Vray Overcast Sky and Curvature of Earth.

[Sketchrender]

Hi

I have a two questions.

 

Q1. I would like to produce an image with practically no shadows, and an over cast sky with out using a HDRI.

 

I am using Vray 2.40, I have set the sun setting to Overcast and shadow multiplier to 12+ and I am not entirely happy with the results.

 

Q2. On Very large scale models, and very distant views, i.e. a few Kilometres away, how do you calculate for the curvature of the earth and the Z depth, for accuracy.

 

 

Any advise would be grateful.

 

Thank you

 

Phil

[RyderSK]

I know of only single software that calculates curvature of earth, and that is Terragen. I highly doubt without PostProduction trick anything is doable.

 

The default Preetham Sky model can't simulate anything outside of nice blue sky properly. The CIE has "Overcast" which you've set correctly, but you no longer need Sun at this point (or use extremely small intensity 0.01-0.05).

The only problem with this is, that when Sun doesn't contribute most samples, the Environment slot doesn't by default do the job much, so I would advise to use the VraySky inside VrayDomeLight (even though it can sound absurd, the sampling from DomeLight would be quite necessary) or with portal lights for interior (in both cases, the light source will do the sampling, which lacks with Environment slot).

 

With pure overcast, I see little reason why not to go with HDRi/Domelight. Neither Sky model in Vray is very advanced (Maxwell and Indigo on other hand have quite high-level sky models and sample them directly). With zero shadow, you can even use .jpeg in Domelight, which will sample very fast. Downside would be lack of good reflections, because even if the overcast sky doesn't feature enough dynamic range to produce visible direct shadows, it makes big difference in reflections (highly visible in glass panels).

[Ricardo Eloy]

Juraj, you don't sound absurd at all. Using the VRaySky (or an HDRI map, for that matter) inside a DomeLight is the way to go.

Philip, AFAIK Max does not calculate the Earth's curvature. In fact, one would only notice it after a few miles from the camera, and fog would probably hide the effect, anyway. Following Juraj's advice, I'd try to solve this in comp.