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re: the black gap between screens is NOT a load -- measured, three legs

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sylpheed-port's BLOCKED ask #2. The gap was the one quantity in the transition
with no rule: measured at 0, 3 and 2 frames across three transitions, and I had
proposed it might be a load, which would make it emulator- and storage-dependent
and unauthorable.

Leg 1, bundle size runs the wrong way. If the gap were the incoming bundle
arriving, the biggest bundle would gap longest. Build 4 is 12 278 666 B and gaps
ZERO frames; build 5 is 6 977 437 B and gaps 3 and 2.

Leg 2, ran title->menu a second time from cold. The outgoing ramp is
byte-identical (63, 127, 191, 255) and the gap is 3 frames in BOTH runs.

Leg 3, and the two runs are not a null comparison -- which is the objection leg 2
invites. The captures refute it themselves: press-to-first-change differs by ~12
frames between them (~25 against ~10). Something in this transition really is
cache-sensitive and moved by 0.4 s, while the gap did not move at all. The
control comes from inside the measurement rather than from an assumption that
conditions differed.

So the gap is deterministic to the frame and not a load. It is also not constant
across transitions (0, 3, 2, 3) and not in the fade group -- the port reports 866
keyframes across 16 screens with 0 untimed. A deterministic game quantity with no
rule found; black_hold_units stays 0, and "not a load" must not become a reason
to author a constant.

The load proposal in screen-transitions.md is marked refuted rather than deleted.

Also fills in docs/game/navigation.md, which the standing brief asks me to keep
and which I had not touched while measuring four transitions: a player-side
section on what a screen change looks like, and three scripting traps -- that
`pkill -f xenia_canary` kills the shell that ran it (cost a launch today, and the
same trap is already in METHOD for pgrep), that screen_id.py reports `menu`
during the attract loop, and that it cannot tell EXTRAS from the main menu.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v
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sylph-decoder
2026-08-30 14:28:00 +00:00
parent 6afe0c4ab8
commit e803930e88
4 changed files with 192 additions and 18 deletions
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docs/game/navigation.md
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@@ -252,6 +252,36 @@ side the cursor is on before pressing Ⓐ.**
---
## 4b. What a screen change looks like ✅ measured, three of them
Every screen carries a full-screen black quad (`pteff00.prm`) that paints last.
A screen change is that quad ramping to opaque on the way out, and the **incoming**
screen's own copy of it starting opaque and clearing on the way in — so a
transition is two screens' quads, not one shared effect. The outgoing ramp's length
is on the disc and matches the game **three for three**; the black between them
does not, and is not a constant.
| you press | going | outgoing ramp | black between | incoming clears over |
|---|---|---|---|---|
| Ⓑ | main menu → title | 5 frames | **none — they cross-fade** | 8 frames |
| Ⓐ | title → main menu | 4 frames | ~3 frames | 5 frames |
| Ⓑ | EXTRAS → main menu | 5 frames | **2 frames, fully blank** | 5 frames |
⚠️ **Ⓑ is not "the cancel animation".** Ⓑ out of the main menu cross-fades — the
title is already drawing while the menu is still fading — while Ⓑ out of EXTRAS
goes properly black first. Same button, two different-looking moves, and if you are
scripting against "the screen goes black" one of them will not do it.
⚠️ **Ⓐ off the title is slow to start.** About 25 rendered frames (~0.8 s) pass
between a delivered press and anything changing on screen; the other two start
immediately. A script that presses and then looks 0.5 s later sees the title still
up and can conclude the press was dropped.
Timings are in *rendered frames* at ~30 Hz, from the emulator's own draw stream, so
they do not stretch when the emulator runs slow —
[`screen-transitions.md`](../re/screen-transitions.md) ·
[`data/fade-three-transitions.txt`](../re/data/fade-three-transitions.txt).
## 5. Flying
Not started, and the game teaches it better than we could: **play the in-game
@@ -277,3 +307,18 @@ Traps that read as bugs but are not, all measured ✅:
* **A trace consumer that exits stalls the emulator**, which also reads as a dead
pad.
* Cold boot is slow; ~25 s once the shader and code caches are warm.
* **`pkill -f xenia_canary` kills the shell that ran it**, because `-f` matches
the whole command line and your own `bash -c` contains the pattern. The script
dies before the emulator does, silently, with no output at all. Kill by process
**name**: `ps -o pid= -C xenia_canary | xargs -r kill -9`. (The same trap is in
`METHOD.md` for `pgrep` wait-loops; it cost another launch on 2026-08-30.)
* **`screen_id.py` reports `menu` during the attract loop.** Two boots on
2026-08-30 logged `menu` at t=106 s and t=418 s while the game was still in the
intro movie. A wait-loop that breaks on `menu` will act on the wrong screen; the
loops here break on `title` for that reason.
* **`screen_id.py` cannot tell EXTRAS from the main menu** — both are dark blue
`GP_TITLE` screens and it answers `menu` for either. Use
[`which_title_screen.py`](../../tools/re-capture/which_title_screen.py), which
separates them by ~11 RMSE against ~18 within-class, and read the **margin**: a
margin under ~1 means "neither", which is what you get on a screen outside
`GP_TITLE` entirely.