Channels (Alpha, etc)

[Fat John]

Can someone explain to me what this channels business is all about? I've started mapping and it seems like important knowledge to have. Thanks in advance http://forums.3drealms.com/ubbthreads/images/graemlins/smile.gif

[NetNessie]

Channels in what?

PhotoShop, Level Editor, Television?

[CronoMan]

8888 - 32-bit RGBA
888 - 24-bit RGB
565 - 16-bit RGB

Red Green Blue Alpha

Alpha maps is commonly used for transparency
As far as I know, PNG is the only image format which supports 32-bit colors (except PSD). Well, Adobe Photoshop also has support for 32-bit BMP, but windows do not.
GIF is paletted, and has a max of 8-bit, where the first color in the palette is transperancy (if enabled)
But the transperancy there is "binary"; on or off.

RGBA is a common 32-bit format
Alpha maps is also used for heightmaps

[Joonas]

Don't you mean 48-bit, not 32? PNG supports 48-bit colours (more than any modern monitor can show).

[CronoMan]

48-bit? is that 16-bit per-channel RGB?

[Fat John]

I mean texturing in HL2. I thought htat understanding all this channels business would be helpful in the long run.

[DudeMiester]

You know how array can have multipule elements, well just pretend that array is your colour, and those elements are each a channel. Each channel represents something, R, G, B, Alpha, Height, Depth, etc. Can be whatever you want. Also, the amount of data used in each channel can differ from the other channels.

[Night Hacker]

CronoMan said:

As far as I know, PNG is the only image format which supports 32-bit colors (except PSD). Well, Adobe Photoshop also has support for 32-bit BMP, but windows do not.

Alpha maps is also used for heightmaps



I believe Targa's (.TGA) support Alpha channels.

[DudeMiester]

TIFF does too I believe, and it does floating point too, which is excellent for HDR images.

[Alcoholic 007]

8 bit! - 255 + 1 blank alpha channel colors! :-D :-D :-D

WHooo!

(it's what tirbes used!)

[Night Hacker]

8bit doesn't have an alpha channel. The first index in the palette is a transparent colour. It can be anything, it will never show and it doesn't effect the level of transparancy like alpha channels do. It is simply 100% transparent.

An interesting note, Age of Empires used 8bit.