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Rigged LOD: un-subdivide meshes with subdivision structure instead of decimating them #612

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opened 2026-10-10 01:15:49 +00:00 by sky_line · 2 comments

sky_line commented

2026-10-10 01:15:49 +00:00

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Proper un-subdivision gives cleaner, more workable reduced meshes than vertex-removal decimation, and one level cuts triangles / vertices about 4x.

Approach (hybrid)

Per rigged source mesh: rebuild quads from triangle pairs, then test for subdivision structure (regular valence, consistent even/odd vertex split, quad rings). Quad-modelled bases and heads usually have it; Marvelous Designer clothing, sculpted props and already-decimated creator LODs usually don't.
If it passes: un-subdivide one or two levels and measure the geometric error, then use it as the step (same error-driven step choice in the cull, same cache, shadow LOD and RT replay).
Prefer a real reverse subdivision (solve for the cage) over dropping the odd vertices: the cage lies outside the smoothed surface, so reduced clothing grows slightly instead of sinking into the body (see the clothing-shrinkage ticket).
Otherwise, or if the error is too high: fall back to the current meshoptimizer decimation.
Skin weights, UVs and seams: kept vertices are exact; solved cage positions need weights / UVs carried from the even vertices.

Related: #561, the clothing-shrinkage ticket.

Proper un-subdivision gives cleaner, more workable reduced meshes than vertex-removal decimation, and one level cuts triangles / vertices about 4x. ## Approach (hybrid) - Per rigged source mesh: rebuild quads from triangle pairs, then test for subdivision structure (regular valence, consistent even/odd vertex split, quad rings). Quad-modelled bases and heads usually have it; Marvelous Designer clothing, sculpted props and already-decimated creator LODs usually don't. - If it passes: un-subdivide one or two levels and measure the geometric error, then use it as the step (same error-driven step choice in the cull, same cache, shadow LOD and RT replay). - Prefer a real reverse subdivision (solve for the cage) over dropping the odd vertices: the cage lies outside the smoothed surface, so reduced clothing grows slightly instead of sinking into the body (see the clothing-shrinkage ticket). - Otherwise, or if the error is too high: fall back to the current meshoptimizer decimation. - Skin weights, UVs and seams: kept vertices are exact; solved cage positions need weights / UVs carried from the even vertices. Related: #561, the clothing-shrinkage ticket.

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2026-10-10 01:24:22 +00:00

sky_line referenced this issue

2026-10-10 01:28:56 +00:00

Mesh upload: better auto-generated LODs (attribute / skin-weight aware simplification, vertex placement, error shown in the UI) #618

sky_line referenced this issue from a commit

2026-10-10 03:31:54 +00:00

#612: un-subdivide rigged meshes -- the 1/4 decimated step undoes one Catmull-Clark level when the source has one

sky_line referenced this issue from a commit

2026-10-10 03:31:54 +00:00

#612: RenderVKRigUnsubdivide toggle -- no rebuild / log when nothing is built yet (setting off at startup)

sky_line commented

2026-10-10 05:32:59 +00:00

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Built and pushed (9aeee8dea7, 2d5d56b7a5; RenderVKRigUnsubdivide), shipped in 1.2.0. Not yet verified in-world on real rigged content, so it moves from In Progress to Testing: waiting on an in-world check that subdivided avatar meshes reduce cleanly and non-subdivided ones fall back to decimation.

Built and pushed (9aeee8dea7, 2d5d56b7a5; RenderVKRigUnsubdivide), shipped in 1.2.0. Not yet verified in-world on real rigged content, so it moves from In Progress to Testing: waiting on an in-world check that subdivided avatar meshes reduce cleanly and non-subdivided ones fall back to decimation.

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2026-10-10 05:32:59 +00:00

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2026-10-10 12:52:36 +00:00

[Epic] Cluster LOD (meshlets + DAG, Nanite-style) for avatars, extensible to dense static mesh #642

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