[RESOLVED] Calibrate Corona Sun and Sky Enviro?

[steyin]

I always did what you suggested cjwidd; set sun to .02 intensity and sky to .15, then fiddled with EV.

Artistic integrity aside, I feel that if sun & sky is already set to real world, then you shouldn't be able to change their values; or rather make it idiot proof/clear that one doesn't need to change their settings otherwise.

[cjwidd]

Well it's very comforting knowing their is an equivalency between the two options.

There is a way to calculate the conversion, but I can't quite remember. I think exposure is logarithmic, so an exposure of 3 is 2^3=8(?)

[PROH]

Hi. It should be possible to calibrate HDRs with exposure set to -5,25 (or wathever you find useful), so that they are matching the sun.

Hope it helps

[mancdan]

I've recently switched from Vray so first of all, hello. Funny I came across this thread, I'm wracking my head around the exact same thing at the moment. I've not had chance to test any of this out yet, but here's some thoughts...

So you "calibrated" your HDRIs that all of them would produce similar brightness at 0EV in Corona VFB? Sure, that's convenient to use (if your light source is HDRI only), but that also means that all of them most likely has physically incorrect brightness and your calibration will be worthless if you'll need to combine HDRI with physically plausible light sources. On the other hand, if you only render cars on the backplates, that's not a problem.

On an exterior Arch Viz scene, lets say we want to use a high noon HDRI. To ensure some physical accuracy we go ahead and calibrate it to a 3d virtual sun. Now, I would of thought after doing so our HDRI would then be more or less physically correct, and any other physical lighting (interior lighting eg) would be correctly exposed in our scene.

What am I not getting here? as it sounds from what I've quoted this would not be the case?

[mancdan]

So I guess what I'm asking is, can we use a calibrated HDRI at all(?) and expect a physically correct scene? Physical sun is the only way achieve realism?

[romullus]

On an exterior Arch Viz scene, lets say we want to use a high noon HDRI. To ensure some physical accuracy we go ahead and calibrate it to a 3d virtual sun. Now, I would of thought after doing so our HDRI would then be more or less physically correct, and any other physical lighting (interior lighting eg) would be correctly exposed in our scene.

Correct, your HDRI would have pretty accurate brightness, but i think this is not what topic's starter was aiming for.

[cjwidd]

@Romullus is correct, I was not inquiring about a method for calibrating an HDRI to a virtual sun, but rather the sun itself. Apparently in the case of Corona, the sun is already physically accurate using default values.