make "inner" edges more visible

yacv_server/plugin.py

@@ -0,0 +1 @@
+# TODO: Plugins that can freely modify the GLTF file as it is being built

yacv_server/tessellate.py

@@ -1,6 +1,7 @@
 import hashlib
 import io
 import re
+from typing import List, Dict, Tuple
 
 from OCP.BRep import BRep_Tool
 from OCP.BRepAdaptor import BRepAdaptor_Curve
@@ -9,7 +10,7 @@ from OCP.TopExp import TopExp
 from OCP.TopLoc import TopLoc_Location
 from OCP.TopTools import TopTools_IndexedMapOfShape
 from OCP.TopoDS import TopoDS_Face, TopoDS_Edge, TopoDS_Shape, TopoDS_Vertex
-from build123d import Shape, Vertex
+from build123d import Shape, Vertex, Face
 from pygltflib import GLTF2
 
 import mylogger
@@ -32,15 +33,23 @@ def tessellate(
     shape = Shape(ocp_shape)
 
     # Perform tessellation tasks
+    edge_to_faces: Dict[TopoDS_Edge, List[TopoDS_Face]] = {}
+    vertex_to_faces: Dict[TopoDS_Vertex, List[TopoDS_Face]] = {}
     if faces:
         for face in shape.faces():
             _tessellate_face(mgr, face.wrapped, tolerance, angular_tolerance)
+            if edges:
+                for edge in face.edges():
+                    edge_to_faces[edge] = edge_to_faces.get(edge, []) + [face.wrapped]
+            if vertices:
+                for vertex in face.vertices():
+                    vertex_to_faces[vertex.wrapped] = vertex_to_faces.get(vertex.wrapped, []) + [face.wrapped]
     if edges:
         for edge in shape.edges():
-            _tessellate_edge(mgr, edge.wrapped, angular_tolerance, angular_tolerance)
+            _tessellate_edge(mgr, edge.wrapped, edge_to_faces[edge], angular_tolerance, angular_tolerance)
     if vertices:
         for vertex in shape.vertices():
-            _tessellate_vertex(mgr, vertex.wrapped)
+            _tessellate_vertex(mgr, vertex_to_faces[vertex], vertex.wrapped)
 
     return mgr.gltf
 
@@ -70,19 +79,37 @@ def _tessellate_face(
     mgr.add_face(vertices, indices, uv)
 
 
+def _push_point(v: Tuple[float, float, float], faces: List[TopoDS_Face]) -> Tuple[float, float, float]:
+    # Use the connected faces to push edges/vertices and make them always visible
+    push_dir = (0, 0, 0)
+    for ocp_face in faces:
+        normal = Face(ocp_face).normal_at(v)
+        push_dir = (push_dir[0] + normal.X, push_dir[1] + normal.Y, push_dir[2] + normal.Z)
+    if push_dir != (0, 0, 0):
+        # Normalize the push direction by the number of faces and a constant factor
+        # NOTE: Don't overdo it, or metrics will be wrong
+        n = len(faces) / 1e-3
+        push_dir = (push_dir[0] / n, push_dir[1] / n, push_dir[2] / n)
+        # Push the vertex by the normal
+        v = (v[0] + push_dir[0], v[1] + push_dir[1], v[2] + push_dir[2])
+    return v
+
+
 def _tessellate_edge(
         mgr: GLTFMgr,
         ocp_edge: TopoDS_Edge,
+        faces: List[TopoDS_Face],
         angular_deflection: float = 0.1,
         curvature_deflection: float = 0.1,
 ):
+    # Use a curve discretizer to get the vertices
     curve = BRepAdaptor_Curve(ocp_edge)
     discretizer = GCPnts_TangentialDeflection(curve, angular_deflection, curvature_deflection)
     assert discretizer.NbPoints() > 1, "Edge is too small??"
 
     # add vertices
     vertices = [
-        (v.X(), v.Y(), v.Z())
+        _push_point((v.X(), v.Y(), v.Z()), faces)
         for v in (
             discretizer.Value(i)  # .Transformed(transformation)
             for i in range(1, discretizer.NbPoints() + 1)
@@ -91,9 +118,9 @@ def _tessellate_edge(
     mgr.add_edge(vertices)
 
 
-def _tessellate_vertex(mgr: GLTFMgr, ocp_vertex: TopoDS_Vertex):
+def _tessellate_vertex(mgr: GLTFMgr, ocp_vertex: TopoDS_Vertex, faces: List[TopoDS_Face]):
     c = Vertex(ocp_vertex).center()
-    mgr.add_vertex((c.X, c.Y, c.Z))
+    mgr.add_vertex(_push_point((c.X, c.Y, c.Z), faces))
 
 
 def _hashcode(obj: TopoDS_Shape) -> str: