feat(P3): add GMSH Frontal-Delaunay tessellation engine
Introduces GMSH as an alternative to OCC BRepMesh for STEP→GLB tessellation. GMSH produces conforming meshes that eliminate fan triangles at cylinder seam edges — a structural limitation of OCC BRepMesh that cannot be fixed via deflection parameters. Changes: - render-worker/Dockerfile: install gmsh>=4.15.0 + libglu1-mesa + libxft2 - export_step_to_gltf.py: --tessellation_engine occ|gmsh CLI arg + _tessellate_with_gmsh() using BRep→GMSH→Poly_Triangulation write-back - admin.py: tessellation_engine setting (SETTINGS_DEFAULTS, SettingsOut, SettingsUpdate, validation) - export_glb.py: pass tessellation_engine to export_step_to_gltf.py CLI in both geometry and production GLB tasks - Admin.tsx: radio button UI for OCC vs GMSH selection Tested: 121 faces meshed, 0 BRepMesh fallback, 649K triangles on sample part. Clean seam edges for UV unwrap — GMSH respects B-rep periodic face boundaries. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
@@ -1,8 +1,8 @@
|
||||
"""OCC-native STEP → GLB export script.
|
||||
|
||||
Reads a STEP file via OCP/XCAF (preserving part names and embedded colors),
|
||||
tessellates with BRepMesh, optionally applies per-part hex colors, and writes
|
||||
a binary GLB in meters (Y-up, glTF convention).
|
||||
tessellates with BRepMesh or GMSH Frontal-Delaunay, optionally applies
|
||||
per-part hex colors, and writes a binary GLB in meters (Y-up, glTF convention).
|
||||
|
||||
No Blender required. Uses the same OCP bindings that cadquery ships with.
|
||||
|
||||
@@ -12,6 +12,7 @@ Usage:
|
||||
--output_path /path/to/output.glb \
|
||||
[--linear_deflection 0.1] \
|
||||
[--angular_deflection 0.5] \
|
||||
[--tessellation_engine occ|gmsh] \
|
||||
[--color_map '{"RingInner": "#4C9BE8", "RingOuter": "#E85B4C"}']
|
||||
|
||||
Exit 0 on success, exit 1 on failure.
|
||||
@@ -50,6 +51,10 @@ def parse_args() -> argparse.Namespace:
|
||||
"--sharp_threshold", type=float, default=20.0,
|
||||
help="Dihedral angle threshold (degrees) for sharp B-rep edge detection. Default 20.0",
|
||||
)
|
||||
parser.add_argument(
|
||||
"--tessellation_engine", choices=["occ", "gmsh"], default="occ",
|
||||
help="Tessellation backend: 'occ' = BRepMesh (default), 'gmsh' = Frontal-Delaunay",
|
||||
)
|
||||
return parser.parse_args()
|
||||
|
||||
|
||||
@@ -259,6 +264,169 @@ def _extract_sharp_edge_pairs(shape, sharp_threshold_deg: float = 20.0) -> list:
|
||||
return sharp_pairs
|
||||
|
||||
|
||||
def _tessellate_with_gmsh(shape, linear_deflection: float, angular_deflection: float) -> None:
|
||||
"""Tessellate an OCC TopoDS_Shape using GMSH Frontal-Delaunay mesher.
|
||||
|
||||
Writes the resulting Poly_Triangulation back to each TopoDS_Face via
|
||||
BRep_Builder.UpdateFace(), so the shape's tessellation data is available
|
||||
to RWGltf_CafWriter exactly like BRepMesh output.
|
||||
|
||||
GMSH surface tags correspond 1:1 to faces in TopExp_Explorer(FACE) order
|
||||
after importShapes() from a .brep file — no coordinate-based matching needed.
|
||||
|
||||
Falls back silently to BRepMesh for any face that GMSH cannot mesh (degenerate
|
||||
geometry, e.g. degenerate poles).
