Modeltexturemaker forces transparency on textures extracted from VTF

[GarompaEstomper]

As the title said. When porting something from Source to GoldSRC, I've used VTF edit to extract files as bmp and then pass them through Modeltexturemaker to just index them, but some of them, not all, are then detected as having transparency for some reason when they do not have that, painting 90% of the texture in 0 255 0 blue destroying the entire texture

[pwitvoet]

Some vtf files store their specular mask in the alpha channel, and VTFEdit includes that alpha channel when exporting to bmp. Most image editors won't show any transparency, because the general assumption seems to be that bmp's can't or won't have transparency, but it is there. If you open those bmp files with https://www.photopea.com/ (or if you export as png instead) then you'll see why those textures will become mostly transparent.

The solution is to remove those alpha channels, for example by converting those bitmaps to 24-bit. Alternately, you can tell ModelTextureMaker to 'ignore' the alpha channel by creating a plain-text modeltexturemaker.config file in your images directory, and adding the following line to it: * transparency-threshold: 0. If you do need transparency for some textures, you can add the following line for each such texture: texturename transparency-threshold: 128 (replacing 'texturename' with the name of that texture, without file extension).

[pwitvoet]

I investigated this some more, and it turns out that VTFEdit creates bitmaps that use 'BI_RGB' compression, while most image editors only recognize transparency in bitmaps that use 'BI_BITFIELDS' compression.

Ideally, VTFEdit should export the 'right' kind of bitmap, and it should only export the alpha channel if it's actually used for transparency, or it should let you choose which channels to export (such as RGB only). But I don't think VTFEdit is still being maintained, so yeah.

The image processing library that I use does recognize the transparency in 'BI_RGB' bitmaps, but if most image editors treat these bitmaps as not having transparency, then I think ModelTextureMaker should also ignore the transparency.