Best method to work with multichannel EXR ? float newbie

[Pixelab]

I'm experimenting with openEXR workflow only recently (I know, I'm a bit late to the party) and I have some questions :

- Does Vray saves 16bit float if I uncheck the EXR/VRST/VRSM 32 bit output? Is 32 bit necessary for traditionnal archviz work or is it overkill?

- I was using the "separate render channels" before, now everything is embedded into the EXR. That's great but I also get the denoise passes I don't need to save (denoise works so well out of the box), and that bloats the EXR. Any way to avoid this ? I'm using VRay raw image file to write the EXR, do I have to revert to the common 3dsmax render output ?

- What is "dot delimited frame number" ?

- Do color mapping affect the EXR ? I don't need Reinhard anymore, but for a proper LWF, if I switch to Linear, do I still need a gamma applied ? Or everything is discarded anyway ? I Previously I was using color mapping only, and left 3DSMAX apply the gamma, but now I'm confused What's the best method ?

- Do you tend to overexpose your renderings ? I was used to render in PNG (integer) and now that float allows unlimited light, I expose 1 or 2 IL higher to clean the shadows better and "re-expose" afterwards in photoshop/ ArionFx. Is this a good workflow ?

Thanks for your help !

[vlado]

If the 32-bit output option is not checked, V-Ray saves 16 bits by default. 16 bits are typically enough for ArchViz work. You might need 32 bits for Z-depth and maybe world position passes if you use those. In V-Ray 3.5 we always save the Z-depth specifically with 32 bits, even if the other channels are 16-bit.

We don't have an option to turn off the denoiser elements right now, but it is on the "to do" list. For the moment we kept them in case you want to denoise using the standalone tool, or the Nuke plugin. You can reduce the number of additional elements by setting the "generate render elements" parameter of the VRayDenoiser render element to "Depending on denoising type". Then it will add only the elements needed for the particular denoising.

If the "dot delimited frame number" option is checked, V-Ray will add a dot before the frame number in the final image file. F.e. if you specify the file as test.exr and "dot delimited frame number" option is enabled, the final image file name will be test.0001.exr etc. With the option disabled, it will be test0001.exr etc.

Color mapping needs to be at the default settings (Reinhard with multiplier/burn at 1.0, gamma 2.2 and mode set to "color mapping only").

Overexposing is as good a workflow as any; however it is likely that simply decreasing the noise threshold will get you the same results anyways.

Best regards,
Vlado

[Pixelab]

Thanks Vlado for the complete explantation.

I realize that I've been using VRay for more than ten years now and every week I'm finding out something I didn't know. Your software has always been a joy to use !

[thanulee]

@pixelfab
I m always curious about overexposing in vray. I have aliasing issues if i overexpose and cause i always render linear cause of post, im not sure how to deal with this. In photoshop with camera raw all is good. But in AE that i use for compositing, i cant seem to retreive the information proper and same time ballance the arion plugin.
I know these are a lot of subjects to tackle at once, but i was wondering, when u say over expose, what is ur brightest vray value in ur scenes (despite having a sun in the image)? Around 2?
thanks a lot

[Pixelab]

@pixelfab
I m always curious about overexposing in vray. I have aliasing issues if i overexpose and cause i always render linear cause of post, im not sure how to deal with this. In photoshop with camera raw all is good. But in AE that i use for compositing, i cant seem to retreive the information proper and same time ballance the arion plugin.
I know these are a lot of subjects to tackle at once, but i was wondering, when u say over expose, what is ur brightest vray value in ur scenes (despite having a sun in the image)? Around 2?
thanks a lot

I have not a lot of experience in this, and cannot say exactly how VRay behave above 1 in floatn for AA. When I say that I overexpose, it's more like I'm not afraid of the previous 255 limit since there is no clamping anymore. I try to expose to have the bright (but not burned) parts of the image around 1, where before I needed a margin and it was more around 0.8/0.9. This helps clearing noise in the dark parts, but as Vlado says, decreasing the noise threshold will get you the same results.

The idea is mostly to take advantage of very bright spots (like a spot in interior, a bright highlight of the sun in a facade, a candle flame, etc.) to generate realistic glow & glares

[thanulee]

Thanks for the reply. Hmmm i guess then values of more than 1.5 in floating are out of the question since its visible burned areas, unless u tonemap ur images something that AE doesnt handle proper. Thanks again mate