Motion and GPU
I am teaching myself Motion today (my background in basic compositing is FCP if I could get away with it, or AE, especially when I'm not working in an FCP setting).
I came up against a 2048x2048 wall, so I came here and learned why this was the case through the archives. Motion doesn't like to deal with anything bigger than 2048 in any one direction with the graphics card I am using.
I guess this leads to two questions:
1) How do people get around this? I am trying to scroll left-to-right a series of magazine covers that I initially compiled in Photoshop, on separate layers... essentially, I tried to import a 320px x 3100px @72dpi PSD. I know that FCP would be grumpy about this sort of thing, but it would put up with it grudgingly if I moved slowly and rendered it into a QT file as soon as I was done. And because the covers are separate Photoshop layers, I suppose I can break the covers into separate Motion layers, and then try to apply the effects I wanted to apply to all the covers individually to each smaller group... but that just seems backwards, since they're all supposed to be working together.
2) This is all happening at work on the company's G5 PowerMac, with a ATI Radeon 9650. Meanwhile, I just bought myself a 17 inch Macbook Pro to do personal projects on the side. It should arrive someday soon when Apple gets around to shipping it, and it comes with a ATI Mobility Radeon X1600 GPU. I looked, but I cannot find where it would say (or how to interpret the specs I do have access to) what sort of limitations this card will have in Motion. Basically, will it be 2048, 4096, 1024, or something else altogether? And what spec tells me that so I know for future reference?
Welcome to the wild world of hardware-based rendering! Motion is limited by the maximum texture size of the system's GPU. For ATI cards before the X1600/X1900, this limit was 2K (2048x2048). The newest ATI cards appear to support 4K, but I've seen some texture corruption when getting near the 3K point, so I can't vouch for how definite it is. Nvidia GPUs solidly support 4K.
Unfortunately, these numbers are totally up to the GPU manufacturer, and since GPU development is driven by games and most games don't have textures that exceed 1K, it's really rather miraculous that we're seeing 4K at all. Huge texture size just hasn't been that much of a hot issue for game developers. That being said, rumors have been floating around the GPU-geek forums that ATI has a card in development that is capable of 8K. My heart beats fast just thinking about it, but it's just a rumor. Would be sweet, though, eh?
There's a bit more explanation about Motion's GPU limitations and practices here: http://www.motionsmarts.com/tutorials/nutsandbolts/sizematters.html
Tiling (as you described) can get by some of the limits, but it only works if you don't do anything that forces a pre-comp of the layer containing the tiles, since that forces Motion to try to render the entire area (which is too large), resulting in cropping. Again, more on that in the linked article.
Good luck with your project!