Can't find the correct way to compose. Please help!

[RSF]

Hello!
I'm trying to composite this simple scene but still didn't found the right way to do it?
Here's the result I managed to get:



In this case I used the gbuffer channels. Multiplied and added the difuse, raw light and raw GI for each image (one with the red objects the other with the blue box) and composed the two using the alpha channel.

As you can see there's a problem with the alpha and another with the sobreposition of the shadows.
Still have no clue how to solve this?
How is this supposed to be done??

Thanks?

[Morbid Angel]

answer is simple....you have rendered the blue box separate from the other's that is why the tall red box is casting shadow which falls in behind the blue box. If you use gbuffer pases you can render all objects together. Or if you need to render the blue box separetly then you need to include it in the shadow computation of the red boxes pass. Basicly this can be done by using object properties visible to camera and cast/recieve shadows options.

[cpnichols]

Also the black outline around the blue box is probably the fast that you need to pre-multiply the alpha of the blue box before doing the over.