Mesh Operations Tutorial¶

This tutorial covers common mesh operations in detail.

Loading Meshes¶

PyGEL3D supports several mesh formats:

import pygel3d.hmesh as hmesh

# Auto-detect format
m = hmesh.load("model.obj")

# Specific format loaders
m = hmesh.obj_load("model.obj")
m = hmesh.off_load("model.off")
m = hmesh.ply_load("model.ply")
m = hmesh.x3d_load("model.x3d")

Mesh Traversal¶

Iterating Over Elements¶

# Iterate over vertices
for v in m.vertices():
    pos = m.positions()[3*v:3*v+3]
    print(f"Vertex {v}: {pos}")

# Iterate over faces
for f in m.faces():
    print(f"Face {f}")

# Iterate over halfedges
for h in m.halfedges():
    print(f"Halfedge {h}")

Circulating Around Elements¶

# Circulate around a vertex
vertex_id = 0
neighbors = m.circulate_vertex(vertex_id, mode='v')
print(f"Neighbor vertices: {neighbors}")

# Circulate around a face
face_id = 0
vertices = m.circulate_face(face_id, mode='v')
print(f"Face vertices: {vertices}")

Mesh Repair¶

Stitching Coincident Vertices¶

# Merge vertices that are very close
threshold = 1e-6
num_merged = hmesh.stitch_mesh(m, threshold)
print(f"Merged {num_merged} vertex pairs")

Closing Holes¶

# Close holes up to 100 edges
max_hole_size = 100
hmesh.close_holes(m, max_hole_size)

Removing Degenerate Features¶

# Remove caps (nearly flat triangles at edges)
hmesh.remove_caps(m, threshold=0.1)

# Remove needles (very thin triangles)
hmesh.remove_needles(m, threshold=0.1, averagePositions=True)

Mesh Smoothing¶

Catmull-Clark Smoothing¶

# Apply CC smoothing (subdivides and smooths)
hmesh.cc_smooth(m)

Laplacian Smoothing¶

# Smooth with weight 0.5 for 10 iterations
hmesh.laplacian_smooth(m, w=0.5, no_iters=10)

Taubin Smoothing¶

# Better volume preservation
hmesh.taubin_smooth(m, no_iters=10)

Mesh Subdivision¶

Catmull-Clark¶

# Subdivide using Catmull-Clark scheme
hmesh.cc_split(m)

Loop Subdivision¶

# For triangle meshes
hmesh.loop_split(m)

Mesh Simplification¶

# Simplify to 50% of faces
hmesh.quadric_simplify(
    m,
    keep_fraction=0.5,
    singular_thresh=1e-10,
    error_thresh=1e10
)

Mesh Optimization¶

Edge Flipping¶

# Optimize valency (tries to make vertices degree 6)
hmesh.optimize_valency(m, anneal=True)

# Maximize minimum angle
hmesh.maximize_min_angle(m, thresh=0.1, anneal=True)

# Minimize curvature
hmesh.minimize_curvature(m, anneal=True)

See the API Reference for complete function documentation.