vray aerial perspective altering multimatte saturation

[vance3d]

I've been using the aerial perspective and I noticed it seems to be writing to the multimatte as well thereby altering the saturation of the rgb.

thanks,

V Miller

[matanov]

You are right, thanks for the pointer !

[matanov]

Apparently, after a talk with our developers, this is the way it should work.

[joconnell]

Would you have to do something like divide your multimatte passes by the alpha of an aerial perspective element then to restore their full strength?

It's often a bit of a tricky one - how do you retain flexibility with semi transparent objects like fog or haze when compositing. In some ways I'd love to have an option for aerial perspective and fog that you can choose to have it as an element only - the solid parts of the render don't have any of their elements affected by the atmosphere and we get our fog as a separate layer. It wouldn't be as correct but might be handier for comping after.

[Art48]

Having masks affected by that effect is nonsense to me. If it is intended, it's not good in my opinion. I need full strength normal masks. If I wanna do fancy stuff with it then this is post and shouldn't be already done in the rendering, except as togglable option.

[Seraph135]

+1

I really wish multimattes were not affected. Can someone explain why it is the intended behavior currently? What is the benefit of this?

[joconnell]

Like in some ways it makes sense since the pixels are made up of a percentage of the solid object and a percentage of the haze in front of it. In terms of what you'd do with the mattes and passes after though it's not as helpful.

[Morne]

I prefer my multimattes to be clean

[vlado]

I prefer my multimattes to be clean

Why is that? You will get the same "issue" if there is a semi-transparent object in front of the multimatte; it is also because of this behavior that the mattes work correctly if there are opacity-mapped objects in front of them - you don't have any objections to that?

Best regards,
Vlado

[Seraph135]

I see your point there Vlado. I'm sure this is a potential problem for a number of users out there. Semi-transparent opacity maps are fairly rare in my workflow these days, but I'm sure this is not the case for everyone. I'm pretty much always rebuilding the beauty from AOV's, and environment fog is used in almost every scene at this point. I'm doing all my tweaks using the multimattes on specific AOV's prior to layering on the environment fog. So having the multimattes affected by the fog is not helping. Is it out of the realm of possibility to give us a checkbox to enable/disable the fogs affect on multimattes?

Tim J

[vlado]

Is it out of the realm of possibility to give us a checkbox to enable/disable the fogs affect on multimattes?

Unfortunately it is; it is very hard for me to make an effect like that work on some arbitrary render elements but not others. If this behavior is not wanted, it would be best to render the aerial perspective on a separate pass.

Best regards,
Vlado

[Seraph135]

...it would be best to render the aerial perspective on a separate pass.

The problem is if you render the fog separate then it won't show up in reflective objects in the main beauty render. So instead I end up rendering my multimattes separate from the beauty render.

Tim J

[vlado]

That one is easy, we are adding an option to not affect camera rays (but still appear in reflections and refractions)

Best regards,
Vlado

[joconnell]

We really need to get a thanks function on the forum to replace redundant posts like this one

[Dariusz Makowski (Dadal)]

Same issue. Need clean multimattes or a way to hide Aerial from camera rays but still show up in atmosphere - is that possible?

Regards
Dariusz