Allows for multiface painting of meshes

[jsdbroughton]

Status: Discussion / RFC — Not for merge

Scope: Revit mesh conversion only. No changes to other hosts.

Enables per-face colouring by grouping faces by material and building geometry per material. This avoids Revit’s tendency to collapse mixed-material face sets into a single mesh with a single averaged colour.

Why
Revit meshes carry one MaterialElementId. A single connected build often “browns out” multi-material meshes. Building per material preserves face colours (e.g., Rhino → Speckle → Revit analysis/heatmap meshes).

How (high level)

• Average vertex colours per face (quantised) → resolve/create material.
• Group faces by that material.
• Build geometry per group so Revit emits distinct chunks with distinct materials.

Gating / Performance
This path is gated to avoid surprises on large models. Suggested modes:

• Off (fast path; current behaviour).
• Auto (default): enable only when colours exist and predicted material groups are below a cap (e.g., 256) and face count below a threshold.
• Force: always enable (for Grasshopper / Automate / analysis runs).

What’s not included

• No view/graphics tweaks; no GraphicsStyle/“hide edges” wiring in this PR. If we ship this for analysis meshes, we could optionally add a “no-edges” subcategory later to clean up visuals in Shaded.
• No appearance assets (Realistic mode). Shaded is the target for this iteration.

Behaviour notes

• If an explicit display material exists, vertex colours only override when allowed by settings.
• Colour quantisation caps material proliferation (defaults can be tuned).
• Non-planar quads are split; n-gons have a safe fallback triangulation.

Risks / Trade-offs
More geometry objects and more materials are enabled; costs scale with face count and unique colours. Hence the gating.

Questions

• Is the Auto/Off/Force gating sensible forthe default connector vs. GH/Automate?
• Reasonable defaults for material cap/face threshold?
• Appetite to add optional “no-edges” styling in a follow-up specifically for analysis meshes?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.20%. Comparing base (ea97630) to head (b1adeb0).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

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  Coverage   41.20%   41.20%           
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  Files         109      109           
  Lines        3080     3080           
  Branches      293      293           
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  Hits         1269     1269           
  Misses       1765     1765           
  Partials       46       46           

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[libnypacheco]

This is wonderful, Jonathon!