Why use Extended Bitmaps?

[asimmsjr]

This may seem like a dumb question and since it relates more to EOD it may not belong here exactly but this seems to be the best place to get scenery design answers.

I am using EOD to design various objects for Airport. I am using 256x256x256 8 bit bmps for textures taken from photos. They seem to work whether I convert them to extended bmps with BMP 2000 or not. If there are no transparent textures or even if there are, what is the reason for the recommendations to use extended bmps?

Thanks,
Al

[shakakoz]

There's a few good reasons:

1. extended bitmaps allow you to use more colours. This may not be an issue for you, but if you are manipulating the image using PSP (or photoshop) you need those extra colurs to use some of the effects.

2. The DXT 1/3 format is one that is optimized for your DirectX-compatible video card, thus improving framerates (hopefully).

3. extended bitmaps allow the use of the alpha channel, which can provide either reflectivity or transparency. If you have any grid or lattice work to model, then alpha mask can make parts of the model see-through. Although the use of transparency may cause a slight loss of framerates, this would be ofset by a drastic reduction in the number of polygons needed.

4. extended bitmaps allow you to use mipmaps, improving framerates.

If you have a small project, that isn't too complicated, then you might not need to use the extended bitmaps. But the extended bitmaps aren't too difficult to use, and they will improve performance a little.

- Martin

[asimmsjr]

Martin,
Thanks for your answer. I won't pretend to understand all that you have said but my project is very large and complicated and I am using extended bitmaps - was just curious why after finding that they worked when forgetting to convert one. I knew that it had not been converted because an area that I had defined as transparent was not and that was the reason. So far I have managed to stay with 256x256 bmps but I do convert them all to extended with BMP2000.
Al