# `PartWriteOptions.fadeMs`

> Contract 2.0.0 · package sha256 `a857eca95b35921109faf997094bb4192f12527d9d0fcd4be7e97f06425bad6e` · generated from `configurator-runtime.d.ts` by `services/onsite-scripter/scripts/build-contract-docs.mjs`; edit the source, not this file.

Property of [`PartWriteOptions`](PartWriteOptions.md) · stable · since 2.0.0

```ts
fadeMs?: number;
```

Material crossfade, ms: baseColor, normal, orm and alpha crossfade, each side sampled at its own placement (`uv`, `scale` or `sizeM`, `offset`, `rotationDeg`), and scalars tween on the same clock. A `sheen` whose `enabled` flips tweens its `intensity` from or to 0 on that clock, drawn with the sheen variant from the first faded frame to the last (its weight never below 1e-4 there, which draws as no sheen), so the program changes only when the fade lands, to the target's own. Each part the write changes fades from what it drew, and a part outside it keeps its look, also when it already wears the incoming material. Readiness also prepares every shader the fade draws before the commit is shown, so a fade links none: for a flipping `sheen`, the sheen variant of the material the fade draws. Where the browser can't link shaders in the background (no `KHR_parallel_shader_compile`), preparing is a main-thread link wherever it runs. Where the device's texture units (`MAX_TEXTURE_IMAGE_UNITS`) can't hold the samplers both sides need, the fade blends `baseColor` alone, scalars still tween, and the other maps swap at its first frame, so a click never recompiles. It resolves, starts and is taken over as [`durationMs`](PartWriteOptions.durationMs.md) says, with the material in place of the pose: a newer write to the same rule takes over from what is drawn, its maps from the look this fade goes to once the fade has drawn a frame (a write back to the look it comes from reverses it; before that frame, from the drawn look), and resolves this one (spec section 6.3); a field it writes to this fade's own target value is no takeover. Counts as 0 under reduced motion (spec section 6.2).

**Default:** 0

## Generic-API test (spec 3.1)

| Rule | Result |
| --- | --- |
| 1. Neutral name | pass: `fadeMs` names no product |
| 2. A precedent | pass: [Unity Material.Lerp](https://docs.unity3d.com/ScriptReference/Material.Lerp.html) (row `K17`) |
| 3. Two apps, or labs | pass: 28 apps (ledger: app-04c2774145, app-0c773a4ee3, app-37356bf09f, app-378d190f1b, app-4762caacdc, app-4f16d2f6da, app-4fd23bc869, app-510d750508 and 20 more) |
| 4. The cheaper fix first | decided per need in Appendix B: rows `K17` at tier stable (a member only where no rule, data, asset or app code serves the need) |