Traditional zdepth option in render globals

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  01 January 2013
Traditional zdepth option in render globals

This option is available in the render globals in the "software render" and in "mental ray renderer":

When using mental ray, is the zdepth images rendered by mental ray or the maya software, the option is a bit confusing because it doesn't become grayed out when switching to the maya software?

When used in composting, the pass is very shallow (very subtle difference between far and close values in luminence).Why is that?

Is that option really effective for creating the zdepth pass>
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  01 January 2013
No, this option is not for use with mental ray. You'll want to use a renderpass, "Camera Depth" or "Camera Depth Remapped" for doing z-depth. It can be tedious to work with at first, I pulled my hair for a long time getting it to work properly! If you need more help I can dig up my old z-depth thread for you, or just look in my "threads started" link in my profile.
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  01 January 2013
I gave those a try with no success.
But I least I know now, this is the right way.
thanks.
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  01 January 2013
Here is a link to my prior struggles with z-depth in mental ray. One key factor which I may not have mentioned was having a piece of background geometry, like a plane with an image mapped to it, even if it wasn't set to primary visibility at rendertime. You need that "far bound" calculation to make z-depth work, at least through cutout opacity.

I'd love to help you get past this issue, can you share any images or examples of your results?
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  02 February 2013
Originally Posted by InfernalDarkness: I'd love to help you get past this issue, can you share any images or examples of your results?


not yet but I will soon.

*Should the Zdepth be rendered in a linear space for a correct linear workflow? or is it irrelevant here?
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  02 February 2013
zDepth should be rendered to 16Bit half or 32Bit float depth and those color depths are usually not affected by gamma.
A part from that, being it measures, you just want raw data. I guess that when you use the passes mental ray take care of that for you.
 
  02 February 2013
Indeed, I've been rendering my z-depth pass to 32-bit .tiff files, it's a bit overkill but seems to work really well. Certainly good enough for my still shots (I don't do a lot of animation), but from what I've seen they'd work great in Nuke as well. .exr files might be better, but I'm still on Photoshop CS4 and there's little native integration. So .tiff files work great, for now!

That is to say, z-depth doesn't care about gamma correction or colorspace. It's simply returning the distance from the camera to a polygon/pixel as data, which is converted to an image gradient. Color correction and gamma don't affect this data; it's already present in the raytracing math of your render, the depth pass is just spitting that out as a separate image with little if any rendering overhead.
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  02 February 2013
Ok, that's clear, I forgot that MR passes don't take the camera lense shader into account (apart from the beauty pass).
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  02 February 2013
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