From f40037a4a04933d66b6025873d2483169848fb74 Mon Sep 17 00:00:00 2001
From: Matthew Kosarek <mattkae@protonmail.com>
Date: Wed, 12 May 2021 20:28:30 -0400
Subject: Decently good interaction between rectangles. I am happy for now

---
 .../rectangle_rectangle/dist/output.wasm           | Bin 55475 -> 55719 bytes
 .../2d/_collisions/rectangle_rectangle/main.cpp    |  62 ++++++++++++---------
 2 files changed, 36 insertions(+), 26 deletions(-)

diff --git a/frontend/2d/_collisions/rectangle_rectangle/dist/output.wasm b/frontend/2d/_collisions/rectangle_rectangle/dist/output.wasm
index 66f6ab8..a6d85e9 100755
Binary files a/frontend/2d/_collisions/rectangle_rectangle/dist/output.wasm and b/frontend/2d/_collisions/rectangle_rectangle/dist/output.wasm differ
diff --git a/frontend/2d/_collisions/rectangle_rectangle/main.cpp b/frontend/2d/_collisions/rectangle_rectangle/main.cpp
index 9f6db62..37cce89 100644
--- a/frontend/2d/_collisions/rectangle_rectangle/main.cpp
+++ b/frontend/2d/_collisions/rectangle_rectangle/main.cpp
@@ -60,6 +60,12 @@ struct IntersectionResult {
     Vector2 secondPointOfApplication;
 };
 
+struct Edge {
+	Vector2 normal;
+	Vector2 start;
+	Vector2 end;
+};
+
 struct Rectangle {
 	OrthographicShape shape;
 	Rigidbody body;
@@ -138,25 +144,19 @@ struct Rectangle {
 		pointList[3] = botRight;
 	}
 
-    void getEdges(Vector2* edgeList) {
+    void getEdges(Edge* edgeList) {
 		Vector2 pointsList[4];
 		getPoints(pointsList);
 
 		for (int i = 0; i < 4; i++) {
+			edgeList[i].start =  pointsList[i];
 			if (i + 1 == 4) {
-				edgeList[i] =  pointsList[i] - pointsList[0];
+				edgeList[i].end = pointsList[0];
 			} else {
-				edgeList[i] =  pointsList[i] - pointsList[i + 1];
+				edgeList[i].end = pointsList[i + 1];
 			}
-		}
-	}
-
-	void getNormals(Vector2* normalList) {
-		Vector2 edgeList[4];
-		getEdges(edgeList);
 
-		for (int i = 0; i < 4; i++) {
-			normalList[i] = edgeList[i].getPerp().normalize();
+			edgeList[i].normal = (edgeList[i].end - edgeList[i].start).getPerp().normalize();
 		}
 	}
 };
@@ -236,23 +236,23 @@ IntersectionResult getIntersection(Rectangle* first, Rectangle* second) {
 	IntersectionResult ir;
 
 	// For two rectangles to overlap, it means that at least one of the corners of one is inside of the other
-	Vector2 firstNormals[4];
-	first->getNormals(firstNormals);
+    Edge firstEdges[4];
+	first->getEdges(firstEdges);
 	Vector2 firstPoints[4];
 	first->getPoints(firstPoints);
 
-	Vector2 secondNormals[4];
-	second->getNormals(secondNormals);
+    Edge secondEdges[4];
+	second->getEdges(secondEdges);
 	Vector2 secondPoints[4];
     second->getPoints(secondPoints);
 
 	float32 minOverlap = FLT_MAX;
 	Vector2 minOverlapAxis;
-    bool minOverlapAxisIsFromFirstRectangle = true;
+	Edge* minOverlapEdge = NULL;
+	bool minOverlapWasFirstRect = false;
     
-
 	for (int i = 0; i < 4; i++) {
-		Vector2 normal = firstNormals[i];
+		Vector2 normal = firstEdges[i].normal;
 
 	    Vector2 firstProj = getProjection(firstPoints, normal);
 		Vector2 secondProj = getProjection(secondPoints, normal);
@@ -265,12 +265,13 @@ IntersectionResult getIntersection(Rectangle* first, Rectangle* second) {
 		if (overlap < minOverlap) {
 			minOverlap = overlap;
 			minOverlapAxis = normal;
-            minOverlapAxisIsFromFirstRectangle = true;
+			minOverlapEdge = &firstEdges[i];
+			minOverlapWasFirstRect = true;
 		}
 	}
 
 	for (int i = 0; i < 4; i++) {
-		Vector2 normal = secondNormals[i];
+		Vector2 normal = secondEdges[i].normal;
 
 	    Vector2 firstProj = getProjection(firstPoints, normal);
 		Vector2 secondProj = getProjection(secondPoints, normal);
@@ -283,7 +284,7 @@ IntersectionResult getIntersection(Rectangle* first, Rectangle* second) {
 		if (overlap < minOverlap) {
 			minOverlap = overlap;
 			minOverlapAxis = normal;
-            minOverlapAxisIsFromFirstRectangle = false;
+			minOverlapEdge = &secondEdges[i];
 		}
 	}
 
@@ -303,16 +304,25 @@ IntersectionResult getIntersection(Rectangle* first, Rectangle* second) {
     // Rectangle is the collision point. This enables us to then solve for their respective points of application fairly
     // easily. If the collision "point" is an entire face, we make the collision point be the center point.
     //
-    Vector2 topPlane;
-    Vector2 bottomPlane;
+
+	Vector2 closestPoint;
+	float32 minDistance = FLT_MAX;
 
     for (int p = 0; p < 4; p++) {
-        Vector2 point = minOverlapAxisIsFromFirstRectangle ? first->getPoint(p) : second->getPoint(p);
+		Vector2 point = minOverlapWasFirstRect ? secondPoints[p] : firstPoints[p];
 
+		float32 distFromPointToStart = (minOverlapEdge->start - point).length();
+		float32 distFromPointToEnd = (minOverlapEdge->end - point).length();
+		float32 potentialMin = MIN(distFromPointToStart, distFromPointToEnd);
+
+		if (potentialMin < minDistance) {
+			closestPoint = point;
+			minDistance = potentialMin; 
+		}
     }
 
-    ir.firstPointOfApplication = Vector2();
-    ir.secondPointOfApplication = Vector2();
+    ir.firstPointOfApplication = closestPoint - first->body.position;
+    ir.secondPointOfApplication = closestPoint - second->body.position;;
 
 	return ir;
 }
-- 
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