I created a scene for an animation by painting in photoshop meant for HDTV 1080p. I scaled the image down in order to create a longer panel for a tracking shot, but now when I scale it back up to the correct size the resolution is terrible! Is there any way to restore the resolution? I was told I should have made it a smart object before resizing, but is there any way to fix the problem after the fact?
Assuming your painting is made of pixels (vs. shapes), other than going back in your History (assuming you're in the same Photoshop session), no. Once you've downsampled pixels, there's no getting the lost detail back.