I'm really surprised no one has thought of that before (or even if they did - I've never seen anyone use this trick in their maps) but
there actually is a great and easy way to make smooth semi-transparent fades with BMP sceneries instead of PNGs. The key is having a bmp scenery so small that when you stretch it - it becomes blurry. I used them in many of my remakes and they work great so far. I've attached a scenery pack to this post.
Consider this as a New Year present from me. <3
As an example, here's a BMP-only version of inf_SunRise before I used BMP fades:
And after:
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Known issues:
- It's doesn't fade as color-transparency. It fades as color-SemiTransparentBlack-transparency. So you'll get a little bit of a dark shadow around the scenery, but it's barely noticeable and sometimes actually looks better this way.
- If stretched too much - it looks a bit pixelated for some people. I'm not sure what exactly causes it (looks perfectly fine for me) and if it occurs with PNG sceneries too. Here's a screenie VirtualTT showed me: http://img121.imageshack.us/img121/2605/20091223235325.png
Just avoid stretching those sceneries to ridiculous sizes