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DXTBmp alpha channel

Mr.Crocodile

Mr.Crocodile

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243
Country
italy
Hi guys, probably the most of you could smile for this apparently stupid question, but after a good period of time passed using DXTBmp to prepare my textures I noticed a thing to which previously I did not get enough attention.
In particular I would like to understand better what the "apply alpha to image" command is for. I prepared the texture, imported it in DXTBmp and created the alpha channel using Alpha -> Create alpha template (or the other options). Then I used Alpha -> Refresh alpha and then I save the texture as DXT3. I noticed a little differences of transparency if I use the "apply alpha to image" or not before exporting the texture as DXT3, but I do not understood exactly what the command does.
In particular the reason for which I decided to ask your help is a fact happened this morning:
I prepared a double yellow strips. I would like to obtain a little transparency of the yellow when applied over the asphalt so I created an alpha channel using a grey value of 100 for the part related to the yellow and a value of 0 for the part of the texture that could be completely transparent (the part between the two yellow strips).
Clipboard01.jpg

Without using the "apply alpha to image" the transparency works quite well except for a very thin white line appearing on the border of the yellow lines (It persists even if I change the "Texture_max_load" parameter in my FS9).
Clipboard04.png


If I use "apply alpha to image" instead I obtain that the lines become grey, but the white thin border does not appears.
Clipboard03.jpg

The strange is that when I use "apply alpha to image" the main image become all grey like the image I attach
Clipboard02.jpg


What I did not completely understand?
 
As you note, you basically get what you want if you are not using the "apply .. to" process. In order to have better control over the alpha I would suggest to use your paint program to create the alpha as a grayscale image. Begin with a copy of the diffuse. Color those sections that you want to be semi-translucent as grey, and those that you want to be entirely transparent black. Then, back in dxtbmp, import the alpha layer (now fully controlled by you, not some default process) and save as dxt3. If the white borders persist, either increase the yellow area in the diffuse, or the black area in the alpha.
 
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