Trying to create a skybox, problem with brightness (solved)

[skyscraper]

Hi folks!
I'm rather new to Terragen 2 so I may not know all the tricks.
I'm trying to create a skybox (5 images, no 6th (bottom) image needed) for Half-Life 2, but all rendered images have slightly different brightness. 
That causes ugly seams visible in the sky.
Is there anything I can do to force exactly the same brightness to all rendered images?
I'm creating them with camera angles at 0, 90, 180, 270 degrees horizontally, and top image 90 degrees up. 270 degree image often tends to be darker than others.
I'd appreciate any help that could solve this ugly problem.

EDIT:
I took a screen shot:
http://www.chictrinity.com/pix/hl2_skybox1.jpg
The game looks 1000x prettier with the new sky, but those box seams ruin everything. There has to be a way to remove them.

[Tangled-Universe]

Welcome to the forums SkyScraper.

I'd strongly suggest using the search function on these forums.
This question has been asked dozens of times before and there's really a lot of info out there.
More FAQ are covered here:

http://www.nwdanet.com/terragen-tutorials/63-terragen-2-faq

Here a some results of a search on these forums which discuss seams in lighting and how to fix it:
http://www.planetside.co.uk/forums/index.php?topic=14504
http://www.planetside.co.uk/forums/index.php?topic=14355
http://www.planetside.co.uk/forums/index.php?topic=14246
http://www.planetside.co.uk/forums/index.php?topic=15051
http://www.planetside.co.uk/forums/index.php?topic=13453

In contrary to the FAQ, which I should update some time, these results discuss the use of a GI cache.
Currently this is the best way to get a good skybox.

Cheers,
Martin

[skyscraper]

Thanks
Sorry, I didn't know what to search, I tried with "brightness", found nothing.

Well, my problem is still there, and another one came up. I tried to change GI settings, and now I can't render anymore. Images are only dots on black bg.

http://www.chictrinity.com/pix/tg2_wtf.jpg
Can't render a decent image anymore, I don't know what happened.

If you don't care too much about GI:
Use a fill light setup.
You can find a basic fill light setup here: http://forums.planetside.co.uk/index.php?topic=580.0
When using a fill light setup make sure to disable the "Enviro Light" node and to set both GI relative detail and sample quality to 0 to completely disable GI.

I downloaded "fill lights.tgc" file, but where do I put that file? I have no clue...
And what/where is "Enviro Light node"?

[Oshyan]

Please reference the GI cache documentation here:
http://www.planetside.co.uk/wiki/index.php?title=Terragen_2_Global_Illumination#Rendering_with_GI_cache_files
You are in "GI cache write" mode so *only* the GI cache will be generated, that's why you only see dots, that's the result of the GI cache. Once your cache file is generated, you need to switch to "read GI cache file" and specify the name of the file you wrote your cache to.

The Fill Light approach is completely different and will change the look of your scene since you are no longer using Global Illumination. With the availability of GI caching, I would not suggest the Fill Light approach unless you still have problems even when using GI cache.

- Oshyan

[skyscraper]

Thanks a lot! It solved my problem. Saving cache file once (one per skybox), and reading it for the rest of the images works fine, no more seams in the sky.