I was just reading about some newer research into defining more accurate skylight models, including a critical review of the Preetham model.
One of the newer skylight models (2012) by Lukáš Hošek and Alexander Wilkie was added into LuxRender.
Would something like this be difficult to implement in V-Ray? Are there other improved skylight models which would be worth considering for V-Ray
I would be curious to hear what others think. Please see the linked references below.
Thanks,
Tim
+1 for this! The current models has some weaknesses for me, and most of the time I am blending together different HDR’s to get my desired sky and illumination.
In lighting cars for example, we often need a very nice horizon shortly before sunset. That is the biggest problem with Preetham, in these situations it looks just wrong. The horizon is way to uniform, and the falloff from orange to blue looks different in reality. The second link from tarn describes that problem very well.
It’s not particularly difficult and it’s somewhere on the “to do” list. But I suspect that using a real HDR image is always going to be more realistic. I’m not sure if something like that can be coded in OSL - you can give it a try if you are interested.
Best regards,
Vlado
Any of these include dusk, or is that something that can be added? Even if it was a simple fade Dusk - Wikipedia
half our images are at dusk, and half our animation work is timelapses. it would get used so much.
+1 to this. I get that HDRIs look better but sometimes they’re just not flexible enough.
Some sampling control within the vraysky would be great too 
would be a good start for day - dusk timelapses when combined with a cloud map
+1 like the sound of this
+1 on this also. Would really love it and use it!
Can you elaborate on this? What is it about them that you dislike? (I’m curious is all, we’re gearing up to start selling ours and we interested in what trips people up.)
i still found it kinda hard to remove haze on the horizon like we get nice clear days right to the horizon in the caribbean
The two main problems that come to mind is a good looking HDRI might not have the sun in precisely the correct spot. Sometimes one needs to position it perfectly for highlights or particular shadow shapes.
The other thing is aside from adjusting an HDRIs gamma or editing it photoshop, it’s pretty much as-is. One can’t adjust sky-saturation as quickly and easily as the sun/sky system, or increase or lower the sun’s power independently of the sky for eg.
need to be able to adjust the sun angle mainly
Yes, hdri domes are great when they correspond to the look you’re after. But if it’s not the case, there is not much you can do. Some color correction, a reasonable change in vertical rotation to bring the sun up or down, maybe brighten the sun in photoshop and that’s all.
But hey, these are only photographs after all -with many exposures within, sure- but still just photographs. If you need more flexibility you should explore other methods.
Using a vray sun+sky in conjunction with mapped couds would give much more freedom to position the sun directly within 3ds max.
Another option is to render your own HDR domes. But then you cannot make adjustements directly inside 3ds max. I recently started experimenting this method with terragen and it’s giving good preliminary results.
I cannot post current projects, but here is a quick and dirty example of an hdri dome rendered in terragen with standard settings, only changing the sun angle decreasing from 45 to 0 degrees :
BTW : does eon ozone do the same thing directly in 3ds max ? Never had the time to try it.
If the HDRI’s came with a nice mask for ground vs. sky, would that be something good to have to solve this problem?
That looks excellent. V-ray having something like that inside 3ds Max would be great.
That would imply developing a full fledged procedural sky system generator. If Planetside Software could develop a subset of terragen with only the sky system and make a plugin from that it could be great. That’s what ozone already does but it doesn’t seem to be much used.
Yeah, I should have phrased it as “having something like that inside 3ds Max that V-ray can use”.
I will have a look into Ozone.
