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@@ -156,6 +156,141 @@ endsolid cube"""
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# If result is None, dependencies might not be fully functional
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# which is acceptable
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+ @pytest.mark.skipif(
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+ not _check_trimesh_available(),
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+ reason="trimesh not installed",
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+ )
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+ def test_generated_thumbnail_is_shaded_not_flat(self, distinct_surface_tones):
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+ """The render must be lit, not a flat silhouette (issue #2816).
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+
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+ Without ``shade=True`` every triangle is filled with BAMBU_GREEN
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+ regardless of its normal, so any model renders as its own outline and
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+ one file is indistinguishable from another in the File Manager.
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+ """
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+ import trimesh
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+
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+ from backend.app.services.stl_thumbnail import generate_stl_thumbnail
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+
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+ with tempfile.TemporaryDirectory() as tmpdir:
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+ stl_path = Path(tmpdir) / "cube.stl"
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+ trimesh.creation.box(extents=(10.0, 10.0, 10.0)).export(str(stl_path))
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+
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+ result = generate_stl_thumbnail(stl_path, Path(tmpdir))
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+ assert result is not None
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+
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+ # Three faces of a cube face the camera at the default isometric
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+ # view_init, and with the light on the camera's side each catches it
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+ # differently. This held at 3 before only because ``alpha=0.9`` let a
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+ # back face bleed through two IDENTICALLY lit front faces — re-render
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+ # at alpha=1.0 then and the count fell to 2. It is shading now.
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+ assert distinct_surface_tones(Path(result).read_bytes()) >= 3
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+
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+ @pytest.mark.skipif(
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+ not _check_trimesh_available(),
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+ reason="trimesh not installed",
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+ )
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+ @pytest.mark.parametrize(
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+ ("label", "punch_holes"),
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+ [("watertight", False), ("open", True)],
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+ )
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+ def test_backwards_wound_triangles_render_the_same(self, label, punch_holes):
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+ """Vertex ORDER must not change the picture.
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+
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+ matplotlib takes its normals from winding, so an inverted triangle shades
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+ as though it faced away — the model comes out patchy, like camouflage.
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+ Unshaded this was invisible, which makes it a regression the shading
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+ introduced rather than one it revealed, and the File Manager accepts
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+ whatever STL a user uploads.
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+
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+ Asserted as "same picture as the correctly wound mesh", because the
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+ obvious assertion does not work: broken winding produces MORE distinct
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+ tones, not fewer, so a tone count cannot see it.
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+
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+ Run BOTH watertight and open, because the two are repaired by different
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+ code. ``fix_inversion`` decides which way is out from the sign of the
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+ volume and gives up when the mesh is not watertight, which is the common
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+ shape of a broken STL — there, ``fix_winding`` settles inward unopposed
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+ and the centroid fallback in ``_repair_winding`` is the only thing
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+ holding this. Without it the open case renders at a mean delta of 4.56.
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+ """
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+ import numpy as np
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+ import trimesh
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+ from PIL import Image
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+
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+ from backend.app.services.stl_thumbnail import generate_stl_thumbnail
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+
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+ sphere = trimesh.creation.icosphere(subdivisions=3, radius=5.0)
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+ keep = sphere.faces.copy()[:-80] if punch_holes else sphere.faces.copy()
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+ good = trimesh.Trimesh(vertices=sphere.vertices.copy(), faces=keep.copy())
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+ assert good.is_watertight is not punch_holes, "fixture has the wrong topology"
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+
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+ faces = keep.copy()
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+ faces[::2] = faces[::2][:, ::-1]
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+ bad = trimesh.Trimesh(vertices=sphere.vertices.copy(), faces=faces)
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+ assert not bad.is_winding_consistent, "fixture is supposed to be broken"
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+
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+ with tempfile.TemporaryDirectory() as tmpdir:
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+ out = Path(tmpdir)
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+ rendered = []
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+ for name, mesh in (("good", good), ("bad", bad)):
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+ path = out / f"{name}.stl"
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+ mesh.export(str(path))
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+ result = generate_stl_thumbnail(path, out)
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+ assert result is not None
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+ rendered.append(np.asarray(Image.open(result).convert("RGB"), dtype=float))
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+
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+ assert rendered[0].shape == rendered[1].shape
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+ mean_delta = float(np.abs(rendered[0] - rendered[1]).mean())
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+
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+ # Repaired they are the same mesh, so this is ~0. Without the repair the
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+ # inverted half renders dark against the lit half and it is an order of
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+ # magnitude higher.
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+ assert mean_delta < 1.0, f"winding changed the {label} render (mean delta {mean_delta:.2f})"
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+
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+ @pytest.mark.skipif(
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+ not _check_trimesh_available(),
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+ reason="trimesh not installed",
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+ )
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+ def test_degenerate_mesh_still_renders(self):
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+ """A mesh with no shadeable face must render flat, not fail.
