AA Problem

[jonnybefree]

Hi all,
its really strange, but i can't get rid of the AA Problem here:



there are allways these aa steps there, i cant get an clean aplha.

i'ma using:
adaptive qmc:1/4 (try'd even higher) / and try'd also adaptive subd.
Area 1.5 (try'd even all other without succes)

any tips?

best regards
jonas

[jonnybefree]

??
nobody there?

[instinct]

Depending on the target (broadcast ? print?) i'd say go for cubic AA filtering blurs a bit but reduces jagginess.

Thorsten

[jonnybefree]

hi instinct,
for this time its a broadcast thing, i can fix it simple by rendering before white, but isn't it possible to get a clean alpha?
I've try'd even the cubic, its all the same problem there.

[Joost Ink]

what if you do adaptive 0/3 check outline, threshold 0.05.
with qmc noise treshol at 0.003
that works most of the time.

[Candelero]

what if you do adaptive 0/3 check outline, threshold 0.05.

Or even less than 0.05.

Best regards,
nikki Candelero

[jonnybefree]

no changes there:



adaptive 0/3, outline checked
threshold down to 0.01
qmc noise threshold 0,001

but for clear:
i saved as png, 48 bit, and post it in PS or AE

[jonnybefree]

hmm, am i doing something wrong, or its a stupid question?
all i want to have is a clear alpha

[dlparisi]

How are you lighting this scene? Is the background white (255,255,255) or something above (HDRI?) You've probably seen the problems with jaggies on overexposed items-maybe it's related to this?

[jonnybefree]

no this is only a testscene,
no lights, Vray LightMtl, renderd before black, saved as 48 bit .png, and composed in PS.

[RErender]

the objects are premultiplied on the black background so the black is mixed in the semi transparent pixels at the edges, solutions are to save whithout a premultiplied alpha or in PS go to layer/matting/remove black matte

[jonnybefree]

hi rerender,
yes when i'am removing the black matte in PS or AE, i think hes cutting the black pixels, so it doesn't fit perfectly anymore.

and how can i save a strait alpha out of max?

[vlado]

hi rerender,
yes when i'am removing the black matte in PS or AE, i think hes cutting the black pixels, so it doesn't fit perfectly anymore.

and how can i save a strait alpha out of max?

There must be a "premultiplied alpha" option that you need to (un)check somewhere... either when saving the image, or when loading it in another program. TGA's have such an option, not sure about PNG files.

Best regards,
Vlado

[jonnybefree]

ok, you're right, the premultiplied alpha gives a clean alpha
but look at these steps:



i've even tried the highest aa settings, dont want to blur it too much, just a nice clean corner.

[vlado]

ok, you're right, the premultiplied alpha gives a clean alpha
but look at these steps:



i've even tried the highest aa settings, dont want to blur it too much, just a nice clean corner.

This is expected in the RGB channel with non-premultiplied alpha, yes. The idea is that the RGB channel combined with the alpha will give you the nice edges. In that case, the RGB channel itself will look jaggy, but the alpha will smooth this out later on in your compositing application. The whole problem originally appeared because the RGB channel was smooth - once you smooth that again with the alpha, you get the black edges.

Best regards,
Vlado