Vray Z depth pass problem

[Steve Davy]

Seen this a couple of times but never been able to trace it.

Using render elements and a Z pass, everything is fine until suddenly the Z pass starts outputting random black and white elements that have no relation to depth. I have not yet been able to find a fix for this. Deleting and creating a new render element doesn't solve it.

Has anyone else seen this and know what the cause is?

[EdoAlf]

Are you modifying the min/max range from the pass, or are you leaving it by default? Zdepth depends on scene scale in relation to camera, and most of the times you have to measure and keyframe the nearest/farthest element on your scene on a shot by shot basis, so you can have a good color range for the zdepth to be useful. 

[Steve Davy]

Yes, sorry I wasn't clear about that. It's not that.

I've traced the issue -- it seems to be caused by the "Affect Channels" attr. on refraction. Setting this to All Channels causes the incorrect grayscale value to be returned, or appears to. I'm not sure if this is a bug or a feature, but since comping depth in post using simple Z depth depends on a single grayscale value, this appears to me to be a bug.

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Date: Mon, 9 Feb 2015 05:42:01 -0800
From: eduardo....@gmail.com
To: maya...@googlegroups.com
CC: stevi...@hotmail.com
Subject: [maya_he3d] Re: Vray Z depth pass problem

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[Pierre Jasmin]

In case, (quote is from chaosgroup support)
I know in Vray for 3DSMax there is a similar issue with other channels, the workaround there is to use V-Ray native saver.
"When you set the output EXR file format to be saved from the VFB Separate render channels or Common/save option, 3DS Max native image writer will be used."
..."there is an option to use V-ray Raw image option".  (i.e. use V-Ray to save image instead of passing through 3DSMax).

Pierre

[Steve Davy]

Thanks Pierre. If I'm understanding you correctly, this is just an option in globals that you can just set when saving to multi EXRs? But in Max?

If that's the case, I don't see anything similar in Maya.

Anyway, in this particular case I didn't need the shader in question to have its refraction set to All Channels -- Color only was good enough, but it would be good to know if there a solution in Maya. My workaround previously was to go old school and use another render layer with a different shader.

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Date: Mon, 9 Feb 2015 13:46:16 -0800
From: jas...@revisionfx.com
To: maya...@googlegroups.com
Subject: Re: [maya_he3d] Re: Vray Z depth pass problem

[Pierre Jasmin]

My test license of V-Ray is out:(

don't you see a checkbox to Render  as v-ray raw image file in v-ray framebuffer?
if so, select browse and pick exr as image type

Pierre

[Dillon Bailey]

You could always save your images as vrimg in your vray Framebuffer history folder and then run the vrimg2exr utility included in the installation. VRIMG files are uncompressed 
32-bit images so having them can be helpful and converting them to scan line zip half exes is ideal :] 

Run vrimg2exr --help for options and how to use.