-the "main" redner target-the one that uses the swapchains buffer-this is the same resolution as the screen

-the render target that is than applied to a fullscreen quad-the same resolution as the screen

-the low-res render target-half the size of the screen

This is how I use them:

1st I render everything (scene) to the fullscreen quad render target (the one that is the same resolution as the screen)

2nd I set the half-res render target and render the fullscreen quad with the texture that was rendered in step 1

3rd I set the "main" render target and I render the quad with the half-res texture

The problem is that it looks like that only the upper-left quad of the entire screen is shown.

Does anyone have any ideas why this is so?

I recommend using PIX or NVPerfHUD (if you have a nvidia GPU) to check if your first or second transfer goes wrong.

Beside of this posting some of your code may help.

When you change the render target, make sure you change the Viewport property to match in width/height.