Vray Sky - Lots of questions.

[Deflaminis]

Anyone know if it is possible to change the horizon height with Vray sky? I find it to be too foggy compared to my reference, and even after messing with ozone and other various effects, it often times just seems too.... gray near the horizon. I'm sure this is realistic and physically accurate, but I'm not able to match the reference when using the same camera settings in vray as in real life. When I adjust the camera exposure to make the sky blue, it seems to have a bad effect on the sunlight. I can't see to get these two elements to work together correctly, other than rotating my scene so it looks upwards and I see the bluer parts of the sky. I am approaching it like I would normal photography, but no matter what I do the sky is just too gray/washed out in terms of saturation and color when I get the camera to expose the sun properly. (Sun is at default intensity.)

How do you guys deal with this? I really don't want to rotate my whole scene just to get the sky blue, and the client is saying no post work can happen so it all has to happen in max. This has me wondering what is the best way to handle this.

Additionally, in mental ray you can map a sky image to the haze map to get a sort of sun through the clouds look. IF I am locked out of a post workflow and have to do it all in max, is there an easy (or even hard) way to accomplish this in vray?

In the past I'd just do it in post but again I don't have that option here and I'm unsure the best way to handle this.

Thank you very much,
AJ

[plastic_]

the client is saying no post work can happen so it all has to happen in max.

How this?? Do you deliver a .max file?

I'm using sky/sun, for lighting/reflections, but always replace the sky background with photoshop.

[Deflaminis]

Client wants blue sky, no background, from max. I've mentioned it would be cheaper, faster, and better to have a bit of comp but the client is king. I get where they are coming from however, they don't have a dedicated max person on staff so they just want a quick 1 button solution to the problems. I'm nothing if not flexible, so no problem.

Right now my only solution is to rotate the environment, which makes me feel like a hack.

I deliver a max file, which the client uses to render. (They know nothing of rendering (which is fine), so they want to just position the camera anywhere they want in the scene and hit render and get a decent render in little time, and then send that straight to w/e programmer plugs it into their end of the project. Never thought I'd use photon mapping but I was wrong. It's actually kind of fun. :P)

As I type this, I wonder if I can just raise the environment 5000 feet off the ground.

Edit: clarity.

[plastic_]

You can separate the env. background from the Vray env. slots.
Or you can use the same Vray Sky map for the background, but route it through a Color Correction map, for background only. That way you can saturate/desaturate the background sky.

But the whole concept of client moving the camera around is flawed, IMO.
As soon as you move the camera you also have to tweak lighting/sun position, for optimal results.
The sky color depends a lot on the sun position relative to the camera, as you will have noticed. Maybe you're better off with a static background, for example a gradient?
And a more stable/conventional lighting approach, like omni lights.

[Deflaminis]

Raising 5000 feet didn't change anything, but using a VrayCompTex with the sky in one channel and a very light blue in channel B on multiply seems to have solved the problem well enough for this case.

I took it a step further and tried an HDRI in the place of the light blue VrayColor and actually have a pretty nice blend of the vraysky and the hdri sky that looks quite pleasing and has enhanced my darks a bit which I am not at all upset about. So I am happy there and seem to have solved the issue without increasing render times much.

I would love for the vraysun to see the hdri sky and cast shadows accordingly, but am unsure how to do that. Is this doable? I didn't have a lot of luck with the procedural atmospheric gizmo noise clouds and photon mapping. Was hoping there was a pseudo haze trick that's doable in this case.

Thanks to anyone who can shed some light on this one.

[Deflaminis]

But the whole concept of client moving the camera around is flawed, IMO.
As soon as you move the camera you also have to tweak lighting/sun position, for optimal results.

I understand and have explained this. I taught them how to change exposure and it's working well so far. I'd rather not make waves fighting an unwinnable battle.

The kinks have been worked out and the renders look good from whatever angle, it's just the sky that is the problem. Redoing all this work with omnis isn't really an option here. I actually inherited the scene from another artist who couldn't get it all working so they are already pretty happy that I got it this far and the renders don't look bad at all. They just don't match the references in terms of sky color. The camera will never look up higher than say 10 degrees and the sun is high in the sky so it's pretty even color as the camera rotates 360 degrees.

Ideally they want the same look as mental rays map in a haze channel trick, so a gradient doesn't quite cut the mustard. I think I have it worked out using a vray comp tex and the sky + hdri. Looking pretty close here, just no shadows from the hdri. Not sure how to pipe in a gobo into the sun but that would also work. Maybe I'll just use a directional and call it good.

[vlado]

I would love for the vraysun to see the hdri sky and cast shadows accordingly, but am unsure how to do that. Is this doable? I didn't have a lot of luck with the procedural atmospheric gizmo noise clouds and photon mapping. Was hoping there was a pseudo haze trick that's doable in this case.

You can use a VRayPlane mapped with some procedural noise that is only visible for shadows (you can use VRayOverrideMtl material for this). Put it high enough above the rest of the scene and you should be able to get nice cloud shadows.

Best regards,
Vlado

[greysheep5]

You can use a VRayPlane mapped with some procedural noise that is only visible for shadows (you can use VRayOverrideMtl material for this). Put it high enough above the rest of the scene and you should be able to get nice cloud shadows.

Best regards,
Vlado

actually quite a nice idea to use a vray plane with a noisemap as procedural cloud shadows in the atmosphere, wouldn´t have thought about that, thanks!

[3DMK]

Have you Tried the CLEAR mode of the Sky instead of PreethamETal.

The clear mode for Vray sky gives much bluer skys, with less haze.

[Deflaminis]

This worked wonderfully. Thank you Vlado.

[Deflaminis]

Yes I am using clear mode currently, which allows me to adjust the indirect illumination of the sky which is nice.