Hi, I got some glass material with colored fog. “Color + Alpha” is on under refraction “affect shadows”. I’m using “Vray raw image file” to save my renderings on farm.
I can’t find a way to save the resulting colored alpha as a render element. Is the only way to turn on “separate render channels”?
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If you want to extract all of your render channels that are part of the VRIMG, you can do so by opening the VRIMG in the VFB and save as seperate render channels. (Save all image channels to seperate files).
Or you can view your alpha channel and save only that channel (save current channel), or you can copy paste when viewing that channel (or use the image > copy to clipboard) and paste it in photoshop or whatever you use.
There’s also a tool that can convert VRIMGs to EXR (vrimg to openexr converter in vraytools), there you can also specify which channel to save to openEXR or all channels seperately.
If you try to render a colored glass object with “Color + Alpha” on Vray vfb will show you a colored alpha. That’s because in order to keep the same aspect you have to export that channel, invert it, multiply it on plate and then screen the beauty on top (without alpha).
Otherwise trying to comp it with standard alpha will look like crap.
You can also see this when saving using separate render channels with “save alpha” ticked: it will save the colored alpha as a separate file.
My original question is about not saving it as separate file BUT having it as a render element, thus allowing to embed it all in an exr instead of forcing me to save separate render channels.
You are right, sorry, I tested this before answering but didn’t notice that there was a color difference (didn’t have a strong enough color in the fog). And to this day didn’t think about the fact that when using the alpha for instance in photoshop will indeed not hold the color information when used as a mask. Thanks for pointing that out, can’t believe I missed this.
As for an answer to your question, it depends on which package you use but you can use the ProEXR plugin for Photoshop, After Effects, Premiere or Nuke: https://www.fnord.com/
You can open VRIMGs with it and the alpha channel still holds the color information, just tested this.
Thanks for testing! Weirdly enough using .exr won’t do - I’ll try with vrimg then, thanks!
Still, I’d love it to be a render element… would simplify things.
Yeah I tried with EXR but it didn’t work, seems it only works with VRIMG. If you want, you can ask for the developers to consider this idea: https://chaosvray.ideas.aha.io/ideas
This is an old topic. Long story short, the.EXR format writes Alpha data as a mono channel (not an RGB channel) by design. We have an option to write it as RGB in the VRayOptionsRE element, but it affects only deep images. As @Vizioen already suggested, one workaround is to use .vrimg; another is to output both a Raw image and Separate Render Channels (to use the Alpha separately).
Yeah, I’m using the second. But if the colored alpha could be saved as render element (not alpha!, just like any vrayextratex) would solve the problem, no?
Right now I have all my render elements embedded AND the ones saved separatedly only to have that colored alpha as a map.
Hi Aleksandar, couldn’t find this info in the docs, if it’s there. Otherwise would be handy to put it in there for future reference.
The thing is that no software supports such alpha channels (Nuke included). I asked @vlado about it, and he told me there’s no standard way of doing it. Even if we add such an element, it would just automate what we already have now.
You can directly save the Alpha channel from the VFB, too.
Yes.
After discussing this again, we’ve logged an improvement request (internal tracker ID: VMAX-14912) for a separate VRayAlpha render element that holds RGB info.
that’s amazing, thank you!
Yes, please. A separate colored anlpha element in non-deep EXRs. Then the standard mono data can continue to be saved in the Alpha channel. This way we can use the colored data however we want in Nuke, and everything else still works as usual.
(And most importantly we don’t have to use deep when we otherwise don’t need it, or save two copies of all our data to get one element. )
Thanks.