Ahhh.
Ok.
Always "work in" 24bit color (16 million). Now, PSPX introduces new terminology. They call it 8bits per channel. There are 3 color channels (red, green, and blue). So, 8x3=24. Save your masters that you work on in either PSP's *.pspimage format, or photoshop's PSD format. This retains all the layers.
Your output format from any paint program should be TGA, 24 bit. The Mask Layer (sorry, I'll call it Mask Layer), should be BMP, Greyscale (256 shades of grey). Normally, you do NOT want to save as 32 bit TGA (which is the 24 bit image with the embedded 8 bit mask). This is because in the BMP tools, you specify the mask to use for a particular texture as a separate image file.
An Alpha Channel is a place where you can store selection data, masks, etc. So sorry for the confusion. You can store "masks" inside alpha channels. For FS2004 purposes, you will have a mask that is a separate image. It's like a digital pocket(s) of an image.
FS2004 supports images of different bit depths and some of those image formats support alpha channels that contain a mask.
This mask, again, depending upon the image format can be:
DXT1 = 2 bit (black or white)
DXT3 = 4 bit (16 shades of grey)
DXT5 = 8 bit (256 shades of grey)
All of these formats I believe are 16 bit color (16,384 colors)
Some of the 888 format BMP files can be 32 bit (24 bit RGB + 8 bit Mask)
Or, you can use a full-blown, uncompressed, big-ass 32bit BMP.
The different formats allow for faster texture loading at a cost of image quality (less bits per pixel for color representation); however, for the most part, the end user will NEVER even notice.
I assume you have FS2004's bmp tools? If not, please let me know. You absolutely need this to work in the texture formats that FS2004 supports. This program also generates mip-maps for you when you save, so that the further away the aircraft, it "shifts gears" to a lower resolution texture (MIP).
e.g.:
1024x1024 -> 512x512 -> 256x256 -> 128x128 -> 64x64 -> 32x32 -> 16x16 -> 1x1
7 mipmaps for a 1024x1024 image. Increases filesize, but is nominal.
These mips can be embedded in the extended BMP and usually is a good practice.
A Mask is a 256 greyscale image. Those 256 colors from white to black represent how much "shiny effect" (usually) is applied to the corresponding areas of your texture. Depending upon the model, those 256 shades of grey represent the opacity level of the texture. White being fully opaque, black being fully transparent.
Literally, it's like Digital Masking Tape. Hence the name "mask".
TIP:
Since you have to have a separate mask image the same size as your source texture, in PSPX, it was difficult for me to figure out how the heck to save the mask as a separate image.
The work around:
- Drag the Mask Layer to a blank space in your work area to create a new image
- Adjust this image to Greyscale
- Fill the raster layer with BLACK
- Merge all
- Adjust Image -> Negative Image
- Save as 8bit BMP