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+
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+ matplotlib's ``_shade_colors`` falls back to returning the colour it was
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+ given when every normal is degenerate, and for a colour STRING that is a
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+ 0-d array — ``to_rgba_array`` then raises ``TypeError: len() of unsized
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+ object``. So these files rendered fine while the output was flat, and
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+ turning the light on would have broken them.
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+
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+ They are not hypothetical: stub and truncated STLs reach here, and
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+ ``batch_generate_stl_thumbnails`` walks a whole folder with no
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+ minimum-size pre-skip, so each one would show as a failure in the UI.
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+ """
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+ import struct
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+
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+ from backend.app.services.stl_thumbnail import generate_stl_thumbnail
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+
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+ def write_binary_stl(path, triangles):
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+ # Written by hand rather than via trimesh.export, which drops
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+ # degenerate facets and would quietly defeat the test.
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+ with open(path, "wb") as fh:
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+ fh.write(b"\0" * 80)
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+ fh.write(struct.pack("<I", len(triangles)))
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+ for tri in triangles:
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+ fh.write(struct.pack("<3f", 0.0, 0.0, 0.0))
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+ for vertex in tri:
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+ fh.write(struct.pack("<3f", *vertex))
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+ fh.write(b"\0\0")
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+
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+ cases = {
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+ "zero_area": [[(0, 0, 0), (0, 0, 0), (0, 0, 0)]],
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+ "collinear": [[(0, 0, 0), (1, 1, 1), (2, 2, 2)]],
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+ }
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+ with tempfile.TemporaryDirectory() as tmpdir:
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+ out = Path(tmpdir)
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+ for name, triangles in cases.items():
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+ path = out / f"{name}.stl"
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+ write_binary_stl(path, triangles)
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+ assert generate_stl_thumbnail(path, out) is not None, f"{name} used to render and must still render"
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+
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def test_generate_stl_thumbnail_nonexistent_file(self):
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"""Test thumbnail generation with nonexistent file."""
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from backend.app.services.stl_thumbnail import generate_stl_thumbnail
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@@ -220,6 +355,51 @@ class TestStlThumbnailConstants:
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assert BAMBU_GREEN == "#00AE42"
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+ def test_light_gives_the_two_visible_faces_different_shades(self):
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+ """The whole point of lighting: adjacent visible faces must differ.
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+
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+ Both halves are asserted because neither alone is the property.
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+
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+ A positive dot product only says the light is not BEHIND the model, and
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+ that is not sufficient: azdeg=45 — "put the light where the camera is",
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+ the most natural next edit anyone would make — scores the HIGHEST dot
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+ product of any azimuth (+0.94) and lights both visible faces to the
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+ identical 0.825, which is a cube with no contrast down its front edge.
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+ The original bug (225) failed the other way, at -0.34.
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+
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+ Shade factors are matplotlib's own: ``Normalize(-1, 1)`` into
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+ ``Normalize(0.3, 1).inverse``, i.e. ``0.3 + 0.7 * (dot + 1) / 2``.
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+ """
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+ import numpy as np
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+ from matplotlib.colors import LightSource
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+
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+ from backend.app.services.stl_thumbnail import (
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+ LIGHT_ALTITUDE_DEG,
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+ LIGHT_AZIMUTH_DEG,
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+ VIEW_AZIM_DEG,
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+ VIEW_ELEV_DEG,
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+ )
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+
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+ elev, azim = np.radians(VIEW_ELEV_DEG), np.radians(VIEW_AZIM_DEG)
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+ camera = np.array([np.cos(elev) * np.cos(azim), np.cos(elev) * np.sin(azim), np.sin(elev)])
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+ light = LightSource(azdeg=LIGHT_AZIMUTH_DEG, altdeg=LIGHT_ALTITUDE_DEG).direction
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+
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+ assert float(light @ camera) > 0, "the light is behind the model"
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+
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+ def shade(normal):
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+ return 0.3 + 0.7 * ((float(np.array(normal) @ light) + 1) / 2)
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+
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+ # The two faces of an axis-aligned box that face the default camera.
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+ assert abs(shade([1, 0, 0]) - shade([0, 1, 0])) > 0.05, (
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+ "both visible faces are lit the same — the front edge disappears"
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+ )
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+
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+ def test_light_is_above_the_horizon(self):
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+ """Grazing or overhead both collapse the contrast the shading exists for."""
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+ from backend.app.services.stl_thumbnail import LIGHT_ALTITUDE_DEG
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+
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+ assert 0 < LIGHT_ALTITUDE_DEG < 90
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+
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def test_background_color(self):
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"""Test that background color is defined."""
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from backend.app.services.stl_thumbnail import BACKGROUND_COLOR
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Maksim Sadontsev