Z-Depth/Alpha with refractive materials

[Cruz]

I've rendering glossy refractions recently and noticed the Z-depth pass does not include any refractive information.

I'm not sure if this is true, but I'm not getting any correct Alpha either with glossy refraction.

I found a thread from February on the boards where someone said,
the alpha will only work when refraction glossyness is set to 1 hence refraction without gloss.

I would really like to do a sexy frischluft DOF to my images but without taking glossy refractions into consideration this wont work correctly.
If the alpha was working I could just multiply it on top of the z-depth

Here are some of my incredibly stunning (ha ha) test images rendered with 2 VRay Arealights and a Lightdome

RGB
ALPHA
Z DEPTH
MULTIMATTE


Whats the verdict on this and/or are there any workarounds?

[joconnell]

That's true, the problem is that z depth can only hold a single value per pixel, so does it record a value for the reflections on the surface of your sphere on the left, or does it record a depth value for the objects being refracted through it? Does it do a glossy sampling of the depth values to be correct also?

Unfortunately zdepth is a fairly simplistic fake, perhaps something better will come along with exr 2.0 and deep image files but you'll need to have a new version of frishluft that supports multiple planes of information -I'd bet on nuke having all of that before frischluft.

[Cruz]

alteast the alpha SHOULD be able to do blurry refractions

[joconnell]

To be honest if the object is refracting something which it is in this case, you'd find it hard to pull out the correct pixel values and attempt to comp something behind it that looks correct.