Hello my game BG1 from GOG runs fine on 32bits, except for the fog glitch that makes the edges of the fog triangular/weird shapes. When i switch to 16bit / mirror it fixes the fog but the game slows down drastically.

My computer is i7, windows 8.1.

Is there any way to fix the fog without slowing down my game?

You should not need any of the 'BLT' options (mirror etc.) on a modern computer. Switch all BLT options off and return to 32 bit, then run config.exe inside your BG folder, and make sure you have a cache of 768 MB, and your game speed is set to default (30).

Also, make sure you do not have your game installed inside of the Windows' protected 'Program Files' folder structure.

Reinstalled BG to test this - I too have to use the software mirror BLT option and 16-bit colour to avoid flipped fog segments, even with the config options set as you described.

I don't get any slowdown with software mirror BLT enabled, though.

Windows 7 64-bit
Nvidia GeForce GTX 770 with latest drivers (334.89)
Intel Core i7 4770

The need to have the BLT option/s enabled is probably some kind of incompatibility with modern GPUs / drivers / OS.

EDIT: note, I'm using the CD version of the game

I run BG1 (GOG version) on 32 bit, no BLT options, no slowdowns, and no fog issues on 2 separate systems:

Windows 7 64-bit
Dual Nvidia GTX 580
Intel Core i7 3960X

Windows Vista
ATI HD 4870
Intel Core 2 Q6700

Over the years I've never had to enable any BLT option, and I've never had to resort to 16 bit. Go figure.

Ok i reinstalled to the C;\ atari and it still has the same problems.

BG1, BG2, IWD1, IWD2 have the same problem. Except the rest are fixed by 3d acceleration but when 3d acceleration is turned i can only play the game in a small box with the rest of the screen blacked out.

What is your hardware? And do you have Intel integrated graphics?

I have i7 4770k, nvidia gtx 780, windows 8.1, 8gb ram. I tried all sorts of tweaking the graphics card settings for baldurs gate, i also tried taking out the video card and using just the onboard hdmi with my motherboard and it works the same as with the video card in.

I do have intel integrated graphics as well as nvidia.

Intel integrated graphics chips tend to wreak havoc with some games, on some systems. Try disabling the onboard chip in your BIOS -- if you're not sure how, your motherboard manual should tell you how. There's nothing wrong with your BG installation, since you're having the same issue with BG2, IWD & IWD2. Assuming it's not a Windows 8 issue, the Intel graphic chip is the easiest to rule out.

I dont have intel integrated graphics i dont think....i searched the bios and found nothing and all my control panel options

See, now I'm confused. First you say you have Intel integrated, and now you don't? Which is it?

As I said, read your motherboard manual: all BIOSes have the capability to disable onboard graphics. You should see something like 'PnP/PCI configuration', and this will have 'Init Display First', or something similar. This should be set to PCIEx as primary. The options may be named differently, or you may even have to set a jumper on the motherboard, and this is why you must read your manual.

I've had the integrated graphics on my 4770 disabled since I built my PC, and still get the fog issue.

I seem to remember also having the issue when I installed BG on some older hardware a few years ago:

Windows 7 64-bit
Nvidia GeForce GTX 460 (driver version mid-late 200's to early 300's.. maybe)
Intel Core 2 Extreme QX9650

Maybe a driver setting is interfering with the game? I'll mess around with some and see what happens.

EDIT: No luck with driver settings. Also tried various compatibility modes and settings, which either had no effect or made the game crash on launch.

its a windows 8.2 problem....is there any tweaks to windows 8.1 i can do?