Updating roadmap, and getting started on SAT collisions

1 files changed, 40 insertions, 7 deletions

diff --git a/2d/_collisions/polygon_polygon.html b/2d/_collisions/polygon_polygon.html
index 23658ce..ce26f62 100644
--- a/2d/_collisions/polygon_polygon.html
+++ b/2d/_collisions/polygon_polygon.html
@@ -26,7 +26,7 @@
 					<li><label>Collisions</label></li>
 					<li><a title="/2d/_collisions/rectangle_line.html" href="/2d/_collisions/rectangle_line.html">Rectangle-Line</a></li>
 					<li><a title="/2d/_collisions/rectangle_rectangle.html" href="/2d/_collisions/rectangle_rectangle.html">Rectangle-Rectangle</a></li>
-					<li><a title="/2d/_collisions/polygon_polygon.html" href="/2d/_collisions/polygon_polygon.html">Polygon-Polygon</a></li>
+					<li><a title="/2d/_collisions/polygon_polygon.html" href="/2d/_collisions/polygon_polygon.html">Separating Axis Theorem</a></li>
 				</ul>
 			</li>
 			<li>
@@ -67,8 +67,40 @@
   
 </script>
 <article>
-  <h1>Polygon Intersections</h1>
+  <h1>Separating Axis Theorem</h1>
   <section>
+    <p>
+      The Separating Axis Theorem (SAT) provides a way to find the intersection between any <i>n</i>-sided <a href='https://ianqvist.blogspot.com/2009/09/convex-polygon-based-collision.html'>convex</a> polygon or circle. In this tutorial, I will explain how this theorem works, and how you can use it to both detect and resolve collisions in your simulation.
+    </p>
+  </section>
+  <section>
+    <h2>Explanation of Separating Axis Theorem</h2>
+    <p>
+      SAT makes use of vector projection to figure out whether or not two concave polygons are intersecting. The way to think about it is this:
+      
+      <br/>
+      <br/>
+
+      Given two shapes <b>A</b> and <b>B</b>.
+
+      Imagine we could isolate a single edge of A and shine a light on it.
+
+      
+    </p>
+  </section>
+  <section>
+    <h2>Algorithm for Finding the Intersection</h2>
+    <p>
+      Given two polygons <b>A</b> and <b>B</b>:
+      <ol>
+        <li>For each edge on A, get the normal <i>n</i> of that edge.</li>
+        <li>Project each vertex <i>v</i> of <b>A</b> onto <i>n</i>. Return the minimum and maximum projection of all vertices.</li>
+        <li>Repeat Step 2 for polygon <b>B</b>.</li>
+        <li>If the min and max projections found in Steps 2 and 3 do <b>NOT</b> overlap, the polygons are not intersecting. Return false.</li>
+        <li>If the projections overlap for each edge of both shapes, the shapes are intersecting. Return true.</li>
+      </ol>
+    </p>
+    
   </section>
   <section>
 	<h2>
@@ -83,12 +115,13 @@
         Stop
       </button>
     </div>
-    <footer id="references">
-      <h2>References</h2>
-      <ul>
-      </ul>
-    </footer>
   </section>
+  <footer id="references">
+    <h2>References</h2>
+    <ul>
+      <li><a href="https://en.wikipedia.org/wiki/Vector_projection">Vector Projection Wikapedia</a></li>
+    </ul>
+  </footer>
 </article>
 		</main>
 	</body>