometry Parameters (from spec)

Field	Default	Effect
rib_spacing_mm	2.5	Primary rib pitch; secondary = ÷3, tertiary = ÷6
thickness_mm	0.4	Base membrane thickness; controls Z roughness
aspect_ratio	2.5	H = W × aspect_ratio (W fixed at 50 mm)
num_scales	3	Number of rib hierarchy levels (2 or 3)

Chaining

# Generate point cloud then run FEM on same spec
PCD=$(python3 skills/pointcloud-generator/scripts/pointcloud_generator.py \
        --spec '{"rib_spacing_mm":2.5,"thickness_mm":0.4}' \
        --output-dir /tmp/out | jq -r '.pcd_path')

python3 skills/fem-analysis/scripts/mechanism_analysis.py \
  --stl /tmp/out/membrane_lattice.xyz \   # FEM reads bounding box from any 3D file
  --topology cricket_harp \
  --rib-spacing-mm 2.5 --rib-height-mm 0.8

Colour Legend

■ grey   (180,180,180)  Base membrane
■ red    (220, 50, 50)  Diagonal file ridge (cricket harp)
■ orange (220,140, 50)  Harp veins (X-parallel)
■ blue   ( 50,100,220)  Cicada tymbal corrugation ribs (graded height)
■ dark ■ (20,120,50)    Primary ribs — level 1 (coarse, 2.5 mm pitch)
■ mid  ■ (80,180,80)    Secondary ribs — level 2 (medium, 0.83 mm pitch)
■ light■ (160,220,160)  Tertiary ribs — level 3 (fine, 0.42 mm pitch)