feat(manifest): add Manifest.coverage_summary()

src/multicam_sim/manifest.py

@@ -391,6 +391,40 @@ def to_json(self) -> str:
         optional fields omitted, full float precision, strict (finite) JSON."""
         return self.model_dump_json(indent=2, exclude_none=True)
 
+    def coverage_summary(self) -> dict[int, tuple[float, float]]:
+        """Per-camera coverage across all (entity, frame, point) observations.
+
+        Maps each camera id to ``(visible_fraction, mean_occ_frac)``:
+
+        - ``visible_fraction`` — fraction of that camera's observations with
+          ``visible == True``, in ``[0, 1]`` (``0.0`` if it has no observations).
+        - ``mean_occ_frac`` — mean of the non-``None`` ``occ_frac`` values
+          (``0.0`` when none are recorded).
+
+        Pure read-only aggregation; numpy-free.
+        """
+        counts: dict[int, int] = {}
+        visible_counts: dict[int, int] = {}
+        occ_sums: dict[int, float] = {}
+        occ_counts: dict[int, int] = {}
+        for entity in self.entities:
+            for frame in entity.frames:
+                for point in frame.points.values():
+                    for obs in point.per_cam:
+                        counts[obs.cam] = counts.get(obs.cam, 0) + 1
+                        if obs.visible:
+                            visible_counts[obs.cam] = visible_counts.get(obs.cam, 0) + 1
+                        if obs.occ_frac is not None:
+                            occ_sums[obs.cam] = occ_sums.get(obs.cam, 0.0) + obs.occ_frac
+                            occ_counts[obs.cam] = occ_counts.get(obs.cam, 0) + 1
+        summary: dict[int, tuple[float, float]] = {}
+        for cam, total in counts.items():
+            visible_fraction = visible_counts.get(cam, 0) / total
+            occ_n = occ_counts.get(cam, 0)
+            mean_occ = occ_sums.get(cam, 0.0) / occ_n if occ_n else 0.0
+            summary[cam] = (visible_fraction, mean_occ)
+        return summary
+
 
 # --------------------------------------------------------------------------- #
 # Compute (pure projection + boolean visibility; no renderer).

tests/test_manifest.py

@@ -111,3 +111,30 @@ def test_no_occluders_occ_frac_is_zero() -> None:
     camera = scene.cameras[0]
     point = np.array([0.0, 0.0, 0.5], dtype=np.float64)
     assert occlusion_fraction(camera, point, [], sample_count=27, jitter=0.05) == 0.0
+
+
+def test_coverage_summary_flags_the_occluded_camera() -> None:
+    manifest = build_manifest(build_smoke_scene())
+    summary = manifest.coverage_summary()
+
+    # One entry per camera in the manifest.
+    assert set(summary) == {cam.id for cam in manifest.cameras}
+
+    # All visible fractions are in [0, 1].
+    for visible_fraction, mean_occ in summary.values():
+        assert 0.0 <= visible_fraction <= 1.0
+        assert mean_occ >= 0.0
+
+    # The most-occluded camera (highest mean occ_frac) has the lowest visible
+    # fraction — the whole point of the summary.
+    most_occluded = max(summary, key=lambda cam: summary[cam][1])
+    lowest_visible = min(summary, key=lambda cam: summary[cam][0])
+    assert most_occluded == lowest_visible
+
+
+def test_coverage_summary_mean_occ_ignores_none() -> None:
+    # Without object_radius the silhouette labels are None, but occ_frac is
+    # always recorded, so mean_occ_frac is a real average, never NaN.
+    manifest = build_manifest(build_smoke_scene())
+    for _visible_fraction, mean_occ in manifest.coverage_summary().values():
+        assert mean_occ == mean_occ  # not NaN