ship: diagnostics — baked-table renderer + evidence the placement IS static

ship_render example: assemble a ship from the baked capture table (or --static)
and write orthographic top/side PPM renders + per-part world bounds — the
offline eye for placement bugs.

Findings recorded (docs to follow with the fix):
- e106 baked eng_01 is CROSS-INSTANCE contamination: the F10 capture de-dups by
  vertex-buffer address alone, so for a part drawn by several fleet ships only
  the FIRST instance's transform survives; eng_01's 30-degree rotation and
  below-hull position belong to a different destroyer. Fleet formation made it
  reproduce across captures, defeating the cross-validation.
- The static composite DOES carry the exact placement: BE-f64 +-264.0 (the
  lateral hull pair offset the static assembler loses) and -164.044 (the bridge
  Z we captured as -164.037) sit in e_rou_e106's node joint tables. The static
  decode is incomplete, not the data — full static assembly is achievable, with
  captures demoted to a verification oracle.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/sylpheed-formats/examples/ship_render.rs

@@ -0,0 +1,125 @@
+//! Diagnostic: assemble a ship from the BAKED capture table (or the static
+//! scene graph with --static) and render orthographic PNGs + print per-part
+//! world bounds, to see exactly what the viewer shows.
+//!   cargo run --release --example ship_render -- <Stage_SNN.xpr path> <ship_id> <out_prefix> [--static]
+use std::collections::HashSet;
+use sylpheed_formats::mesh::{ScenePart, Xbg7Model};
+use sylpheed_formats::ship::assemble_ship;
+use sylpheed_formats::ship_capture::{embedded_placement, to_scene_parts};
+
+fn main() {
+    let a: Vec<String> = std::env::args().collect();
+    let use_static = a.iter().any(|s| s == "--static");
+    let (path, id, out) = (&a[1], &a[2], &a[3]);
+    let bytes = std::fs::read(path).unwrap();
+
+    let placed: Vec<ScenePart> = if use_static {
+        assemble_ship(&bytes, id, true)
+    } else {
+        let cap = embedded_placement(id).expect("ship not in baked table");
+        to_scene_parts(&cap)
+    };
+    let want: HashSet<String> = placed.iter().map(|p| p.resource.clone()).collect();
+    let models = Xbg7Model::models_named(&bytes, &want, &|| false);
+
+    // World triangles + per-part bounds.
+    let mut tris: Vec<[[f32; 3]; 3]> = Vec::new();
+    for p in &placed {
+        let Some(m) = models.iter().find(|m| m.name == p.resource) else { continue };
+        let mut lo = [f32::MAX; 3];
+        let mut hi = [f32::MIN; 3];
+        for sub in &m.meshes {
+            let w: Vec<[f32; 3]> = sub.positions.iter().map(|v| p.apply(*v)).collect();
+            for v in &w {
+                for k in 0..3 {
+                    lo[k] = lo[k].min(v[k]);
+                    hi[k] = hi[k].max(v[k]);
+                }
+            }
+            for t in sub.indices.chunks_exact(3) {
+                tris.push([w[t[0] as usize], w[t[1] as usize], w[t[2] as usize]]);
+            }
+        }
+        println!(
+            "{:20} X[{:8.1},{:8.1}] Y[{:8.1},{:8.1}] Z[{:8.1},{:8.1}]",
+            p.resource, lo[0], hi[0], lo[1], hi[1], lo[2], hi[2]
+        );
+    }
+    println!("total {} tris from {} placements", tris.len(), placed.len());
+
+    // Orthographic z-buffered flat renders: top (X/Z, look down −Y) and side (Z/Y, look down −X).
