added coordinate system documentation (in progress)

git-svn-id: svn://anubis/anaglym/trunk@273 99a6e188-d820-4881-8870-2d33a10e2619

doc/index.html

@@ -26,6 +26,7 @@ The library functions are documented below.
         <ul>
             <li><a href="#invocation">Invocation</a></li>
             <li><a href="#colors">Colors</a></li>
+            <li><a href="#coordinates">Coordinate Systems</a></li>
         </ul>
     </li>
     <li>
@@ -69,6 +70,21 @@ consist of red, green, and blue components.
 Each component is a real number that can range from 0.0 to 1.0.
 </p>
 
+<a name="coordinates" />
+<h3>Coordinate Systems</h3>
+
+<p>
+Anaglym uses the OpenGL right-handed coordinate system for its 3D coordinates.
+The default orientation is such that the XY plane is horizontal (the
+"ground" plane).
+The Z axis extends positively into the "air" above the XY plane, and the
+default gravity vector pulls along the negative Z axis.
+</p>
+<p>
+FIXME: 2D coordinates
+</p>
+
+
 <hr />
 
 <a name="ag" />
@@ -208,7 +224,7 @@ of the circle.
 
 <a name="ag_drawImage" />
 <h3>drawImage</h3>
-<p><tt>ag.drawImage(width, height, x, y, texture, [, rot])</tt></p>
+<p><tt>ag.drawImage(width, height, x, y, texture [, rot])</tt></p>
 <p>
 This function tells the engine to draw an image to the screen.
 <tt>width</tt> and <tt>height</tt> specify the size of the image,