From 1d44827f96b3862e2c25bc11bf9b6b80218321e1 Mon Sep 17 00:00:00 2001
From: Stephen Seo <seo.disparate@gmail.com>
Date: Mon, 6 May 2024 14:28:23 +0900
Subject: [PATCH] Add combine AABB function

New function that creates a new AABB that encompasses the two given
AABBs.
---
 src/sc_sacd.cpp | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/sc_sacd.h   |  4 ++++
 src/test.cpp    | 15 ++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/src/sc_sacd.cpp b/src/sc_sacd.cpp
index 070f4e8..62a7d40 100644
--- a/src/sc_sacd.cpp
+++ b/src/sc_sacd.cpp
@@ -627,3 +627,55 @@ SC_SACD_AABB_Box SC_SACD_Generic_Box_To_AABB(const SC_SACD_Generic_Box s) {
 
   return aabb;
 }
+
+SC_SACD_AABB_Box SC_SACD_AABB_Combine(const SC_SACD_AABB_Box a,
+                                      const SC_SACD_AABB_Box b) {
+  SC_SACD_Vec3 min, max;
+
+  // Populate min values.
+
+  float temp_a = a.x - a.width / 2.0F;
+  float temp_b = b.x - b.width / 2.0F;
+
+  min.x = temp_a < temp_b ? temp_a : temp_b;
+
+  temp_a = a.y - a.height / 2.0F;
+  temp_b = b.y - b.height / 2.0F;
+
+  min.y = temp_a < temp_b ? temp_a : temp_b;
+
+  temp_a = a.z - a.depth / 2.0F;
+  temp_b = b.z - b.depth / 2.0F;
+
+  min.z = temp_a < temp_b ? temp_a : temp_b;
+
+  // Populate max values.
+
+  temp_a = a.x + a.width / 2.0F;
+  temp_b = b.x + b.width / 2.0F;
+
+  max.x = temp_a > temp_b ? temp_a : temp_b;
+
+  temp_a = a.y + a.height / 2.0F;
+  temp_b = b.y + b.height / 2.0F;
+
+  max.y = temp_a > temp_b ? temp_a : temp_b;
+
+  temp_a = a.z + a.depth / 2.0F;
+  temp_b = b.z + b.depth / 2.0F;
+
+  max.z = temp_a > temp_b ? temp_a : temp_b;
+
+  // Populate the result.
+
+  temp_a = max.x - min.x;
+  temp_b = max.y - min.y;
+  float temp_c = max.z - min.z;
+
+  return SC_SACD_AABB_Box{min.x + temp_a / 2.0F,
+                          min.y + temp_b / 2.0F,
+                          min.z + temp_c / 2.0F,
+                          temp_a,
+                          temp_b,
+                          temp_c};
+}
diff --git a/src/sc_sacd.h b/src/sc_sacd.h
index b18dcef..bf5725d 100644
--- a/src/sc_sacd.h
+++ b/src/sc_sacd.h
@@ -137,6 +137,10 @@ SC_SACD_EXPORT SC_SACD_AABB_Box SC_SACD_Sphere_To_AABB(const SC_SACD_Sphere s);
 SC_SACD_EXPORT SC_SACD_AABB_Box
 SC_SACD_Generic_Box_To_AABB(const SC_SACD_Generic_Box s);
 
+/// Combines AABB's such that the new AABB encompasses the two AABB's.
+SC_SACD_EXPORT SC_SACD_AABB_Box SC_SACD_AABB_Combine(const SC_SACD_AABB_Box a,
+                                                     const SC_SACD_AABB_Box b);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/test.cpp b/src/test.cpp
index 83b08ea..4986e1a 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -681,6 +681,21 @@ int main() {
     CHECK_FLOAT(aabb.depth, box.depth);
   }
 
+  // Test combining AABB.
+  {
+    SC_SACD_AABB_Box a{5.0F, 5.0F, 5.0F, 2.0F, 2.0F, 2.0F};
+
+    SC_SACD_AABB_Box b{-3.0F, -3.0F, -3.0F, 2.0F, 2.0F, 2.0F};
+
+    auto combined = SC_SACD_AABB_Combine(a, b);
+    CHECK_FLOAT(combined.x, (7.0F - 5.0F) / 2.0F);
+    CHECK_FLOAT(combined.y, (7.0F - 5.0F) / 2.0F);
+    CHECK_FLOAT(combined.z, (7.0F - 5.0F) / 2.0F);
+    CHECK_FLOAT(combined.width, 10.0F);
+    CHECK_FLOAT(combined.height, 10.0F);
+    CHECK_FLOAT(combined.depth, 10.0F);
+  }
+
   std::cout << "Checks checked: " << checks_checked << '\n'
             << "Checks passed:  " << checks_passed << '\n';