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ryan20fun

can somebody clarify this

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Hi Everbody.

can somebody explain this, im not too fimilier with the different d3d formats.

i was browsing some documentation about finding a suitable d3d format and is saw this

[quote]
Full-screen applications should not specify a DisplayFormat that contains an alpha channel. This will result in a failed call. Note that an alpha channel can be present in the back buffer but the two display formats must be identical in all other respects. For example, if DisplayFormat = D3DFMT_X1R5G5B5, valid values for BackBufferFormat include D3DFMT_X1R5G5B5 and D3DFMT_A1R5G5B5 but exclude D3DFMT_R5G6B5
[/quote]
from here
[url="http://msdn.microsoft.com/en-us/library/bb174312%28VS.85%29.aspx"]IDirect3D9::CheckDeviceType Method (Windows)[/url]

now why is this ?
is alpha not apllicable to fullscreen ?

Thanks In Advance.

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[quote name='smasherprog' timestamp='1313878593' post='4851739']
Who knows why that is there. It is perfectly valid to specific an alpha channel in the back buffer. I would ignore this, and move on because it doesn't make any sense.
[/quote]

This guy sort of right. But the real answer is that technically there is no such thing as alpha on the back buffer since that wouldn't have any effect when getting copied to your monitor. (What would the back buffer get blended with? Your monitor is suddenly going to turn partially transparent in real life!) Alpha channels only have meaning if they are somehow getting blended with something. In my experience, though, most video cards could care less if your back buffer format is specified as having an alpha channel. The final value of the alpha channel in the back buffer will either never be written, or will be ignored. I would stick with the documentation, though, and use D3DFMT_X8R8G8B8, just to be safe.

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