DXT uglyness problem

[GIdenJoe]

Hello there, for the ppl that know what I am working on, they will know that I am making lightmaps for my meshes.

But now I have encountered a technical problem that is making the lighting a bit less visually attractive.

When I import the lightmap in ued, there is no problem, everything looks ok but when I dxt1 compress it, it makes the light fallof area's on the lightmap a bit ugly. You can see dark green circles in it and I don't know how to fix that. Also for the record, I do not have any knowledge of photoshop and I don't have the software itself, so for me it is not an option.

[FBMachine]

Are you using an nvidia gfx card? When nvidia cards decompress DXT1 textures, it does it in 16bit which is probably where the greening ugliness is coming from because of the loss of precision. Using DXT5 instead would fix that if that's the case, but then you'd have somewhat larger lightmaps. If you don't have an nvidia card, it might be that the texture resolution for the lightmaps are too small. Other then that I can't think of anything.
Dan

[GIdenJoe]

I have an nvidia geforce2 gts pro :)

So erm (without using dxt5) coz the level is already 10 megabytes how do I work?

[Scourgem]

You... don't. :p

Converting a grayscale texture will apparently always cause those green outlines to appear - I've had a similar problem with some projectors. DXT5 makes them less visible than DXT1, but they're still there. You probably shouldn't worry about it, though... I don't know about lightmaps, but with projectors you can't really see the green lines ingame. The texture appears ugly in the browser, but looks just fine ingame. Look at the example below (this one is actually DXT1 compressed).

[GIdenJoe]

I'm afraid it actually does show.

http://users.pandora.be/gidenjoe/pix/ut2003/mapping/annihilator/dxtugly1.jpg

http://users.pandora.be/gidenjoe/pix/ut2003/mapping/annihilator/dxtugly2.jpg

And I'm not happy with that result.

[Scourgem]

Ick! I have to agree, that's not an acceptable result at all.

Those lightmaps are simple grayscale images, just like projected shadows, right? I'm experimenting a bit with projectors atm... will let you know if I run into a solution.

[GIdenJoe]

They are not grayscale. They represent the lighting on your mesh so if you have a blue light, the lit area's on the lightmap will be brighter blue. Lightmaps are like a skin that is applied to your mesh and blended with the textures on it.

It's logical even, what if you applied a blue lightmap that is greyscale than the texture would be blended with the grey of your lightmap and would look gray as result :)

Anyway, I'm looking for solutions but don't know If I'll find any. Coz I hope this little thing does not ruin my map.