Question on " DXt1 with alpha" support.

[Guest JohnC]

I was told on another GMAX Forum that DXT1 with alpha file formats was not supported in FS9 and that I would have to stay with DXT3 for full and partial transparency. I hope someone more experienced can confirm this is not true.

[Guest artmartin]

From what I understand the DXT1's will only support areas of full or no transparency. The DXT3 is the only format for displaying partial transparencies. Other than that they're completely compatible with the sim. DXT1's with alpha sure work for me.Art

[Guest JohnC]

Yeah, me too but I'm having some problems with a custom scenery that go away when I empty the texture folder. FS9 switches to a mip map less than 8 on ground textures if I use >160K BGLs, if the bldgs are textured.One should have more room than that, especially since I have a high end system with 1 g of RAM. Thanks for the input. Sometimes code will work even when "not" supported.

[rhumbaflappy 113]

DXT1 has a singular alpha channel, but it is not restricted to black on white. That alpha channel can have a full range of greyscale... 256 values between black and white. And that should give you a full range of transparency.I'm not sure what this does to photoreal textures, but I suspect a "breakpoint" value that determines water.Dick

[Guest JohnC]

Thanks, I'll look into this further...DXT1 takes up half the space of DXT3.

[arno 1]

Yes, DXT3 is indeed twice as big, due to the 4 bit alpha channel, while DXT1 only has a 1 bit channel.And what do you mean with the mip/distance problem? Do you get blurry textures on the ground? This has probably not too much to do with the BGL size itself, but some other problem in the BGL file.

[rhumbaflappy 113]

Hi all.Bad news. It seems DXT1 forces a simple black and white alpha channel.8-bit with alpha, DXT3, and others allow a greyscale.And now we know why DXT1 is smaller in size than other formats. If you use 8bit with alpha as a Custom texture for terrain, the alpha behaves just like DXT1, with the land/water cutoff at 50% grey.So, for objects, the texture should probably be DXT3, if you require varying transparency.Dick

[Guest JohnC]

Hello Arno...my blurry texture problem is gone, and I find I have once again been bit by my use of a stored flight getting corrupted somehow, although it took longer this time. I use a stored flight to go immediately to a specific viewpoint when I am debugging gmax structures. My stored flight lasted a couple of weeks then got corrupted, and it took me a while to realize it. I'm going to try making stored flights a read-only file next time, and see if that works.

[Joe W 0]

If there is just one 8 bit, 24 bit or any other texture mode in there you will get the blurries. That includes ships and other AI craft. If you go with a DXT format...... all need to be that format.Been there.Joe W.

[Guest JohnC]

Joe! thank you for the hard won experience....I will check on this....I hope that this does not include FSSC runway, etc. textures OR I can use DXT1 in FSSC taxiways,runways,etc.

[Joe W 0]

Only thing I have to say is ..... try it.it might work.But if the blurries strike..or you get a seveare frame hit.... try going all DXT format or all 8 bit.Joe W.

[Guest JohnC]

Interesting thought...I don't get frame hits ever that I can see, butit seems that the number (or format) I have is close to or over some FS9 limit. Unfortunately, I believe some of the textures used (on the plane itself, for instance are not in DXT format.