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port: the developer splash declares TWO shapes -- and the port draws both, per element

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The publisher shape check covered one element on one screen, which I flagged: a
port applying one screen-wide ramp to everything would have passed it.

developer_logos declares gamearts/seta flat across 15..30 and anima decaying 17%
over the same interval. Same screen, same frames, same clock -- the two flat
elements are the control for the third, and any phase or rate error hits all
three alike.

Pre-registered, then filmed. Flat ones flat to five decimals (+0.00000), anima
decays. Fitted scale-free against declared curves: each element matches its own
at 0.49/0.50/2.18% max error and the OTHER shape at 8.1-8.8% -- 4-17x, both
directions.

Establishes the ramp is per-element, not just correctly shaped.
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Sylpheed port agent
2026-09-02 16:20:27 +00:00
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docs/port/splash-animation-fixed.md
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@@ -67,8 +67,94 @@ misreading it.
* That it **looks** right. Three instruments have now agreed with a picture a
human called wrong, and the fourth agreeing does not change the standing of
the fifth. A play-test is the check.
* Anything about the **developer** splash's three logo/companion pairs. One
element, one screen.
* ~~Anything about the **developer** splash's three logo/companion pairs. One
element, one screen.~~ ✅ **Closed below, and the developer splash turned out to
be the far better test.**
* The **absolute** alpha. The shape matches; whether the port's alpha equals the
game's at a given unit is `verify-capture`'s question, and it answers 0.01 %
at the settled pose only.
---
# ✅ The developer splash: three elements, TWO declared shapes, on one screen
The publisher check above had a structural weakness I named at the time: one
element, one screen, one shape. If the port applied *some* single ramp to
everything, that check would pass.
**The developer splash cannot be fooled that way, because it declares two
different shapes at once:**
| element | declared alpha | middle segment |
|---|---|---|
| `palogo_gamearts_eff` | `0:0 15:255 30:255 45:0` | **flat** |
| `palogo_seta_eff` | `0:0 15:255 30:255 45:0` | **flat** |
| `palogo_anima_eff` | `0:0 15:255 30:212 45:0` | **decays 17 %** |
Same screen, same frames, same clock, same code path. The two flat elements are
the control for the one that is not — no second run, no second renderer, and
nothing for a phase or rate error to hide behind, because any such error hits all
three identically.
## Pre-registered, before the film was read
> In units 15→30, `gamearts` and `seta` hold flat while `anima` falls gently.
> All three fall steeply 30→45.
## Measured, off a real filmed boot
Companion-only strips (each companion's rectangle minus the logo sitting inside
it), mean luma, `--film-interval=0.03`:
```
segment units 16-29 units 31-44
gamearts +0.00000 -0.00101
seta +0.00000 -0.00151
anima -0.00001 -0.00003
```
**The two flat ones are flat to five decimals. The decaying one decays.** And all
three fall over 31–44, so the flatness is not a dead element.
## The quantitative version, and the falsification arm
Each trace normalised by a **single solved gain** — one scalar per element, not a
per-point fit — against the declared curve, over the whole `t=0..45` ramp:
| element | fitted against | max err | rms err |
|---|---|---|---|
| `gamearts` | **its own (flat)** | **0.49 %** | 0.23 % |
| `seta` | **its own (flat)** | **0.50 %** | 0.27 % |
| `anima` | **its own (decay)** | **2.18 %** | 1.19 % |
| `gamearts` | anima's decay | 8.32 % | 4.80 % |
| `seta` | anima's decay | 8.08 % | 4.86 % |
| `anima` | flat | 8.82 % | 4.94 % |
**Both directions.** Every element fits its own declared shape 4–17× better than
it fits the other one available on the same screen. A port that drew one ramp for
all three would sit at ~8 % on at least one row; none does.
`anima`'s 2.18 % is the loosest row and the reason is its signal: its
companion-only strip means ~0.0005 against gamearts's ~0.015, thirty times
dimmer, so its noise floor is thirty times higher in these units. It still
separates from the wrong curve by 4×.
## What this adds over the publisher check
The publisher check established that the ramp has the declared *breakpoints and
slope ratios*. This establishes that the ramp is **per-element** — that the port
reads each element's own keyframes rather than applying a screen-wide curve. That
is a different failure mode, and it is the one that would have survived the
publisher check unnoticed.
## What it still does not establish
* That it **looks** right. This is instrument five. The standing of a human's
eyes is unchanged by it.
* The **absolute** alpha, for the same reason as above — a solved gain is
deliberately scale-free, so this is a shape result and says nothing about
whether the port's alpha equals the game's at a given unit.
* Anything about the **logo** elements. Both checks measure the pre-blurred
*companions*, because those are the strips that can be isolated from the sharp
logo underneath them.