Add mesh smoothing reference

Author: constantinpape

development/utils/_mesh_smoothing_reference.py

@@ -0,0 +1,42 @@
+from typing import Tuple
+
+import nifty
+import numpy as np
+
+
+def smooth_mesh(
+    verts: np.ndarray, normals: np.ndarray, faces: np.ndarray, iterations: int
+) -> Tuple[np.ndarray, np.ndarray]:
+    """Smooth mesh surface via laplacian smoothing.
+
+    Args:
+        verts: The mesh vertices.
+        normals: The mesh normals.
+        faces: The mesh faces.
+        iterations: The number of smoothing iterations.
+
+    Returns:
+        The vertices after smoothing.
+        The normals after smoothing.
+    """
+    n_verts = len(verts)
+    g = nifty.graph.undirectedGraph(n_verts)
+
+    edges = np.concatenate([faces[:, :2], faces[:, 1:], faces[:, ::2]], axis=0)
+    g.insertEdges(edges)
+
+    current_verts = verts
+    current_normals = normals
+    new_verts = np.zeros_like(verts, dtype=verts.dtype)
+    new_normals = np.zeros_like(normals, dtype=normals.dtype)
+
+    # Implement this directly in nifty for speed up?
+    for it in range(iterations):
+        for vert in range(n_verts):
+            nbrs = np.array([vert] + [nbr[0] for nbr in g.nodeAdjacency(vert)], dtype="int")
+            new_verts[vert] = np.mean(current_verts[nbrs], axis=0)
+            new_normals[vert] = np.mean(current_normals[nbrs], axis=0)
+        current_verts = new_verts
+        current_normals = new_normals
+
+    return new_verts, new_normals