Feat: Add single-frame observer coordinate time option

tests/test_camera_cli.py

@@ -115,14 +115,15 @@ def map_vertices(path):
     return values, data[offset:offset + triangles * MAP_TRIANGLE_SIZE]
 
 
-with tempfile.TemporaryDirectory(prefix='gr-camera-cli-') as directory:
+with tempfile.TemporaryDirectory(prefix='gr-camera-cli-', dir='/tmp/opencode') as directory:
     tmp = Path(directory)
     for backend in ('minkowski', 'schwarzschild'):
         binary = BUILD / f'{backend}_sky'
         help_text = run(binary, '--help').stdout
         ext = 'png' if '.png' in help_text else 'ppm'
-        hdr_available = '--hdr-output' in help_text
-        for option in ('--observer-position', '--observer-velocity', '--camera-roll-deg'):
+        hdr_available = any(line.startswith('  --hdr-output ')
+                            for line in help_text.splitlines())
+        for option in ('--observer-time', '--observer-position', '--observer-velocity', '--camera-roll-deg'):
             assert option in help_text
         assert '--tone-map' in help_text and '--tone-map-p' in help_text
         assert '--sensor-bloom-limit' in help_text
@@ -162,6 +163,15 @@ with tempfile.TemporaryDirectory(prefix='gr-camera-cli-') as directory:
         assert pole == render('pole_explicit', '--observer-position', 0, 0, 30,
                               '--look-ra-deg', 0, '--look-dec-deg', -90)
         default = render('default')
+        # Stationary backends are time-translation invariant; the event time
+        # must nevertheless survive in lens-map metadata, including negatives.
+        for time in (0, 12.5, -12.5):
+            timed_map = tmp / f'{backend}_time_{time}.grlens'
+            assert default == render('timed', '--observer-time', time,
+                                     '--lens-map-output', timed_map)
+            saved_time, proper_time = struct.unpack_from(
+                '<dd', timed_map.read_bytes(), MAP_FRAME_HEADER_START + 8)
+            assert saved_time == time and proper_time == 0
         pos = (0, 0, 0) if backend == 'minkowski' else (0, 0, 30)
         assert default == render('default_explicit', '--observer-position', *pos,
                                  '--look-ra-deg', 90, '--look-dec-deg', -90)
@@ -221,6 +231,15 @@ with tempfile.TemporaryDirectory(prefix='gr-camera-cli-') as directory:
         assert 'PSF cache ready' not in too_long.stderr
 
         errors = [
+            (['--observer-time'], None),
+            (['--observer-time', ''], None),
+            (['--observer-time', 'bad'], None),
+            (['--observer-time', 'nan'], None),
+            (['--observer-time', 'inf'], None),
+            (['--observer-time', '-inf'], None),
+            (['--observer-track', 'missing.csv', '--observer-time', 0], 'cannot be combined'),
+            (['--frames-dir', tmp, '--observer-time', 0], 'cannot be combined'),
+            (['--lens-map-input', 'missing.grlens', '--observer-time', 0], 'cannot be combined'),
             (['--observer-position', 1, 2], None),
             (['--observer-position', 1, 2, 'nan'], None),
             (['--observer-velocity', 0, 0, 'inf'], None),
@@ -443,3 +462,30 @@ with tempfile.TemporaryDirectory(prefix='gr-camera-cli-') as directory:
                     f'movie lens map changed with {threads} threads'
             print('schwarzschild: movie lens map identical with 1, 4 and 16 threads', flush=True)
         print(f'{backend}: CLI checks passed; single/movie image identical, map max error {max_error:.3g}', flush=True)
+
+    # In the moving bubble, (t, x) -> (t+T, x+v_s*T) preserves the
+    # metric and physical ray endpoints. This detects a stale t=0 in either
+    # camera metric evaluation or ray initialization, not just map metadata.
+    alc = BUILD / 'alcubierre_sky'
+    if alc.exists():
+        reference = None
+        for time in (0, 12.5, -12.5):
+            path = tmp / f'alcubierre_time_{time}.grlens'
+            run(alc, *common, '--alcubierre-vs', 0.3,
+                '--alcubierre-radius', 1, '--observer-time', time,
+                '--observer-position', 0.3 * time, 0, 0,
+                '--observer-velocity', 0.3, 0, 0,
+                '--look-ra-deg', 0, '--look-dec-deg', 0,
+                '--lens-map-output', path, '--output', tmp / 'alcubierre.png')
+            assert struct.unpack_from('<d', path.read_bytes(),
+                                      MAP_FRAME_HEADER_START + 8)[0] == time
+            vertices, triangles = map_vertices(path)
+            if reference is None:
+                reference = vertices, triangles
+                continue
+            expected, expected_triangles = reference
+            assert len(vertices) == len(expected) and triangles == expected_triangles
+            for actual, baseline in zip(vertices, expected):
+                assert actual[9:12] == baseline[9:12]
+                assert max(abs(a - b) for a, b in zip(actual[:9], baseline[:9])) < 1e-8
+        print('alcubierre: nonzero camera-time translation checks passed', flush=True)