Add smoothing option for mesh2

.gitignore

@@ -20,3 +20,6 @@ stl2pdf
 stl2pov
 stlinfo
 *.inc
+
+# for pycharm IDE
+.idea/

stl2pov.py

@@ -92,13 +92,14 @@ def mesh1(name, vertices):
     return "\n".join(lines)
 
 
-def mesh2(name, vertices):
+def mesh2(name, vertices, corner_normals):
     """
     Create a POV-ray mesh2 object from facet data.
 
     Arguments:
         name: The name of the object.
         vertices: An (N,3) numpy array containing the vertex data.
+        corner_normals: An (N,3) array containing the vertex normal vectors.
 
     Returns:
         A string representation of a POV-ray mesh2 object.
@@ -113,6 +114,9 @@ def mesh2(name, vertices):
     # the STL coordinate system and that used in POV-ray
     lines += [f"    <{p[0]}, {p[2]}, {p[1]}>," for p in points]
     lines[-1] = lines[-1][:-1]
+    if len(corner_normals) > 0:
+        lines += ["  }\n  normal_vectors {", "    {},".format(len(corner_normals))]
+        lines += [f"    <{v[0]}, {v[2]}, {v[1]}>," for v in corner_normals]
     lines += ["  }\n  face_indices {", f"    {len(ifacets)},"]
     lines += [f"    <{f[0]}, {f[1]}, {f[2]}>," for f in ifacets]
     lines[-1] = lines[-1][:-1]
@@ -138,6 +142,7 @@ def main(argv):
         default="utf-8",
     )
     parser.add_argument("-v", "--version", action="version", version=__version__)
+    parser.add_argument("-s", "--smooth", action="store_true", help="add smoothing normals")
     parser.add_argument(
         "--log",
         default="warning",
@@ -174,9 +179,13 @@ def main(argv):
         outs = f"// Generated by stl2pov {__version__}\n"
         outs += f"// on {time.asctime()}.\n"
         outs += f'// Source file name: "{fn}"\n'
+        corner_normals = (())
+        if args.smooth:
+            logging.info("generating corner normals.")
+            corner_normals = stl.corner_normals(vertices)
         if args.mesh2:
             logging.info("generating mesh2 data.")
-            outs += mesh2(name, vertices)
+            outs += mesh2(name, vertices, corner_normals)
         else:
             logging.info("generating mesh data.")
             outs += mesh1(name, vertices)

stltools/stl.py

@@ -177,6 +177,30 @@ def normals(facets, points):
     return vo.indexate(nv)
 
 
+def corner_normals(vertices):
+    """
+    Calculate corner normals for each shared vertex.
+
+    Arguments:
+        vertices: An (?,3) array containing the vertex data.
+
+    Returns:
+        a (?,3) array containing the corner normals
+    """
+    facets, points = toindexed(vertices)
+    facet_normal_indices, facet_normal_vectors = normals(facets, points)
+
+    # array of empty normal vectors at each vertex
+    corner_normal_sum = [[0 for i in range(len(points[0]))] for j in range(len(points))]
+    for facet in range(len(facets)):
+        for i in range(3):
+            vertex = facets[facet][i]
+            facet_normal_index = facet_normal_indices[facet]
+            for j in range(3):
+                corner_normal_sum[vertex][j] += facet_normal_vectors[facet_normal_index][j]
+    return [vo.normalize(v) for v in corner_normal_sum]
+
+
 def text(name, ifacets, points, inormals, vectors):
     """
     Make an STL text representation of a brep.