新增基于摄像机网格投影的黑白笔画原型

沿用彩色块的网格与可见性投影，便于评估透视适配的笔画。已通过几何单元测试及 250/500 像素光流探针。

blender/scripts/camera_grid_stroke_geometry.py

@@ -0,0 +1,46 @@
+"""Convex camera-cell stroke shapes and perspective-preserving clipping."""
+
+import math
+import random
+
+from patch_geometry import clip_halfspace, interpolate_uv
+
+
+def capsule_in_cell(i, j, nx, ny, seed, width_ratio=0.42, length_ratio=0.84):
+    """Return a round-ended stroke wholly inside one normalized camera cell."""
+    if not 0 < width_ratio <= length_ratio < 1:
+        raise ValueError("require 0 < width_ratio <= length_ratio < 1")
+    rng = random.Random((seed * 1000003 + i * 9176 + j * 6113) & 0xFFFFFFFF)
+    angle = rng.uniform(0, math.pi)
+    radius = width_ratio / 2
+    half_body = (length_ratio - width_ratio) / 2
+    outline = []
+    for centre, start in ((half_body, -math.pi / 2), (-half_body, math.pi / 2)):
+        for step in range(9):
+            theta = start + math.pi * step / 8
+            x = centre + radius * math.cos(theta)
+            y = radius * math.sin(theta)
+            xr = x * math.cos(angle) - y * math.sin(angle)
+            yr = x * math.sin(angle) + y * math.cos(angle)
+            outline.append(((i + 0.5 + xr) / nx, (j + 0.5 + yr) / ny))
+    return outline
+
+
+def clip_to_stroke(fragment, outline):
+    """Clip a projected triangle while retaining its perspective attributes."""
+    points = fragment
+    for a, b in zip(outline, outline[1:] + outline[:1]):
+        dx, dy = b[0] - a[0], b[1] - a[1]
+        points = clip_halfspace(
+            points,
+            lambda p, a=a, dx=dx, dy=dy: dx * (p[1] - a[1]) - dy * (p[0] - a[0]),
+        )
+        if len(points) < 3:
+            return []
+    return points
+
+
+def projected_stroke_uv(fragment, loop_uvs, outline):
+    """Resolve a clipped camera stroke through the same UV interpolation as patches."""
+    return [interpolate_uv(point, loop_uvs)
+            for point in clip_to_stroke(fragment, outline)]