|
||||
|
||||
Args:
|
||||
shape: tessellated in-place (OCC TopoDS_Shape)
|
||||
linear_deflection: controls CharacteristicLengthMax (mm)
|
||||
angular_deflection: controls minimum circle subdivision points (rad)
|
||||
"""
|
||||
import math as _math
|
||||
import tempfile
|
||||
import gmsh
|
||||
|
||||
from OCP.BRep import BRep_Builder
|
||||
from OCP.BRepTools import BRepTools
|
||||
from OCP.BRepMesh import BRepMesh_IncrementalMesh
|
||||
from OCP.Poly import Poly_Triangulation, Poly_Array1OfTriangle, Poly_Triangle
|
||||
from OCP.TColgp import TColgp_Array1OfPnt
|
||||
from OCP.TopExp import TopExp_Explorer
|
||||
from OCP.TopAbs import TopAbs_FACE
|
||||
from OCP.TopoDS import TopoDS as _TopoDS
|
||||
from OCP.gp import gp_Pnt
|
||||
|
||||
# Write shape to temporary .brep for GMSH import
|
||||
with tempfile.NamedTemporaryFile(suffix=".brep", delete=False) as tmp:
|
||||
brep_path = tmp.name
|
||||
|
||||
n_faces_gmsh = 0
|
||||
n_faces_fallback = 0
|
||||
n_triangles_total = 0
|
||||
|
||||
try:
|
||||
BRepTools.Write_s(shape, brep_path)
|
||||
|
||||
gmsh.initialize()
|
||||
gmsh.option.setNumber("General.Terminal", 0) # suppress console output
|
||||
gmsh.option.setNumber("Mesh.Algorithm", 6) # Frontal-Delaunay 2D
|
||||
gmsh.option.setNumber("Mesh.RecombineAll", 0) # keep triangles (no quads)
|
||||
# CharacteristicLength controls edge length target in mm
|
||||
gmsh.option.setNumber("Mesh.CharacteristicLengthMin", linear_deflection * 0.5)
|
||||
gmsh.option.setNumber("Mesh.CharacteristicLengthMax", linear_deflection * 3.0)
|
||||
# Angular resolution via circle point count: 2π / angular_deflection
|
||||
min_circle_pts = max(6, int(_math.ceil(2.0 * _math.pi / max(angular_deflection, 0.01))))
|
||||
gmsh.option.setNumber("Mesh.MinimumCirclePoints", min_circle_pts)
|
||||
gmsh.option.setNumber("Mesh.MinimumCurvePoints", 3)
|
||||
# Reduce noise from GMSH warnings
|
||||
gmsh.option.setNumber("General.Verbosity", 1)
|
||||
|
||||
gmsh.model.add("shape")
|
||||
gmsh.model.occ.importShapes(brep_path)
|
||||
gmsh.model.occ.synchronize()
|
||||
gmsh.model.mesh.generate(2)
|
||||
|
||||
# Build lookup: surface tag → list of (node_coords, triangle_node_tags)
|
||||
# GMSH surface tags from importShapes correspond 1:1 to TopExp_Explorer(FACE) order
|
||||
surface_tags = [tag for (_, tag) in gmsh.model.getEntities(2)]
|
||||
|
||||
# Collect per-surface mesh data
|
||||
surface_mesh: dict[int, tuple] = {} # tag → (nodes_xyz, triangles)
|
||||
for stag in surface_tags:
|
||||
try:
|
||||
node_tags, coords, _ = gmsh.model.mesh.getNodes(dim=2, tag=stag, includeBoundary=True)
|
||||
if len(node_tags) == 0:
|
||||
continue
|
||||
# coords is flat [x0,y0,z0, x1,y1,z1, ...]
|
||||
node_map = {} # gmsh tag → 1-based local index
|
||||
pts_xyz = []
|
||||
for i, ntag in enumerate(node_tags):
|
||||
x, y, z = coords[3*i], coords[3*i+1], coords[3*i+2]
|
||||
node_map[ntag] = i + 1 # 1-based
|
||||
pts_xyz.append((x, y, z))
|
||||
|
||||
elem_types, elem_tags, elem_node_tags = gmsh.model.mesh.getElements(dim=2, tag=stag)
|
||||
tris = []
|
||||
for etype, etags, entags in zip(elem_types, elem_tags, elem_node_tags):
|
||||
if etype != 2: # type 2 = triangle
|
||||
continue
|
||||
n_elems = len(etags)
|
||||
for k in range(n_elems):
|
||||
a = node_map.get(entags[3*k])
|
||||
b = node_map.get(entags[3*k+1])
|
||||
c = node_map.get(entags[3*k+2])
|
||||
if a and b and c:
|
||||
tris.append((a, b, c))
|
||||
|
||||
if pts_xyz and tris:
|
||||
surface_mesh[stag] = (pts_xyz, tris)
|
||||
except Exception:
|
||||
continue
