From d100932a9ef6f07cd909a70350a06add10557711 Mon Sep 17 00:00:00 2001
From: maelstrom <maelstrom@maelstrom.dev>
Date: Wed, 30 Apr 2025 16:45:46 +0200
Subject: [PATCH] fix(part): non-touching parts whos surfaces are on the same
 plane were joining

---
 core/src/datatypes/vector.cpp |  8 ++++++++
 core/src/datatypes/vector.h   |  3 +++
 core/src/objects/part.cpp     | 27 +++++++++++++++++++++++++++
 core/src/objects/part.h       |  1 +
 4 files changed, 39 insertions(+)

diff --git a/core/src/datatypes/vector.cpp b/core/src/datatypes/vector.cpp
index 44e4193..119d1fe 100644
--- a/core/src/datatypes/vector.cpp
+++ b/core/src/datatypes/vector.cpp
@@ -62,6 +62,14 @@ bool Data::Vector3::operator ==(Data::Vector3 other) const {
     return this->X() == other.X() && this->Y() == other.Y() && this->Z() == other.Z();
 }
 
+bool Data::Vector3::operator <(Data::Vector3 other) const {
+    return X() < other.X() && Y() < other.Y() && Z() < other.Z();
+}
+
+bool Data::Vector3::operator >(Data::Vector3 other) const {
+    return X() > other.X() && Y() > other.Y() && Z() > other.Z();
+}
+
 Data::Vector3 Data::Vector3::Cross(Data::Vector3 other) const {
     return glm::cross(this->vector, other.vector);
 }
diff --git a/core/src/datatypes/vector.h b/core/src/datatypes/vector.h
index 100966f..3442bc1 100644
--- a/core/src/datatypes/vector.h
+++ b/core/src/datatypes/vector.h
@@ -52,6 +52,9 @@ namespace Data {
         Data::Vector3 operator -(Data::Vector3) const;
         Data::Vector3 operator -() const;
 
+        bool operator <(Data::Vector3) const;
+        bool operator >(Data::Vector3) const;
+
         bool operator ==(Data::Vector3) const;
     };
 }
diff --git a/core/src/objects/part.cpp b/core/src/objects/part.cpp
index 61e4e7a..3c952a4 100644
--- a/core/src/objects/part.cpp
+++ b/core/src/objects/part.cpp
@@ -13,6 +13,8 @@
 #include "objects/joint/snap.h"
 #include "rendering/renderer.h"
 #include "rendering/surface.h"
+#include <cstdio>
+#include <glm/common.hpp>
 #include <memory>
 #include <optional>
 
@@ -181,6 +183,30 @@ bool Part::checkJointContinuityUp(std::shared_ptr<Part> otherPart) {
     return true;
 }
 
+bool Part::checkSurfacesTouching(CFrame surfaceFrame, Vector3 myFace, Vector3 otherFace, std::shared_ptr<Part> otherPart) {
+    // Vector3 otherPartCenterToMine = surfaceFrame.Inverse() * otherPart->cframe.Position();
+    Vector3 farCorner0 = surfaceFrame.Inverse() * otherPart->cframe * (Vector3::ONE * (otherPart->size / 2.f));
+    Vector3 farCorner1 = surfaceFrame.Inverse() * otherPart->cframe * (-Vector3::ONE * (otherPart->size / 2.f));
+    
+    Vector3 myFarCorner0 = Vector3::ONE * (size / 2.f);
+    Vector3 myFarCorner1 = -Vector3::ONE * (size / 2.f);
+
+    // https://stackoverflow.com/a/306332/16255372
+    float myTop = glm::max(myFarCorner0.X(), myFarCorner1.X());
+    float myBot = glm::min(myFarCorner0.X(), myFarCorner1.X());
+    float myRight = glm::max(myFarCorner0.Y(), myFarCorner1.Y());
+    float myLeft = glm::min(myFarCorner0.Y(), myFarCorner1.Y());
+    float otherTop = glm::max(farCorner0.X(), farCorner1.X());
+    float otherBot = glm::min(farCorner0.X(), farCorner1.X());
+    float otherRight = glm::max(farCorner0.Y(), farCorner1.Y());
+    float otherLeft = glm::min(farCorner0.Y(), farCorner1.Y());
+
+    bool horizOverlap = myLeft < otherRight && myRight > otherLeft;
+    bool vertOverlap = myBot < otherTop && myTop > otherBot;
+
+    return horizOverlap && vertOverlap;
+}
+
 std::optional<std::shared_ptr<JointInstance>> makeJointFromSurfaces(SurfaceType a, SurfaceType b) {
     if (a == SurfaceWeld || b == SurfaceWeld || a == SurfaceGlue || b == SurfaceGlue) return Weld::New();
     if ((a == SurfaceStuds && (b == SurfaceInlets || b == SurfaceUniversal))
@@ -225,6 +251,7 @@ void Part::MakeJoints() {
                 if (dot > -0.99) continue; // Surface is pointing opposite to ours
 
                 if (abs(surfacePointLocalToMyFrame.Z()) > 0.05) continue; // Surfaces are within 0.05 studs of one another
+                if (!checkSurfacesTouching(surfaceFrame, myFace, otherFace, otherPart)) continue; // Surface do not overlap
                 if (!checkJointContinuity(otherPart)) continue;
 
                 SurfaceType mySurface = surfaceFromFace(faceFromNormal(myFace));
diff --git a/core/src/objects/part.h b/core/src/objects/part.h
index 5cc1769..7a01762 100644
--- a/core/src/objects/part.h
+++ b/core/src/objects/part.h
@@ -43,6 +43,7 @@ protected:
     bool checkJointContinuity(std::shared_ptr<Part>);
     bool checkJointContinuityUp(std::shared_ptr<Part>);
     bool checkJointContinuityDown(std::shared_ptr<Part>);
+    bool checkSurfacesTouching(CFrame surfaceFrame, Vector3 myFace, Vector3 otherFace, std::shared_ptr<Part> otherPart); 
 
     friend JointInstance;