From 409dd3fe9d2fec0185e123edef568cfb3f9f947d Mon Sep 17 00:00:00 2001
From: ochafik <ochafik@google.com>
Date: Thu, 16 Mar 2023 03:41:09 +0000
Subject: [PATCH] [flatten] Refine rules about tree flattening + added test
 case

---
 src/manifold/src/csg_tree.cpp | 39 +++++++++++++++++++++++------------
 test/manifold_test.cpp        | 28 +++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 13 deletions(-)

diff --git a/src/manifold/src/csg_tree.cpp b/src/manifold/src/csg_tree.cpp
index cf94ddb60..07796ce83 100644
--- a/src/manifold/src/csg_tree.cpp
+++ b/src/manifold/src/csg_tree.cpp
@@ -254,21 +254,34 @@ std::shared_ptr<CsgNode> CsgOpNode::Boolean(
     const std::shared_ptr<CsgNode> &second, OpType op) {
   std::vector<std::shared_ptr<CsgNode>> children;
 
-  auto handleOperand = [&](const std::shared_ptr<CsgNode> &operand) {
-    if (auto opNode = std::dynamic_pointer_cast<CsgOpNode>(operand)) {
-      if ((opNode->IsOp(op) ||
-           (op == OpType::Subtract && opNode->IsOp(OpType::Add))) &&
-          opNode->impl_.UseCount() == 1) {
-        for (auto &child : opNode->GetChildren(/* forceToLeafNodes= */ false)) {
-          children.push_back(child);
-        }
-        return;
-      }
+  if (IsOp(op) && (impl_.UseCount() == 1)) {
+    auto impl = impl_.GetGuard();
+    std::copy(impl->children_.begin(), impl->children_.end(),
+              std::back_inserter(children));
+  } else {
+    children.push_back(shared_from_this());
+  }
+
+  auto secondOp = std::dynamic_pointer_cast<CsgOpNode>(second);
+  auto canInlineSecondOp = [&]() {
+    switch (op) {
+      case OpType::Add:
+      case OpType::Intersect:
+        return secondOp->IsOp(op);
+      case OpType::Subtract:
+        return secondOp->IsOp(OpType::Add);
+      default:
+        return false;
     }
-    children.push_back(operand);
   };
-  handleOperand(shared_from_this());
-  handleOperand(second);
+
+  if (secondOp && (secondOp->impl_.UseCount() == 1) && canInlineSecondOp()) {
+    auto secondImpl = secondOp->impl_.GetGuard();
+    std::copy(secondImpl->children_.begin(), secondImpl->children_.end(),
+              std::back_inserter(children));
+  } else {
+    children.push_back(second);
+  }
 
   return std::make_shared<CsgOpNode>(children, op);
 }
diff --git a/test/manifold_test.cpp b/test/manifold_test.cpp
index 52a8135bb..f00f3a8e5 100644
--- a/test/manifold_test.cpp
+++ b/test/manifold_test.cpp
@@ -505,3 +505,31 @@ TEST(Manifold, MirrorUnion) {
   EXPECT_FLOAT_EQ(vol_a * 2.75, result.GetProperties().volume);
   EXPECT_TRUE(a.Mirror(glm::vec3(0)).IsEmpty());
 }
+
+TEST(Manifold, BooleanVolumes) {
+  glm::mat4 m = glm::translate(glm::mat4(1.0f), glm::vec3(1.0f));
+
+  // Define solids which volumes are easy to compute w/ bit arithmetics:
+  // m1, m2, m4 are unique, non intersecting "bits" (of volume 1, 2, 4)
+  // m3 = m1 + m2
+  // m7 = m1 + m2 + m3
+  auto m1 = Manifold::Cube({1, 1, 1});
+  auto m2 = Manifold::Cube({2, 1, 1}).Transform(
+      glm::translate(glm::mat4(1.0f), glm::vec3(1.0f, 0, 0)));
+  auto m4 = Manifold::Cube({4, 1, 1}).Transform(
+      glm::translate(glm::mat4(1.0f), glm::vec3(3.0f, 0, 0)));
+  auto m3 = Manifold::Cube({3, 1, 1});
+  auto m7 = Manifold::Cube({7, 1, 1});
+
+  EXPECT_FLOAT_EQ((m1 ^ m2).GetProperties().volume, 0);
+  EXPECT_FLOAT_EQ((m1 + m2 + m4).GetProperties().volume, 7);
+  EXPECT_FLOAT_EQ((m1 + m2 - m4).GetProperties().volume, 3);
+  EXPECT_FLOAT_EQ((m1 + (m2 ^ m4)).GetProperties().volume, 1);
+  EXPECT_FLOAT_EQ((m7 ^ m4).GetProperties().volume, 4);
+  EXPECT_FLOAT_EQ((m7 ^ m3 ^ m1).GetProperties().volume, 1);
+  EXPECT_FLOAT_EQ((m7 ^ (m1 + m2)).GetProperties().volume, 3);
+  EXPECT_FLOAT_EQ((m7 - m4).GetProperties().volume, 3);
+  EXPECT_FLOAT_EQ((m7 - m4 - m2).GetProperties().volume, 1);
+  EXPECT_FLOAT_EQ((m7 - (m7 - m1)).GetProperties().volume, 1);
+  EXPECT_FLOAT_EQ((m7 - (m1 + m2)).GetProperties().volume, 4);
+}