Honestly, a much better simulation going on here

14 files changed, 60 insertions, 58 deletions

diff --git a/2d/_collisions/polygon_polygon/dist/output.wasm b/2d/_collisions/polygon_polygon/dist/output.wasm
index 8e0443b..5b2ba39 100755
--- a/2d/_collisions/polygon_polygon/dist/output.wasm
+++ b/2d/_collisions/polygon_polygon/dist/output.wasm
diff --git a/2d/_collisions/polygon_polygon/images/1.png b/2d/_collisions/polygon_polygon/images/1.png
index 0e4268a..d554c2a 100644
--- a/2d/_collisions/polygon_polygon/images/1.png
+++ b/2d/_collisions/polygon_polygon/images/1.png
diff --git a/2d/_collisions/polygon_polygon/images/2.png b/2d/_collisions/polygon_polygon/images/2.png
index 3dd2020..67f379c 100644
--- a/2d/_collisions/polygon_polygon/images/2.png
+++ b/2d/_collisions/polygon_polygon/images/2.png
diff --git a/2d/_collisions/polygon_polygon/images/2a.png b/2d/_collisions/polygon_polygon/images/2a.png
index 02bfa02..6e2d4b2 100644
--- a/2d/_collisions/polygon_polygon/images/2a.png
+++ b/2d/_collisions/polygon_polygon/images/2a.png
diff --git a/2d/_collisions/polygon_polygon/images/2b.png b/2d/_collisions/polygon_polygon/images/2b.png
index 1cfc780..f1fbcc4 100644
--- a/2d/_collisions/polygon_polygon/images/2b.png
+++ b/2d/_collisions/polygon_polygon/images/2b.png
diff --git a/2d/_collisions/polygon_polygon/images/2c.png b/2d/_collisions/polygon_polygon/images/2c.png
index d9ca28b..bdecfb2 100644
--- a/2d/_collisions/polygon_polygon/images/2c.png
+++ b/2d/_collisions/polygon_polygon/images/2c.png
diff --git a/2d/_collisions/polygon_polygon/images/2d.png b/2d/_collisions/polygon_polygon/images/2d.png
index 8e6f6cc..932a7c3 100644
--- a/2d/_collisions/polygon_polygon/images/2d.png
+++ b/2d/_collisions/polygon_polygon/images/2d.png
diff --git a/2d/_collisions/polygon_polygon/images/2e.png b/2d/_collisions/polygon_polygon/images/2e.png
index fdaeae3..3a47d46 100644
--- a/2d/_collisions/polygon_polygon/images/2e.png
+++ b/2d/_collisions/polygon_polygon/images/2e.png
diff --git a/2d/_collisions/polygon_polygon/images/2f.png b/2d/_collisions/polygon_polygon/images/2f.png
index 9a862b5..774830f 100644
--- a/2d/_collisions/polygon_polygon/images/2f.png
+++ b/2d/_collisions/polygon_polygon/images/2f.png
diff --git a/2d/_collisions/polygon_polygon/images/3.png b/2d/_collisions/polygon_polygon/images/3.png
index 0e6d218..22eddde 100644
--- a/2d/_collisions/polygon_polygon/images/3.png
+++ b/2d/_collisions/polygon_polygon/images/3.png
diff --git a/2d/_collisions/polygon_polygon/images/3a.png b/2d/_collisions/polygon_polygon/images/3a.png
new file mode 100644
index 0000000..cb8626b
--- /dev/null
+++ b/2d/_collisions/polygon_polygon/images/3a.png
diff --git a/2d/_collisions/polygon_polygon/images/3b.png b/2d/_collisions/polygon_polygon/images/3b.png
new file mode 100644
index 0000000..f03fda1
--- /dev/null
+++ b/2d/_collisions/polygon_polygon/images/3b.png
diff --git a/2d/_collisions/polygon_polygon/images/3c.png b/2d/_collisions/polygon_polygon/images/3c.png
new file mode 100644
index 0000000..4f50821
--- /dev/null
+++ b/2d/_collisions/polygon_polygon/images/3c.png
diff --git a/2d/_collisions/polygon_polygon/main.cpp b/2d/_collisions/polygon_polygon/main.cpp
index 348e8d2..8648e94 100644
--- a/2d/_collisions/polygon_polygon/main.cpp
+++ b/2d/_collisions/polygon_polygon/main.cpp
@@ -261,7 +261,20 @@ void load() {
     mainLoop.run(update);
 }
 
-Vector2 getProjection(Vector2* vertices, int numVertices, Vector2 axis) {
+struct SATResult {
+    Edge* minOverlapEdge = NULL;        // Edge that caused the intersection
+    Vector2 overlapPoint;               // Point that caused the intersection on the other shape (i.e. not minOverlapShape)
+    float32 minOverlap = FLT_MAX;       // Smallest projection overlap
+};
+
+struct ProjectionResult {
+    Vector2 minVertex;
+    Vector2 maxVertex;
+    Vector2 projection;
+};
+
+ProjectionResult getProjection(Vector2* vertices, int numVertices, Vector2 axis) {
+    ProjectionResult pr;
 	float32 min = axis.dot(vertices[0]);
 	float32 max = min;
 
