re: the capture is Stage_S02 -- provenance corrected, oracle grows to 46 buffers

capture_truth_scan places every drawn buffer across all 166 containers by modal
vbase-offset. Stage_S02 wins with 64 matches at one constant against Stage_S01's
16, and the logs carry f101/f105/f106/e105 -- a Stage-02 cast. Stage_S01 looked
consistent because the shared block is duplicated verbatim (twins 0x116F0 apart
in both), so the earlier structural findings hold; only the loaded-container
claim was wrong. The S02 table places 46 buffers, 12 claimed by nobody, and
resolves the six Stage_S01 mystery buffers as e105 parts.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/sylpheed-formats/examples/capture_truth_scan.rs

@@ -0,0 +1,112 @@
+//! Which container did each captured draw come from, and where in it?
+//!
+//! Extends the single-container `--map` check in `shared_vbase_check` to a whole
+//! `resource3d` directory. For each container it indexes every 4-byte-aligned
+//! position triple, looks up each draw's first dumped position, confirms the run
+//! at a fixed stride, and reports the modal `vbase − offset`. A container the
+//! engine loaded shows one dominant constant; an unrelated one shows noise.
+//!
+//! The output is capture-named ground truth for anchors far beyond the one ship
+//! `Stage_S01` gave us.
+//!
+//! Usage: capture_truth_scan <resource3d_dir> <capture.log>...
+use sylpheed_formats::ship_capture::{parse_capture, parse_drawlog, CapturedDraw};
+use std::collections::HashMap;
+
+fn q(v: f32) -> i64 {
+    (v as f64 * 1e4).round() as i64
+}
+
+fn main() {
+    let a: Vec<String> = std::env::args().collect();
+    let dir = &a[1];
+    let mut draws: Vec<CapturedDraw> = Vec::new();
+    let mut seen = std::collections::HashSet::new();
+    for log in &a[2..] {
+        let text = std::fs::read_to_string(log).expect("log");
+        let mut d = parse_capture(&text);
+        if d.is_empty() {
+            d = parse_drawlog(&text);
+        }
+        for x in d {
+            // One entry per buffer; the logs are already deduped per transform.
+            if x.pos.len() >= 8 && x.vcount >= 20 && seen.insert((log.clone(), x.vbase)) {
+                draws.push(x);
+            }
+        }
+    }
+    eprintln!("{} distinct (log, vbase) draws to place", draws.len());
+
+    let mut files: Vec<_> = std::fs::read_dir(dir)
+        .unwrap()
+        .flatten()
+        .map(|e| e.path())
+        .filter(|p| p.extension().and_then(|s| s.to_str()) == Some("xpr"))
+        .collect();
+    files.sort();
+
+    let mut placed = 0usize;
+    for f in &files {
+        let Ok(bytes) = std::fs::read(f) else { continue };
+        // Index quantised position triples. Junk floats (NaN/huge) are skipped,
+        // which prunes most of a texture-heavy container.
+        let be = |at: usize| f32::from_be_bytes(bytes[at..at + 4].try_into().unwrap());
+        let mut index: HashMap<(i64, i64, i64), Vec<u32>> = HashMap::new();
+        let mut o = 0usize;
+        while o + 12 <= bytes.len() {
+            let (x, y, z) = (be(o), be(o + 4), be(o + 8));
+            if x.is_finite() && y.is_finite() && z.is_finite() && x.abs() < 1e6 && y.abs() < 1e6 && z.abs() < 1e6
+            {
+                index.entry((q(x), q(y), q(z))).or_default().push(o as u32);
+            }
+            o += 4;
+        }
+        let mut deltas: HashMap<i64, Vec<(u32, u32)>> = HashMap::new();
+        for d in &draws {
+            let k = (q(d.pos[0][0]), q(d.pos[0][1]), q(d.pos[0][2]));
+            // ±1 in each axis: the log rounds, our file value may round the
+            // other way at a tie.
+            for dx in -1..=1i64 {
+                for dy in -1..=1i64 {
+                    for dz in -1..=1i64 {
+                        let Some(cands) = index.get(&(k.0 + dx, k.1 + dy, k.2 + dz)) else {
+                            continue;
+                        };
+                        for &off in cands {
+                            for stride in (12..=64).step_by(4) {
+                                let ok = (1..4).all(|j| {
+                                    let at = off as usize + j * stride;
+                                    at + 12 <= bytes.len()
+                                        && (0..3).all(|c| {
+                                            (be(at + c * 4) - d.pos[j][c]).abs() <= 1e-4
+                                        })
+                                });
+                                if ok {
+                                    deltas
+                                        .entry(d.vbase as i64 - off as i64)
+                                        .or_default()
+                                        .push((d.vbase, d.vcount));
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        let mut top: Vec<_> = deltas.into_iter().collect();
+        top.sort_by_key(|(_, v)| std::cmp::Reverse(v.len()));
+        if let Some((delta, hits)) = top.first() {
+            if hits.len() >= 3 {
+                placed += hits.len();
+                println!(
+                    "{:<22} base=0x{:<10X} buffers={}",
+                    f.file_name().unwrap().to_string_lossy(),
+                    delta,
+                    hits.len()
+                );
+            }
+        }
+    }
+    eprintln!("{placed} draws placed in a container");
+}