Build-time vertex compression

Pivot Painter stores per-vertex lookup data in mesh UV channels. Unity’s Player Settings → Other Settings → Vertex Compression can convert UV channels to fp16 in builds (the editor always uses fp32), which quantizes that data. This note documents the verified numeric limits (measured 2026-07-02) and what to do about them.

PP2 texture mode (default)

The lookup channel (UV3 by default) stores texel-center coordinates (x+0.5)/W, the element index (z, used only for phase seeding/debug) and packed level/flag metadata (w).

Payload	fp16 behavior
Texel centers, texture width ≤ 1024	exact — no action needed
Texel centers, fixed width ≥ 2048	lands on the wrong texel — corrupt decode in builds
Element index in z	exact ≤ 2048, corrupts above (phase/debug only — cosmetic)
Level/flag metadata in w	dyadic values — survives fp16 exactly (all 16 combos verified)

Auto texture sizing never exceeds 256×256 at the 30,000-element cap, so the default configuration is always safe. The bake emits a report warning when a Fixed texture width ≥ 2048 is used.

PP1 mesh-data mode

PP1 packs pivot positions and axis/extent data directly into UV channels as floats. These quantize badly under fp16 (pivots drift by centimeters on meter-scale assets — visible joint cracks in builds).

Recommendations

1. Prefer Auto texture sizing (default) — always within fp16-safe range for PP2.
2. If you must use Fixed ≥ 2048, or PP1 mode, exclude the payload channels from Vertex Compression: Player Settings → Vertex Compression → uncheck TexCoord (or use per-channel control where available), or set the project’s Vertex Compression to None for foliage-heavy targets.
3. The forensic decoder (EQ Tools → Pivot Painter Lab → Diagnostics) runs on editor data and will NOT show build-only corruption — verify a development build visually when using Fixed large textures with compression enabled.