force more samples on per object, light, or material basis

[jasonhuang1115]

Hi,

In SP3, I have a render that I am happy with the result with the settings below.

MSR 6, Divide Shading Subdivs enabled,
AA 2,24, threshold 0.005
DMC sampler: Use local subdivs disable, adaptive amount 0.85, adaptive threshold 0.005, adaptive min samples 16

In post, we push color correction pretty hard. As an example, the noise dark area of specular RE becomes very obvious after the color correction treatment.

I can remedy this by raising the aa min to 20 but it's waste for the majority area of the frame.

Is there a way to keep overall sampling of the frame based on SP3 simplified quality control while force more subdivs just for specified objects, lights, or materials?

Thanks!

[vlado]

There is only the "Subdivs multiplier" in the V-Ray Object properties.

A better approach could be to try matching your post-processing results with the color mapping controls in V-Ray (you can always set the mode to "none (don't apply anything)" to keep the output linear, but you can influence V-Ray's sampling in that way. You don't have to do an exact match, just to get as close as possible.

Best regards,
Vlado

[jasonhuang1115]

Thanks Vlado. The "Subdivs multiplier" in the V-Ray Object properties didn't cut it even with a value of 64 (AA min subdiv 2 and MSR at 6). The most noisy RE in my test scene is the specular RE.

It's a single frame in this project, hence affordable to crank up the min AA and get a cleaner specular RE.

[joconnell]

Seems like Vlado is suggesting something that Lele used to do quite a bit on his film renders - he'd render over exposed so that those dark areas you mention (shadow areas before the affect colour mapping only tab) are brighter when seen by the sampler so they don't lie under your noise threshold as much - use the bright and dark multipliers in the colour mapping to try and get the exposure of your render similar to what it looks like after your post colour correction, then switch the mode back to don't apply so the sampler sees your brighter image when it's calculating the quality for the image but doesn't burn in the brightening - you'll have a little bit more quality in the dark areas you had issues with earlier.

Not that I like doing it but on one or two jobs I put in more blatant reflection and spec amounts on some of my materials - it made the beauty far worse but it meant my elements were cleaner as a lot of that job was being look developed in comp anyway.

[jasonhuang1115]

Thanks John! I remember LeLe talked about this technique. It's just the spec RE for a particular car paint color that we pretty much look-deved the color in Nuke based on a general base car paint color. I am curious if the over-exposed render would take longer to finish and I guess as long as it's not taking longer than using Min AA of 20, then it's worth it.

[joconnell]

You could almost do a hdr of it and render a second version at a normal min aa but with brighter values set via the dark and bright multipliers?

[jasonhuang1115]

hmm....will try that... Thanks!