Vray and AA of black

[Morbid Angel]

I always wondered why vray has hard time antialiasing black empty space. When I set settings high, for animation the black takes very long. Im wondering if its possible to include some kind of algorythim that would detect that if there is absolutly nothing in the bucket that it would move to next bucket without sampling it in any way.

[vlado]

Which AA method are you using? Is the black part also with uniform alpha channel?

Best regards,
Vlado

[Morbid Angel]

Ok, I got some time to do this so here is what I got:
Same scene is rendred in vray and brazil. Settings for vray are:
Adaptive QMC 1/4 with standart qmc sampler 0.005 noise and 1.0 global multiplier.
Gi is quasi monte carlo for both bounce
Brazil is preset 3: aa at 0/2 Gi is quasi monte carlo for both bounce

The reason this scene is positioned so is to show that 70% of the scene is black space.
Vray rendered at 7 sec




brazil at 5 sec





Now I have tunred on the DOF with Apature of 5 on given distance it produces no visible blur however its there

Vray rendered at 20 sec



Brazil at 13 sec



The conclusion is: vray and brazil both rendred the object space at approximatly the same time. However the black space vray was rendering for the extra 7 seconds, while brazil flew right thru it.
This issue has concerned me for a long time. While this is simple scene one can argue that the settings can be adjusted, I can only say this:
I was rendering a shot where it had a helicopter in it, from 5 min per frame 1.6 minutes was for helicopter and 3.4 minutes for black space.
Hope that explains my concern.

[Morbid Angel]

Also, same goes to background image. For some reason vray tries to resample the image which takes long time, and is unnesesserry.

[Morbid Angel]

any coments?

[Sushidelic]

My comment:
I absolutely second this one! It was driving me insane when rendering small elements on 2k res with high antialiasing and Motion Blur... Nearly 3/4 of the time for just black BG with black alpha channel - i always had to use render region to shorten rendering times i cases where it was possible. It is true that with brazil buckets are always flying over empty space regardless of the AA quality.
Regards, Michael

EDIT:

Check out this max5 file and you'll see what i mean

http://www.sushidelic.com/tmp/empty.rar

[Morbid Angel]

totally agree thats why I also use render region which is not the way to go

[Morbid Angel]

Vlado, can you coment on this?

[cybling]

Yes i have to agree with you on this one - i noticed this quite a lot when making my short film...i thought it was really strange.

[percydaman]

you've got my vote...

[s7en]

Yep, this has bugged me for a long time too, especially when doing largescale work for print - some A2 sized print work with a lot of empty space would take about 45 minutes just to render areas of blank, white background.

Render region helps, but when you're up against a deadline having to render 60 print resolution images, this is the sort of thing that makes you drop vray and use another renderer