Re: Problems with Alpha blending

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Sharon Clay (src++at++rose.asd.sgi.com)
Mon, 25 Nov 1996 12:08:34 -0800

+>---- On Nov 25, 6:21pm, Angus Dorbie wrote:
> Subject: Re: Problems with Alpha blending
->
->An old favourite.
->
->This is multisample transparency working on an antialiased visual vs
->blended transparency on a non antialiased visual.

This sounds like a good guess.

->
->On RE2 you can improve things by sorting geosets and culling alpha pixels.
->You could even try a lower resolution framebuffer to give a bigger pixel
->depth.
->
->On iR you should be able to select a different visual to get multisample
->transparency. The secret with small pixel depth is to request a 15 bit
->zbuffer. I think the safe strategy is to ask for a 1 bit Z which delivers
->the best available given other attributes.

FYI, on iR with 1 RM6 at 1280x1024 you should have medium pixel depth and
you can get 23 bits of Z with 8 multisamples and 1 bit of stencil.
However, I strongly recommend that 15 bits of Z be tried becuase of
its faster fill rate - be sure you really need what you are paying for.
If you request 1 bit of Z you are more likely to to get a success, but
glXChooseVisual (what we use internally) will maximize the result so may give
you more than you need or want to pay for.

If there is any doubt as to the contents of the visual:
1) setenv PFNFYLEVEL 5 - Performer will print out the multisample & Z config
        when it starts up
2) the following on a running program will show you what you got:
        % xwininfo -tree (click mouse in performer window to get hierarchy)
        % xwininfo -id 0xid (give id of main drawing window - not overlay
                                or parent container)
        look for visual id
        % glxinfo - look at attributs of visual id

src.

-- 
-----{-----{---++at++   -----{----{---++at++   -----{----{---++at++   -----{----{---++at++
Sharon Rose Clay (Fischler) - Silicon Graphics, Advanced Systems Dev.
src++at++sgi.com  (415) 933 - 1002  FAX: (415) 965 - 2658  MS 8U-590
-----{-----{---++at++   -----{----{---++at++   -----{----{---++at++   -----{----{---++at++
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