From d61f533e2a25d35d7f555f8405bd952708944951 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Mon, 26 May 2025 17:53:27 -0500
Subject: [PATCH] wip

---
 blender_shadow_volume2.py | 90 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 blender_shadow_volume2.py

diff --git a/blender_shadow_volume2.py b/blender_shadow_volume2.py
new file mode 100644
index 0000000..2492080
--- /dev/null
+++ b/blender_shadow_volume2.py
@@ -0,0 +1,90 @@
+import bpy
+import bmesh
+from mathutils import Vector
+from collections import defaultdict
+from dataclasses import dataclass
+
+def sprint(*text):
+    screen = bpy.data.screens['Scripting']
+    for area in screen.areas:
+        if area.type != "CONSOLE":
+            continue
+        override = {'screen': screen, 'area': area}
+        with bpy.context.temp_override(**override):
+            bpy.ops.console.scrollback_append(text=" ".join(map(str, text)))
+
+print = sprint
+
+def face_indicators(light: Vector,
+                    position: list[Vector],
+                    polygon_normal: list[Vector],
+                    mesh: bpy.types.Mesh,
+                    # outputs
+                    indicators: list[float]):
+    for i in range(len(mesh.polygons)):
+        n = polygon_normal[i]
+        p = position[mesh.polygons[i].a]
+        indicator = dot(n, (light - p))
+        indicators[i] = indicator
+
+@dataclass
+class Edge:
+    a: int # vertex index
+    b: int # vertex index
+
+@dataclass
+class PolygonIndex:
+    a: int
+    b: int
+
+@dataclass
+class EdgePolygon:
+    edge: Edge
+    polygon_index: PolygonIndex
+
+def build_edge_polygons(mesh: bpy.types.Mesh):
+    by_edge = defaultdict(list)
+    for i, polygon in enumerate(mesh.polygons):
+        for edge in polygon.edge_keys:
+            by_edge[frozenset(edge)].append(i)
+
+    assert all(len(p) == 2 for p in by_edge.values())
+
+    return [
+        EdgePolygon(Edge(*edge), PolygonIndex(*polygons))
+        for edge, polygons in by_edge.items()
+    ]
+
+def object_silhouette(indicators: list[float],
+                      mesh: bpy.types.Mesh,
+                      # outputs
+                      edge_indices: list[int]):
+    ix = 0
+
+    edge_polygons = build_edge_polygons(mesh)
+
+    for i in range(len(edge_polygons)):
+        ep = edge_polygons[i]
+        if (indicators[ep.polygon_index.a] > 0) != (indicators[ep.polygon_index.b]):
+            edge_indices[ix] = i
+            ix += 1
+
+    return ix
+
+def select_edge(bm, edge):
+    for e in bm.edges:
+        if frozenset((e.verts[0].index, e.verts[1].index)) == frozenset(edge):
+            e.select = True
+
+def select():
+    light = bpy.data.objects['Light']
+    torus = bpy.data.objects['Torus']
+
+    position = [0] * len(
+
+    obj = bpy.context.edit_object
+    bm = bmesh.from_edit_mesh(obj.data)
+
+
+
+    bmesh.update_edit_mesh(obj.data)