Drawing a geometry buffer with alpha enabled?

[Stefan Lundmark]

I'm trying to get a GeometryBuffer to be drawn with alpha enabled, ie the textures that are transparent should be when they get rendered.
Currently they're showing up white where they should be showing the background.

Let me know if this is too vague, I just haven't found any documentation regarding this.

Edit: Turns out it's OGRE setting the texture format to X8R8G8B8 (which AFAIK is padded without alpha?). Not sure why it does that but oh well, thanks to those who have read.

Another edit: OGRE doesn't like TIF's that contain alpha, that's for sure. Converting the file to a PNG works wonders, but that's not really a solution. Going to mention this on the OGRE forums.

[Jamarr]

So you are saying the TIFF loader for OGRE doesn't support alpha? That seems odd since the TIFF format has been around for quite a long time. Thanks for the heads up though.

[Stefan Lundmark]

So you are saying the TIFF loader for OGRE doesn't support alpha? That seems odd since the TIFF format has been around for quite a long time. Thanks for the heads up though.

LibTiff doesn't like the garbage that Photoshop sometimes can produce when writing TIF files with layers or metadata. It's part of the "BIG-Tif" specification but I'm not sure they implemented all that in the stable release yet. I know there was the same issue in another engine, but I thought we worked around it. Guess not.

If I query LibTiff directly and ask how many samples per pixel the TIF picture has, it says 3 while it's clearly 4. Must be that Photoshop is baking the alpha into a second channel or something. I have no idea, I'll use FreeImage's PSD support for now instead.

[Jamarr]

I see. Well that makes some sense then, as the BigTIFF specification was only recently released (2007) and I believe that the LibTIFF support for it is still in beta and has not been made official yet. So you may want to avoid that format until your image library has released official support for it.