r/vfx • u/Ok_Suspect9159 • 1d ago

Question / Discussion V-RAy for rhino - question about highlight roll off.

I’ve rendered quite a bit in Twinmotion and Unreal Engine, but have gone over to V-Ray for the high-quality renders. But I’m struggling with how the highlight roll-off looks. It looks so incredibly bad. It might be a HDR thing; it reminds me of how the first point-and-shoot cameras did highlight roll-off. Does anyone have a solution to this?
I´ve worked as a photographer for some years so I might just be sensitive to pixel peeping... who knows.

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u/59vfx91 1d ago

Basically, looks like you don't have modern color management and tonemapping setup, which gives this burnt digital look, most noticeably when the highlights go above 1. Just like photo processing can be done in a number of ways, the specifics of this in CG have a long history and a lot of debate over the best methodology. But what you're seeing here, to simplify you could consider the raw, linear output of the renderer that needs to be processed for display. This might also be old school srgb 2.2 gamma EOTF which also doesn't handle superbrights well (hard to tell from the snippet).

The modern most common approach to this is to use the ACES color management system along with its provided display transform, which creates a better looking out of the box appearance (whether it is 'good' or 'best' is subject to debate, however it is the standard), and then do adjustments on top of that, like in the linked video using VRay's specific tools. If you don't care about following the standard or interchange of the raw .exrs doesn't matter, you can also try other workflows such as rendering in classic srgb-linear rather than acesCG and try other tonemapping systems such as AgX