|
||||
|
||||
except Exception as _gmsh_err:
|
||||
print(f"WARNING: GMSH failed ({_gmsh_err}), falling back to BRepMesh", file=sys.stderr)
|
||||
# Fallback: full BRepMesh on the whole shape
|
||||
BRepMesh_IncrementalMesh(shape, linear_deflection, False, angular_deflection, True)
|
||||
return
|
||||
finally:
|
||||
try:
|
||||
gmsh.finalize()
|
||||
except Exception:
|
||||
pass
|
||||
try:
|
||||
Path(brep_path).unlink(missing_ok=True)
|
||||
except Exception:
|
||||
pass
|
||||
|
||||
# Map GMSH surface data back to OCC faces via TopExp_Explorer (same order as importShapes)
|
||||
builder = BRep_Builder()
|
||||
explorer = TopExp_Explorer(shape, TopAbs_FACE)
|
||||
face_index = 0 # 0-based → maps to surface_tags[face_index]
|
||||
|
||||
while explorer.More():
|
||||
face = _TopoDS.Face_s(explorer.Current())
|
||||
if face_index < len(surface_tags):
|
||||
stag = surface_tags[face_index]
|
||||
mesh_data = surface_mesh.get(stag)
|
||||
if mesh_data:
|
||||
pts_xyz, tris = mesh_data
|
||||
n_nodes = len(pts_xyz)
|
||||
n_tris = len(tris)
|
||||
try:
|
||||
arr_pts = TColgp_Array1OfPnt(1, n_nodes)
|
||||
for idx, (x, y, z) in enumerate(pts_xyz, 1):
|
||||
arr_pts.SetValue(idx, gp_Pnt(x, y, z))
|
||||
|
||||
arr_tris = Poly_Array1OfTriangle(1, n_tris)
|
||||
for idx, (a, b, c) in enumerate(tris, 1):
|
||||
arr_tris.SetValue(idx, Poly_Triangle(a, b, c))
|
||||
|
||||
tri = Poly_Triangulation(arr_pts, arr_tris)
|
||||
builder.UpdateFace(face, tri)
|
||||
n_faces_gmsh += 1
|
||||
n_triangles_total += n_tris
|
||||
except Exception as _e:
|
||||
# Fallback for this face only
|
||||
BRepMesh_IncrementalMesh(face, linear_deflection, False, angular_deflection, False)
|
||||
n_faces_fallback += 1
|
||||
else:
|
||||
# No GMSH mesh for this surface → BRepMesh fallback for this face
|
||||
BRepMesh_IncrementalMesh(face, linear_deflection, False, angular_deflection, False)
|
||||
n_faces_fallback += 1
|
||||
else:
|
||||
BRepMesh_IncrementalMesh(face, linear_deflection, False, angular_deflection, False)
|
||||
n_faces_fallback += 1
|
||||
|
||||
face_index += 1
|
||||
explorer.Next()
|
||||
|
||||
print(
|
||||
f"GMSH tessellation: {n_faces_gmsh} faces meshed, "
|
||||
f"{n_faces_fallback} BRepMesh fallback, "
|
||||
f"{n_triangles_total} triangles total"
|
||||
)
|
||||
|
||||
|
||||
def _inject_glb_extras(glb_path: Path, extras: dict) -> None:
|
||||
"""Patch a GLB binary to add/update scenes[0].extras JSON field.
|
||||
|
||||
@@ -337,16 +505,20 @@ def main() -> None:
|
||||
print(f"Found {free_labels.Length()} root shape(s), tessellating "
|
||||
f"(linear={args.linear_deflection}mm, angular={args.angular_deflection}rad) …")
|
||||
|
||||
engine = getattr(args, "tessellation_engine", "occ")
|
||||
for i in range(1, free_labels.Length() + 1):
|
||||
shape = shape_tool.GetShape_s(free_labels.Value(i))
|
||||
if not shape.IsNull():
|
||||
BRepMesh_IncrementalMesh(
|
||||
shape,
|
||||
args.linear_deflection,
|
||||
False, # isRelative
|
||||
args.angular_deflection,
|
||||
True, # isInParallel
|
||||
)
|
||||
if engine == "gmsh":
|
||||
_tessellate_with_gmsh(shape, args.linear_deflection, args.angular_deflection)
|
||||
else:
|
||||
BRepMesh_IncrementalMesh(
|
||||
shape,
|
||||
args.linear_deflection,
|
||||
False, # isRelative
|
||||
args.angular_deflection,
|
||||
True, # isInParallel
|
||||
)
|
||||
|
||||
# --- Extract sharp B-rep edge pairs (before mm→m scaling so coords are in mm) ---
|
||||
# Collect all free shapes into one list for the extraction function.
|
||||
|
||||
Reference in New Issue
Block a user