On z pass precision

Started by uuderzo, July 22, 2020, 11:29:04 am

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I'm trying to test the z pass (or Depth render element) and if i try to output as TIFF file i get a really poor result (also if i output 16 bit tiff).
Should z pass be saved in EXR format at full precision?
I'm asking that because i'd like to re-input the z pass into TG like if it were an heightfield, but TG doesn't read EXRs.

I tried to tweak the near and far clipping plane in the render node but looks like it is ininfluent.



Why doesn't TG read EXRs? I use EXRs with the image map reader.


I'm not sure what you're trying to do, but seems it will be a real pain to update if anything changes. EXRs do load correctly, make sure you check Data is linear in the colour tab of the image map shader. Full float is the most accurate.

That said, will a distance shader do the same thing?


Definitely the Z depth pass should be full precision (32bit) - all the Render elements under "Data" (Motion Vector, Position, Normal etc) should also be 32bit.

Exr is nowadays the standard for render elements and Tiff can sometimes be problematic. Exr is a pretty robust format.

The only caveat is that 32bit is overkill for the RGB and Lighting Render Elements, which can safely be 16bit, and there's no facility to change the bit depth per render element currently.


@WAS yep! I simply didn't try to read an EXR. It works... well i suppose it works.

Looks like the ZPass outputs a very low precision EXR image, i mean... i want to use it as an heightmap but looks almost impossible to reproduce the original surface, looks like very blocky. Sure it's me but don't understand where i'm failing.

I'm not using depth shader because it looks like it's working only on landscape, and it ignores object populations. I want a depth map of the entire scene, with objects, so i can process it further by re-routing it into TG again.


james adamson

What about outputting the scene as a model with all the objects and the camera and generating the depth pass at 32 bit in another app like AE or Nuke?

james adamson

Or Fusion? I think that has those capabilities although I have not used it.