Greyscale in photoshop for terrain files

Not sure this is the correct forum for this but here goes.

I'm trying to create a .raw terrain file in photoshop.

My dificulty is using the greyscale nesasary to draw the terrain. I don't know how to do it from RGB and create the 256 different grey shades.

If anyone can help i'd be grateful

Thanks

Not having made a terrain file, I'll just addess making a grayscale in photoshop.

Set the image mode to grayscale (image>mode>grayscale) and use a black brush with only partial opacity to build "organically" up from white. Invert the image if white corresponds to high altitude and black is low.

The image mode isn't the issue. Leave it on RGB (8 bits per channel).

For RAW terrain files, you'll be editing channels. Channels, by definition, are always grayscale. Simply go to the Channels Palette, activate the channel you want to work on, and you'll see that your color palette automatically changes to grayscale.

And, Malik, just so you know, 256 is always the number of values available for any single channel (provided you're working at 8 bits per channel, which you nearly always should be for all things). Wanna know why RGB is commonly described as supporting "over 16 million colors"? It's because RGB consists of 3 color channels (Red, Green, and Blue), each of which has 256 possible values. 256 x 256 x 256 = 16,777,216.