DX Projection Matrix.

Can anybody explain how Mark is using the Projection Matrix?
This is what is set :

		matrix=[..
		2.0/gw,0.0,0.0,0.0,..
		 0.0,-2.0/gh,0.0,0.0,..
		 0.0,0.0,2.0/depth,0.0,..
		 -1-(1.0/gw),1+(1.0/gh),1.0,1.0]

with gw being graphicswidth(), gh is graphicsheight() and depth = 2.0.
I've read the DX7 doc for Projection Matrix and can't tally the settings with the values Mark is using.
Anybody know what's happening?

matrix=[..
         sx      ,0.0      ,0.0         ,0.0,..
         0.0      ,-sy      ,0.0         ,0.0,..
         0.0      ,0.0      ,2.0/depth   ,0.0,..
         -1-(1.0/width),1+(1.0/height),1.0,1.0] 

sx and sy are the matrix position or camera position (in your case the camera is pointed directly at the center of the view), depth = depth of view (only objects within this depth will be rendered). height and width are the size of your view on the world.

Thanks Tim.
In D3D7Max2D the viewport is set with gw/gh.
I guess the camera height and width is creating a smaller view of that viewport. Is that right?
If so, what is the benefit and why -1-(1.0/gw) which seems a tiny amount.
I might even be looking at the wrong thing.
I want to be able to create a camera and rotate it with the correct aspect ratio as well as zoom. I have got some way to doing that.
Any ideas on this?
<edit> I have RTT working now and it was nothing to do with the matrix... my mistake.