DeepImage EXR - alpha value slightly below 1.0

[ultrasonic]

Hi Guys,

we just have an issue here with deepimages, that show alpha values in some places where the non-deep EXR shows exatly 1.0. In the deep files the alpha is around 0.99951. See screenshot attached...the black areas are actually 0.9995 an not 0

LEFT = non-deep RIGHT=deep-EXR

Do you have an explanation for that, or is there a simple setting that we have overlooked?

thx in advance
Oliver

[vlado]

Can you get me the Maya scene that produced the file?

It might be a bug.

Best regards,
Vlado

[TKman]

Hello,

fortunately there are other people out there with this issue
I just wanted to update this thread, as we just ran into that Alpha thing. We have been testing with Vray 3.0 as well as 2 and both show this behavior. The Alpha values show this slight noise-like variations, resulting in quite some issues if used inside of Nuke.
We also do have an issue that might be related to this one. -> Having hidden geometry in front of an object will result in outlines being in the alpha and ID passes. Looks actually quite similar to the pictures posted by ultrasonic last year.
thanks a lot!

Thomas

[vlado]

This is somewhat better for the nightly builds, but if you are saving to 16-bit deep files it might be normal - the values lose some precision and may not sum up to 1.0

Best regards,
Vlado

[TKman]

Hi Vlado,

we did some testing using a 32 bit output this time. Unfortunately, this noise pattern is persisting. It most definitely seems to be realted to hidden Geometry (including light planes ). Rendering a simple object without anything in front of it works fine.
tests included VRay 3 and 2 with Maya 2014

thanks,

Thomas

[vlado]

Then it's best to send us a scene that reproduces this.

Best regards,
Vlado