dual channels
Hey PAKMN;
Near as I can figure, the source of your confusion comes from thinking that 2 channels needs to = 2 files. No wonder you're confused when the Displace filter only lets you load one file!
There are a couple of ways to accomplish bundling 2 channels into one file. You indicate you have already had success with a single channel D-map, so we're already ahead of the game.
Option 1 is Stoker's preference - use an RGB file and just ignore the presence of the blue channel. Fill it with 50% gray if you want, leave it alone if you want. Whatever - Displace will pretend it doesn't exist. If the channels palette isn't already visible, choose it from Window>Channels. It it's an RGB file you'll actually see four items: the composite (RGB), and then Red, Green, Blue. There you go - multiple chnnels, one file.
Option 2 is to create a grayscale image - either from scratch (File>New, choosing grayscale) and then clicking the new channel icon at the bottom of the channels palette.
Option 3 is to start with either a grayscale or an rgb file and choose Image>Mode>Multi Channel and then again click the new channel icon.
(BTW - if you highlight a channel in an existing file, choose "Duplicate Channel" from the flyout menu top right channels palette and select "new" as the destination, multi channel is how the new file comes into the world! This is in fact pretty useful if you have a source image you want to use for the distortion.)
However you do it, you wind up with a single file containing (or at least capable of containing) more than one channel. This should be saved as a psd file, and becomes the one file to load in the Displace interface.
Final note, and a VERY critical one if you are following along with Stroker's excellent tutorials. Recent versions of Photoshop have an obscure little checkbox in the preferences settings: Preferences>File Handling> "Always Maximize Compatability for Photoshop (PSD) Files"
Wow. That's a mouthful, isn't it? What does it mean? It means in addition to whatever layers you may have created in the PSD, Photoshop invisibly saves a FLATTENED version too. Okay - what does THAT mean? There is good news and bad news. The bad news is - the saved files are bigger than they need to be, 'cause they carry the baggage of the flattened data. The good news, from Adobe's position: it means that you have the illusion that InDesign will actually accept layered PSD files. :\ The REALLY good news, if you work like Stroker, is you can create a VERY complex, layered psd file (including complex curves adjustment layers) and it STILL behaves itself as a D-map. Took me the LONGEST time to figure out how he could get layered files to work and I couldn't. Turned out stingy me was set to minimize file size, while he was set to maximize flexibility and to hell with file size. Whatever. Just thought you should know.
Hope that helps turn the light on!
Steve