@@ -269,13 +282,16 @@ Vector2 getProjection(Vector2* vertices, int numVertices, Vector2 axis) {
 		float32 d = axis.dot(vertices[v]);
 
 		if (d < min) {
+            pr.minVertex = vertices[v];
 			min = d;
 		} else if (d > max) {
+            pr.maxVertex = vertices[v];
 			max = d;
 		}
 	}
-
-	return Vector2 { min, max };
+    
+    pr.projection = Vector2 { min, max };
+	return pr;
 }
 
 bool projectionsOverlap(Vector2 first, Vector2 second) {
@@ -288,74 +304,60 @@ float32 getProjectionOverlap(Vector2 first, Vector2 second) {
 	return e - f;
 }
 
-const float32 EPSILON = 1.f;
-IntersectionResult getIntersection(ConvexPolygon* first, ConvexPolygon* second) {
-	IntersectionResult ir;
-
-	// For two rectangles to overlap, it means that at least one of the corners of one is inside of the other
-	float32 minOverlap = FLT_MAX;
-	Edge* minOverlapEdge = NULL;
-	bool minOverlapWasFirst = false;
-    
-	for (int i = 0; i < first->numVertices; i++) {
+bool runSatForShapesEdges(SATResult* result, ConvexPolygon* first, ConvexPolygon* second) {
+    for (int i = 0; i < first->numVertices; i++) {
 		Vector2 normal = first->edges[i].normal;
 
-	    Vector2 firstProj = getProjection(first->transformedVertices, first->numVertices, normal);
-		Vector2 secondProj = getProjection(second->transformedVertices, second->numVertices, normal);
+	    ProjectionResult firstProj = getProjection(first->transformedVertices, first->numVertices, normal);
+	    ProjectionResult secondProj = getProjection(second->transformedVertices, second->numVertices, normal);
 
-		if (!projectionsOverlap(firstProj, secondProj)) {
-			return ir;
+		if (!projectionsOverlap(firstProj.projection, secondProj.projection)) {
+			return false;
 		}
 
-		float32 overlap = getProjectionOverlap(firstProj, secondProj);
-		if (overlap < minOverlap) {
-			minOverlap = overlap;
-			minOverlapEdge = &first->edges[i];
-			minOverlapWasFirst = true;
+		float32 overlap = getProjectionOverlap(firstProj.projection, secondProj.projection);
+		if (overlap < result->minOverlap) {
+			result->minOverlap = overlap;
+			result->minOverlapEdge = &first->edges[i];
+            
+            // The overlapPoint will be the point on the other shape that penetrated the edge.
+            // If we caught the intersection reasonably early, it should be the point on 'second'
+            // that is nearest to the points on 'first'.
+            float32 min1min2 = (firstProj.minVertex - secondProj.minVertex).length();
+            float32 min1max2 = (firstProj.minVertex - secondProj.maxVertex).length();
+            float32 max1max2 = (firstProj.maxVertex - secondProj.maxVertex).length();
+            float32 max1min2 = (firstProj.maxVertex - secondProj.minVertex).length();
+            
+            float32 closest = MIN(min1min2, MIN(min1max2, MIN(max1max2, max1min2)));
+            if (closest == min1min2 || closest == max1min2) {
+                result->overlapPoint = secondProj.minVertex;
+            } else {
+                result->overlapPoint = secondProj.maxVertex;
+            }
 		}
 	}
 
-	for (int i = 0; i < second->numVertices; i++) {
-		Vector2 normal = second->edges[i].normal;
-
-	    Vector2 firstProj = getProjection(first->transformedVertices, first->numVertices, normal);
-		Vector2 secondProj = getProjection(second->transformedVertices, second->numVertices, normal);
+    return true;
+}
 
-		if (!projectionsOverlap(firstProj, secondProj)) {
-			return ir;
-		}
+const float32 EPSILON = 1.f;
+IntersectionResult getIntersection(ConvexPolygon* first, ConvexPolygon* second) {
+	IntersectionResult ir;
+    SATResult sat;
+    
+    if (!runSatForShapesEdges(&sat, first, second)) {
+        return ir;
+    }
 
-		float32 overlap = getProjectionOverlap(firstProj, secondProj);
-		if (overlap < minOverlap) {
-			minOverlap = overlap;
-			minOverlapEdge = &second->edges[i];
-            minOverlapWasFirst = false;
-		}
-	}
+    if (!runSatForShapesEdges(&sat, second, first)) {
+        return ir;
+    }
 
 	ir.intersect = true;
 	ir.relativeVelocity = first->body.velocity - second->body.velocity;
-	ir.collisionNormal = minOverlapEdge->normal;
-
-    // Time to find just where we intersected
-	Vector2 closestPoint;
-	float32 minDistance = FLT_MAX;
-    
-    for (int p = 0; p < (minOverlapWasFirst ? second->numVertices : first->numVertices); p++) {
-		Vector2 point = minOverlapWasFirst ? second->transformedVertices[p] : first->transformedVertices[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 = closestPoint - first->body.position;
-    ir.secondPointOfApplication = closestPoint - second->body.position;;
+	ir.collisionNormal = sat.minOverlapEdge->normal;
+    ir.firstPointOfApplication = sat.overlapPoint - first->body.position;
+    ir.secondPointOfApplication = sat.overlapPoint - second->body.position;;
 
 	return ir;
 }