+    for (name, ax, ay, az) in [("top", 0usize, 2usize, 1usize), ("side", 2usize, 1usize, 0usize)] {
+        let size = 900usize;
+        let (mut lo, mut hi) = ([f32::MAX; 3], [f32::MIN; 3]);
+        for t in &tris {
+            for v in t {
+                for k in 0..3 {
+                    lo[k] = lo[k].min(v[k]);
+                    hi[k] = hi[k].max(v[k]);
+                }
+            }
+        }
+        let cx = (lo[ax] + hi[ax]) * 0.5;
+        let cy = (lo[ay] + hi[ay]) * 0.5;
+        let ext = (hi[ax] - lo[ax]).max(hi[ay] - lo[ay]) * 0.55;
+        let scale = (size as f32 * 0.5) / ext;
+        let mut img = vec![0u8; size * size * 3];
+        let mut zbuf = vec![f32::MIN; size * size];
+        for t in &tris {
+            // screen coords
+            let p: Vec<[f32; 3]> = t
+                .iter()
+                .map(|v| {
+                    [
+                        (v[ax] - cx) * scale + size as f32 * 0.5,
+                        (cy - v[ay]) * scale + size as f32 * 0.5,
+                        v[az],
+                    ]
+                })
+                .collect();
+            // flat shade by triangle normal Z-ish
+            let e1 = [t[1][0] - t[0][0], t[1][1] - t[0][1], t[1][2] - t[0][2]];
+            let e2 = [t[2][0] - t[0][0], t[2][1] - t[0][1], t[2][2] - t[0][2]];
+            let n = [
+                e1[1] * e2[2] - e1[2] * e2[1],
+                e1[2] * e2[0] - e1[0] * e2[2],
+                e1[0] * e2[1] - e1[1] * e2[0],
+            ];
+            let nl = (n[0] * n[0] + n[1] * n[1] + n[2] * n[2]).sqrt().max(1e-6);
+            let lum = (n[az].abs() / nl * 200.0 + 40.0) as u8;
+            // bbox raster
+            let minx = p.iter().map(|v| v[0]).fold(f32::MAX, f32::min).max(0.0) as usize;
+            let maxx = (p.iter().map(|v| v[0]).fold(f32::MIN, f32::max).min(size as f32 - 1.0)) as usize;
+            let miny = p.iter().map(|v| v[1]).fold(f32::MAX, f32::min).max(0.0) as usize;
+            let maxy = (p.iter().map(|v| v[1]).fold(f32::MIN, f32::max).min(size as f32 - 1.0)) as usize;
+            let det = (p[1][0] - p[0][0]) * (p[2][1] - p[0][1]) - (p[2][0] - p[0][0]) * (p[1][1] - p[0][1]);
+            if det.abs() < 1e-6 {
+                continue;
+            }
+            for y in miny..=maxy {
+                for x in minx..=maxx {
+                    let (fx, fy) = (x as f32 + 0.5, y as f32 + 0.5);
+                    let w0 = ((p[1][0] - fx) * (p[2][1] - fy) - (p[2][0] - fx) * (p[1][1] - fy)) / det;
+                    let w1 = ((p[2][0] - fx) * (p[0][1] - fy) - (p[0][0] - fx) * (p[2][1] - fy)) / det;
+                    let w2 = 1.0 - w0 - w1;
+                    if w0 < 0.0 || w1 < 0.0 || w2 < 0.0 {
+                        continue;
+                    }
+                    let z = w0 * p[0][2] + w1 * p[1][2] + w2 * p[2][2];
+                    let idx = y * size + x;
+                    if z > zbuf[idx] {
+                        zbuf[idx] = z;
+                        img[idx * 3] = lum;
+                        img[idx * 3 + 1] = lum;
+                        img[idx * 3 + 2] = lum;
+                    }
+                }
+            }
+        }
+        let file = format!("{out}_{name}.ppm");
+        let mut ppm = format!("P6\n{size} {size}\n255\n").into_bytes();
+        ppm.extend_from_slice(&img);
+        std::fs::write(&file, ppm).unwrap();
+        println!("wrote {file}");
+    }
+}