Particles → VDB surface

Surfacing particles as VDB blobs (verified)

dopimport (objpattern popobject1) → vdbfromparticles → vdbsmoothsdf → convertvdb → attribtransfer → null

• vdbfromparticles: voxelsize ≈ ⅓ of particle radius (0.004 for pscale 0.012), radiusscale 1.4 so neighbours in a clump overlap and fuse, minvoxelradius 1.0, bandwidthvoxels 3.
• vdbsmoothsdf: operation='meanvalue', radius 1, iterations 3 — rounds the blobs.
• convertvdb: conversion='poly', adaptivity 0.15, computenormals 1.
• attribtransfer (input 1 = the particles): primitiveattribs=0, pointattribs=1, pointattriblist='Cd', kernelradius ~2.5× pscale, maxsamplecount 4 — surface inherits the particle colour ramp.
• Verified on 10k particles: ~0.15 s/frame, 50–65k polys; 20k: ~0.2 s/frame, ~115k polys.
• Judge fusing by blob count and the largest blob's share of polys: connectivity SOP with connecttype='prim' (default is point → no prim class), count prims per class.
• When particle count changes, rescale radiusscale by (density ratio)^(-1/3). Verified: doubling to 20k at 1.4 fused 70% of the fuel into one body; 1.4 × 0.79 ≈ 1.1 gave 237 blobs, largest 20% (10k at 1.4: 112 blobs, largest 24%).

Keeping this skill current

After any session that used Houdini/Cinema 4D via MCP, or whenever something new is verified:

1. Add gotchas/recipes ONLY if tested and working in a real scene; mark anything else "(unverified)".
2. Correct entries that proved wrong — don't append contradictions.
3. Put each finding in the skill it belongs to (see the indexes in houdini-mcp and cinema4d-mcp); project-specific facts go to that project's notes (see project-notes), never into a skill.
4. Keep each SKILL.md under ~300 lines; split into a new sub-skill or references/ when it grows.
5. Re-package every changed skill (keep names) and, if the skills live in a git repo, commit and push. Tell the user in one line what changed.