added point normal calculation

meshvis/__init__.py

@@ -8,3 +8,4 @@ except ImportError as error:
 from .context import *
 from .immediate import *
 from .indexed_attribute import UniformAttribute, PointAttribute, FaceAttribute, HalfEdgeAttribute
+from .mesh_helper import *

meshvis/mesh_helper.py

-from .indexed_attribute import FaceAttribute
+from .indexed_attribute import FaceAttribute, PointAttribute, resolve_attributes, stretch_vertices
 import numpy as np
 
-def cross(a, b):
-    c = [a[1]*b[2] - a[2]*b[1],
-         a[2]*b[0] - a[0]*b[2],
-         a[0]*b[1] - a[1]*b[0]]
 
-    return c
+def calculateNormalEdges(vertices, face_indices, normals, length):
+    resolved_normals = resolve_attributes(face_indices, [normals])[0]
+    vertices, face_indices = stretch_vertices(vertices, face_indices)
+
+    edge_vertices = []
+    edge_indices = []
+    for i, vert in enumerate(vertices):
+        
+        norm = np.array(resolved_normals[i])
+        vert = np.array(vert)
+
+        edge_vertices.append(vert)
+        edge_vertices.append(np.add(norm*length, vert))
+
+        edge_indices.append([i*2, i*2 + 1])
+
+    return edge_vertices, edge_indices
 
 def calculateFaceNormals(vertices, face_indices):
     values = []
@@ -22,4 +34,30 @@ def calculateFaceNormals(vertices, face_indices):
         norm = norm / np.linalg.norm(norm)
         values.append(norm)
 
-    return FaceAttribute(values)
\ No newline at end of file
+    return FaceAttribute(values)
+
+def calculatePointNormals(vertices, face_indices):
+    values = [(np.array([0.0, 0.0, 0.0]), 0)] * len(vertices)
+    for face in face_indices:
+        v1 = np.array(vertices[face[0]])
+        v2 = np.array(vertices[face[1]])
+        v3 = np.array(vertices[face[2]])
+        
+        v12 = np.subtract(v2, v1)
+        v13 = np.subtract(v3, v1)
+       
+        norm = np.cross(v12, v13)
+        
+
+        values[face[0]] = ( values[face[0]][0] + norm, values[face[0]][1] + 1)
+        values[face[1]] = ( values[face[1]][0] + norm, values[face[1]][1] + 1)
+        values[face[2]] = ( values[face[2]][0] + norm, values[face[2]][1] + 1)
+
+
+    result = []
+    for val in values:
+        norm = val[0]/val[1]
+        norm = norm / np.linalg.norm(norm)
+        result.append(norm)
+
+    return PointAttribute(result)
\ No newline at end of file

[Isaak Lim]

Try to avoid iterating over numpy arrays if possible. It's faster to work on them directly.

I would suggest splitting values into two arrays:

normals = np.zeros_like(vertices)
counts = np.zeros(vertices.shape[0])

and then you can do something similar to this:

normals /= counts.reshape(-1,1)
normals /= np.linalg.norm(normals, axis=1).reshape(-1,1)
return PointAttribute(normals)