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How to do alpha cut windows

PostPosted: Thu Jan 15, 2009 9:07 pm
by Viikate
Since there seems to be some misunderstanding about this issue, Magpie asked me to clarify a bit.

For some reason, there was this picture in the original IL-2 tutorial:

It doesn't matter if the color in alpha layer is gray or black, it's always fully cut. You cannot make semi transparent surfaces with alpha layer of skin1o.tga. You can only cut the holes for the window. The actual window is separate surface with the glass material.

If done properly, the alpha cut window/canopy will have three different layers. Outer, inner and the glass between them. Like this:

(Never mind the missing glass panel. It's filled by a separate glass panel that slides back)

Only materials that will be alpha cut are the double sided materials (Gloss2D0o.mat, Gloss2D1o.mat, Matt2D0o.mat, etc...)

Also it's good to notice that you can use the texture space that is cut away. It's not wasted space like you normally see in the skins. Here marked with red color, I have put some small parts to the window "holes"

And the alpha layer of the same texture. Also notice that ALL the holes that the plane will have it painted here.

But of course you could always do the windows/canopy without alpha and actually this is better way. Alpha is just a lazy man's solution (but so easy to use) :P Many modellers doesn't even stop to think that rendering one alpha cut poly is way more slower than rendering one without alpha. I recall that some MG guy once told me what this exchange rate is in IL-2 engine and I was suprised how big it was. Can't remember it anymore though...

PostPosted: Fri Jan 16, 2009 6:29 am
by magot
yes useful info for public .... as I know more people know use only alpha channel for glass effect.
Is easy build separate material,basic ID of glass was used to number 30,and use Oleg texture called glass in folder TEXTURES.When are used 4 layers this material is possible have a shadow glass effect.


PostPosted: Fri Jan 16, 2009 3:59 pm
by asheshouse
Thanks Viikate. A very useful mini tutorial