hdri exr saved from photoshop, weird behavior

[seandunderdale]

Hi,

If I save an hdri with EXR-IO plugin, and RLE format, I get correct results in Maya. If I save an hdri using Photoshops own exr save options, and select RLE, I get very very wrong results.

Pale shadow is photoshop exr, "correct" shadow is EXR-IO saved exr. Same RLE format, same scene....I have a car, on a floor with a matte shadow setup. HDRI is a finite dome. CPU render.

To be honest, Id been dealing with this pale shadow issue for ages, since I always used photoshop to save exrs, not exr-io. I always had to drop an area light in to fix it.

V-Ray 6 for Maya, update 2

(v6.20.00 from Feb 11 2024)
Maya 2024.2

[chuckie7413]

Seems like the HDR is maybe getting clipped (maybe not to 1 but maybe to a lower value) in the brightest part (sun) on the photoshop export?
Have you tried opening the HDRs in nuke and comparing the values to see if there is a difference in the output?

If you see no difference then that would be odd and maybe something in the file headers or something that then causes some issues for vray to read it. Maybe try different output or .hdr format?

[seandunderdale]

Values look identical in photoshop 32bit eye dropper, and in Nuke.

hdr format also fixes the issue...but I cant load in an hdr format file at 16k without the viewport freezing....so it looks like 16k exr-io is the way forward until I hear otherwise.

[chuckie7413]

Hmm then if identical then something with how the file is written that vray struggles to pickup so maybe worth a support ticket to them about that.
But maybe you can just use ZIP compression instead. Or i assume then you chose RLE because it was the only one not freezing your viewport?

[seandunderdale]

Ive been testing different formats...I avoided exr-io in the past as I seemed to always get outputs that didnt work for me...produced a black render in Vray...but I wanted to test it out again and see if there were speed gains over hdr format...and also see what max res I could get with each instance. Turns out in Maya 2024, I cant use 16k+ .hdr format files as they freeze my viewport, even with textures turned off.

photoshop exr saved as RLE format was always my go to format, but comparing to the exr-io it seems Ive been using something that is clearly broken...though I cant say if its a recent thing, or if Ive just always been using a format that has been clipping my direct light. Attached are two more shots on a white floor...the brighter one is saved with exr-io, the darker one is the same hdri file saved via photoshop exr.

Using EXR-IO I have switched from ZIP format to DWAA as visually there seems to be no different in my render, and the hdri file is 70MB instead of 1.2GB.

[chuckie7413]

I meant try using ZIP from photoshop.
But yeah you can see there is a clear difference in something between the exr-io and ps output that uses the same compression. If saving as other formats from PS (ie .hdr) creates the same output as the RLE exr-io export then you know there is something wrong with the photoshop RLE output. (or something wrong with how vray handles the file. you could see if arnold reacts the same with the same files to see if it is a vray thing or a file thing).

Exr-Io warn that DWAA may cause data loss. Although not sure where in regards to a single layered exr image. Maybe in a more complex exr layered file.
https://www.exr-io.com/openexr-data-compression/

Best,

Richard

[seandunderdale]

I saw docs also for DWAA on exr-io site, they say that there should be no visible difference in the image. I will need to do a high res comparison, but as long as the results in my renders are the same, I don't mind it being lossy.

In terms of the open-exr format from photoshop, there isnt a ZIP option...options available at output are Zlib, Wavelet, RLE, PXR24, or none...it feels like photoshop havnt really looked at their exr tools in a long time.