2f1c561d76
Answers the port s question, which they refused to guess at: they emit both a parent record and its nested leaf, each with an alpha ramp over a different span, and would not draw the leaf without the composition rule. The per-draw capture records vertex colours, and on the title s ptloop draw they are C3FFFFFF and B6FFFFFF -- alpha 195 and 182, not 255 -- so the composed alpha is observable. Fitting ONLY the two alphas against the two leaf ramps gives one consistent time, t = 355, where leaf A is 194.8 against an observed 195 and leaf B is 182.2 against 182. The parent has expired there: it returns to 0 at t=250 and a group holds at its last keyframe. So leaf times parent over 255 predicts zero for both quads and the sweeps would be invisible. They are drawn. The position check was predicted rather than fitted: nothing about x entered the fit, and the same t=355 places the quad centres at 981 and 478 against 992.0 and 467.2 measured off the capture -- within about 11 px on 400-px quads travelling 1560 and 1950 px. Four quantities from two differently-shaped ramps agree on one time. The rule: a leaf carrying geometry animates on its own timeline and the parent s alpha does not gate it. For these records the parent is a container with no sprite. Reach stated: one draw, one capture, one element pair, and specifically the case where the parent carries no geometry. The opposite case is already recorded -- for a button a base record s leaf duplicates the parent and the parent wins -- so the discriminator is which record carries the geometry, not a fixed precedence. And because every observation here has parent alpha 0, "the leaf wins" is not separated from "the parent is ignored because it draws nothing"; a capture during t=100 to 238 would separate them. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
57 lines
2.6 KiB
Rust
57 lines
2.6 KiB
Rust
//! How do a parent record's alpha ramp and its nested `.rat` leaf's compose?
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//!
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//! The port emits both but will not draw the leaf without knowing the rule --
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//! rightly, since drawing on a guess trades a visible 1.82 % error for an
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//! invisible wrong one. There is an oracle for this: the GPU draw capture
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//! records **vertex colours**, and on the title's `ptloop` draw they are
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//! `C3FFFFFF` and `B6FFFFFF` -- alpha **195** and **182**, not 255. So the game's
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//! composed alpha is observable, and a candidate rule either predicts those two
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//! numbers or does not.
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//!
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//! cargo run -p sylpheed-formats --example leaf_alpha_compose -- <GP_TITLE.pak>
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use sylpheed_formats::{pak, ui_layout};
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fn alpha_of(kf: &ui_layout::Keyframe) -> u32 {
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// The keyframe block's +0 is an ARGB fade colour; alpha is its high byte.
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kf.fade >> 24
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}
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fn main() {
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let path = std::env::args().nth(1).expect("usage: <pak>");
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let ar = pak::PakArchive::open(&path).expect("open");
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let e = &ar.entries()[4]; // GP_TITLE entry 4 = the English title
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let bytes = ar.read(e).expect("read");
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let build = ui_layout::parse_build(&bytes).expect("build");
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for name in ["ptloop01.rat", "ptloop02.rat"] {
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println!("\n=== {name} ===");
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if let Some(el) = build.elements.iter().find(|x| x.name == name) {
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println!(" PARENT keyframes (t, alpha, scale, rot, x,y):");
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for k in &el.keyframes {
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println!(" t={:<5} a={:<4} scale=({},{}) rot={:<5} ({},{})",
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k.time.map(|t| t as i64).unwrap_or(-1), alpha_of(k), k.scale_x, k.scale_y, k.rotation_deg, k.x, k.y);
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}
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}
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match build.records.get(name) {
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Some(&(off, size)) => {
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let leaf = &bytes[off..off + size];
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match ui_layout::parse_build(leaf) {
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Some(lb) => {
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for le in &lb.elements {
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println!(" LEAF element {:?}:", le.name);
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for k in &le.keyframes {
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println!(" t={:<5} a={:<4} scale=({},{}) rot={:<5} ({},{})",
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k.time.map(|t| t as i64).unwrap_or(-1), alpha_of(k), k.scale_x, k.scale_y,
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k.rotation_deg, k.x, k.y);
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}
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}
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}
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None => println!(" leaf did not parse"),
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}
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}
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None => println!(" no leaf record"),
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}
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}
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println!("\nOBSERVED in the draw capture: quad A alpha 195 (0xC3), quad B alpha 182 (0xB6)");
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}
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