Freeflight Design Shop Forum

Mini-Tutorial: Alpha Channels in PSP

Posted by Tom Gibson/FFDS on Wednesday, 11 December 2002, at 11:24 a.m.

Hi all,

Here is something I wrote up for others; thought it might help those working with the new FSDS2 Lightmap options:

Load your daytime BMP file into Paint Shop Pro. In PSP, alpha channels are manipulated as Masks, so go to the Mask menu and select New Mask/Show All. In this way you will create an all white alpha channel (no transparency, which will convert to no reflectivity in FS). Go to Masks/Edit Mask. Now you will have a gray scale in the palette window, and you can "paint" the Mask in varying shades of gray. The darker the gray the more transparent the Mask and the more reflective that area will be. I often do a Magic Wand selection of the bare metal textures (before all this Mask business), and then when I get to this point I do a fill into the Mask of how reflective I want the bare metal to be (grays of around 212 to 240 usually give good effects, but you'll want to experiment yourself). Now you will see varying amounts of transparency (checkerboarding) in the image. The areas that will be more reflective in FS will be more transparent.

When you are happy with the Mask, go to Mask/Save to Alpha Channel. Select the existing Alpha channel (if any) and delete it. Then OK back out of the dialog boxes (you don't have to give the new channel a name). Finally, go to Mask/Edit Mask, Mask/View Mask, and then Mask/Delete Mask. DO NOT merge the Mask with your image!

Now save the repainted TGA file, and reload into your BMP program. Save as a BMP file in DXT3 with Alpha format, and that's it! I keep the TGA files as my source files.

When you want to edit the alpha channel in your TGA file, use the Mask/Load from Alpha Channel menu. You will see a thumbnail of the alpha channel in the dialog box. Click OK. Now edit the Mask as described above.

For the night textures, they are handled exactly the same way, but they should be all black except where you want lighting on the plane. If the alpha channel is white in that area, the lights will be visible only when the landing lights are on. If it is black, they will be visible whenever the panel lights are on (windows, etc.). I add things like curtains, etc. to the lit window textures to simulate the light shining through them.

Hope this helps,


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