From cdec64e3f15375d0e3250ca06af618a7fca51a9b Mon Sep 17 00:00:00 2001
From: Michael W <50232075+YishiMichael@users.noreply.github.com>
Date: Wed, 10 Nov 2021 00:23:40 +0800
Subject: [PATCH] Add boolean operations for mobjects

---
 manimlib/mobject/boolean_ops.py | 105 ++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 manimlib/mobject/boolean_ops.py

diff --git a/manimlib/mobject/boolean_ops.py b/manimlib/mobject/boolean_ops.py
new file mode 100644
index 00000000..a6b2749f
--- /dev/null
+++ b/manimlib/mobject/boolean_ops.py
@@ -0,0 +1,105 @@
+import numpy as np
+import pathops
+
+from manimlib.mobject.types.vectorized_mobject import VMobject
+
+
+# Boolean operations between 2D mobjects
+# Borrowed from from https://github.com/ManimCommunity/manim/
+
+def _convert_vmobject_to_skia_path(vmobject):
+    path = pathops.Path()
+    subpaths = vmobject.get_subpaths_from_points(vmobject.get_all_points())
+    for subpath in subpaths:
+        quads = vmobject.get_bezier_tuples_from_points(subpath)
+        start = subpath[0]
+        path.moveTo(*start[:2])
+        for p0, p1, p2 in quads:
+            path.quadTo(*p1[:2], *p2[:2])
+        if vmobject.consider_points_equals(subpath[0], subpath[-1]):
+            path.close()
+    return path
+
+
+def _convert_skia_path_to_vmobject(path, vmobject):
+    PathVerb = pathops.PathVerb
+    current_path_start = np.array([0.0, 0.0, 0.0])
+    for path_verb, points in path:
+        if path_verb == PathVerb.CLOSE:
+            vmobject.add_line_to(current_path_start)
+        else:
+            points = np.hstack((np.array(points), np.zeros((len(points), 1))))
+            if path_verb == PathVerb.MOVE:
+                for point in points:
+                    current_path_start = point
+                    vmobject.start_new_path(point)
+            elif path_verb == PathVerb.CUBIC:
+                vmobject.add_cubic_bezier_curve_to(*points)
+            elif path_verb == PathVerb.LINE:
+                vmobject.add_line_to(points[0])
+            elif path_verb == PathVerb.QUAD:
+                vmobject.add_quadratic_bezier_curve_to(*points)
+            else:
+                raise Exception(f"Unsupported: {path_verb}")
+    return vmobject
+
+
+class Union(VMobject):
+    def __init__(self, *vmobjects, **kwargs):
+        if len(vmobjects) < 2:
+            raise ValueError("At least 2 mobjects needed for Union.")
+        super().__init__(**kwargs)
+        outpen = pathops.Path()
+        paths = [
+            _convert_vmobject_to_skia_path(vmobject)
+            for vmobject in vmobjects
+        ]
+        pathops.union(paths, outpen.getPen())
+        _convert_skia_path_to_vmobject(outpen, self)
+
+
+class Difference(VMobject):
+    def __init__(self, subject, clip, **kwargs):
+        super().__init__(**kwargs)
+        outpen = pathops.Path()
+        pathops.difference(
+            [_convert_vmobject_to_skia_path(subject)],
+            [_convert_vmobject_to_skia_path(clip)],
+            outpen.getPen(),
+        )
+        _convert_skia_path_to_vmobject(outpen, self)
+
+
+class Intersection(VMobject):
+    def __init__(self, *vmobjects, **kwargs):
+        if len(vmobjects) < 2:
+            raise ValueError("At least 2 mobjects needed for Intersection.")
+        super().__init__(**kwargs)
+        outpen = pathops.Path()
+        pathops.intersection(
+            [_convert_vmobject_to_skia_path(vmobjects[0])],
+            [_convert_vmobject_to_skia_path(vmobjects[1])],
+            outpen.getPen(),
+        )
+        new_outpen = outpen
+        for _i in range(2, len(vmobjects)):
+            new_outpen = pathops.Path()
+            pathops.intersection(
+                [outpen],
+                [_convert_vmobject_to_skia_path(vmobjects[_i])],
+                new_outpen.getPen(),
+            )
+            outpen = new_outpen
+        _convert_skia_path_to_vmobject(outpen, self)
+
+
+class Exclusion(VMobject):
+    def __init__(self, subject, clip, **kwargs):
+        super().__init__(**kwargs)
+        outpen = pathops.Path()
+        pathops.xor(
+            [_convert_vmobject_to_skia_path(subject)],
+            [_convert_vmobject_to_skia_path(clip)],
+            outpen.getPen(),
+        )
+        _convert_skia_path_to_vmobject(outpen, self)