I have Samsung plasma in the bedroom that supports 3D. However its one of the last years models and it only supports 1360x768 resolution in 3D. No problemo...works good with PC games running at that resolution.

However I can't get it to work with the 360 due to the fact that 360 will not give me 1360x768 over HDMI. I can do it with a VGA adapter, but Avatar and Legend of Han (the 2 3D games available for 360) require HDMI to do 3D.

Does anyone know a way to force HDMI in to custom resolution of 1360x768? I managed to do it once...somehow when I was going in to "set resolution to optimal" but that hasn't worked since...

The "set resolution to optimal" was the only thing I was going to suggest you try,  as I see you already tried that.   I dont think it is possible an set a specific/non-standard resolution as the only output.   What is the max non-3D resolution on the plasma,  if its any different?  Cause if it was the same 1360x768  I would think just setting the 360 to maximum output would work.  

Could you set it to 720p, and still get 3D?  If the TV supports 3D at 1360x768  it should be able to do 3D at 1280x720,  which I think the Xbox 360 can force.

Sadly the TV only works at 1360x768 or 1024x768 when it comes to 3D. Every other resolution is like a kick in the balls to the 3D feature. It just knocks it off and switches to 2D. Has to do with the whole checkerboard pattern supporting only specific res...

Its no big deal as I have the Samsung LED DLP in the other room which looks much better @ 1080p 3D...but kind of a shame since I have to hack Nvidia 3D vision to work with the 360 which takes a few minutes or unplug it and plug the other generic glasses. That TV isn't the easiest to manouver around ...:)

BTW, can PS3 set specific resolution with HDMI, 1360x768 to be exact? If it somehow magically supports the checkerboard or side by side 3D formats, I may be able to get some 3D PS3 gaming in the bedroom...

No,  the PS3 cant do it either,   it has the standard 480P/720P/1080i/1080P  selections.   

After a quick look on google it seems that if you connect the vga and hdmi cables it will let you choose vga res for hdmi, or use a hdmi-dvi adapter and run seperate audio. Either one might work.

Thanks man...I googled this many times but these ideas did not come to me. I guess your google is better than my google :)

For the second suggestion, id have to run HDMI-DVI cable in to DVI to HDMI converter then in to the HDMI port on the TV. I'll try it but i am not expecting it to work... But the VGA HDMI suggestion has a pretty good chance of working. I'll try that too after I order a cheap pair of VGA cables. To get both cable plugged in you have to destroy the plastic casing on your VGA plug as it covers the hole for HDMI cable

Next time try Bing... it will usually deliver you better results for something that specific