aliasing issue with Maya VRay zdepth pass in NUKE ZDefocus

[schnitt]

Hi there,

Hope someone can help me with the following:
Got some issues with DOF using a zdpeth pass with NUKE’s Zdefocus.
Got a simple scene: two area lights, a few models and a curved background plane, outputting with Vray to a 32-bit EXR scanline zip.

For the zdepth render element I tried the following settings:
Depth Black: 0
Depth White: 220
depth_clamp / filtering disabled

also tried with swiched black and white values, so:
Depth Black: 220
Depth White: 0
depth_clamp / filtering disabled

I tried different Zdefocus math settings, but with all settings I get an aliased DOF. (you can check the screenshot I upload.)
Also tried comping a double resolution version of the zdepth pass (using the Reformat node and trying its different filters) without succes. Results in the same aliasing.

I didn not try to seperate background and my models and then apply blur, because: if I render a zdepth-pass with Arnold it works fine. No aliasing at all. Because with Arnold I have to divide “1/zdepth” I figured that perhaps I’m doing something wrong with the Vray pass. Some sort of math/value issue.

Anyone got a clue here?

screenshots:
vray zdepth pass:http://cdn.imghack.se/images/c46e9753b371723456d376a11415e45a.jpg
arnold zdepth pass:http://cdn.imghack.se/images/9407647927782120c6cd89b6a310de28.jpg
dof with vray:http://cdn.imghack.se/images/28228db2f23f2a4e412b984a3f4842e2.jpg
dof with arnold:http://cdn.imghack.se/images/49236391935b0513eca0024cf270e27c.jpg

[Anonymous]

Thanks to Mister Vlado from the chaosgroup.com forum who solved this.

The difference between the two passes was the “matte’s” for the objects in the scene were about 1 pixel smaller on the vray z-pass. After setting the “Unfiltered fragment method” in the render elements tab to “nearest to camera”; the size difference is neglectable and the zdepth works as supposed to without nasty edges.

[Author]

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