God Rays.. yes that old chestnut

[stelees]

Hey there,

I am really REALLY struggling to get god rays in a forest scene happening.

I have done all the things I have read.. I have a vray sun.. set to about 1 - 2 intensity, size is about 5. Fog distance is about 30 metres and the height around 20 metres. Scatter bounces is 1, subdivs is 8.

I have the sun at around a 45 degree angle.. a number of trees in the way to filter the sun to the ground but nothing... if I turn up the intensity it washes out the scene.

Does anyone have a sample scene I could tear apart to see where my dumbness is residing with this one? 3ds Max - latest vray next. The attached shot should produce something... there is a plane with a lattice modifier attached to it so there should be some sort of filtering of the light..

Just nothing. AND when you look at it the scene is so brown and just blergh there is no way this lighting is even a hint of what it should be.. i.e.a typical nice and crisp view in a forest with whitish / light grey god rays blasting through. I see it all the time when I am out 4wding.. it has to be achievable here.

Thank you heaps

S.

[fixeighted]

If you have Forest then say and I can zip a scene for you

[stelees]

Hey, are you saying if I have Forest Pack? yeh I use forest pack pro for my landscape renders. This one has me completely baffled, I tried for ages after I posted this message.. put all sorts of shapes, grids, trees, even text in the sky to try and break up the light to form god rays - I am REALLY missing something obvious here.

[hermit.crab]

I took a look at your scene and the reason for the lack of god rays is the scene setup. For them to be seen you'll need to 'separate' your beams of light a lot more than with a single thinly latticed plane. This quick tutorial about god rays should shed light on the matter.

[fixeighted]

Unfortunately Max crashed just as I had a reasonable scene setup.
Thanks for adding that link Aleksander, however this is mainly what every tutorial is referring to, an interior, which is far simpler to set up than what the OP wants, which is a classic 'sun through trees' exterior.
This, from my research, is still a really tricky thing to accomplish (for some specific reasons) and unfortunately the realiatic way Vray works makes this sort of thing really artist-unfriendly.
It's been talked about for years but there isn't currently a way to get what we all would like easily, unless I am mistaken.

For an outdoor scene I eventually used a load of trees on a plane, camera mid-way in, sun pointing at the camera, visible, with a sky in the slot.
Then it was basically a LOT of fiddling to try to balance the sun intensity, turbidity, exposure, sun size and trying to block light from the sides/back.
This was using a box gizmo for the fog, as not doing so was just not happening. Also uncheck 'scatter GI'

The problem is that although I 'could' get it to work, it was not right....too faint; the relative intensities were simply wrong and this is the main issue - that Vray, though 'realistic', cannot deal with the range of intensities in a way that is required for a shot like this to work simply.
It has been suggested that an extra function be added allow for multiplying the effect of those rays that are produced - this was back in 2015 iirc from the thread. So hopefully we'll see that one day.
Vlado mentioned that his research stated that even in rl this sort of shot is done with comped separate exposures as these intensities are hard to capture. Not sure how up-to-date that is with the latest cameras...I don't use one.
So, it's doable but a headache....and if you get it to work then don't move the sun whatever you do....it only works from one angle with those settings you've spent 2 hours tweaking

If I am wrong about any of this or am approaching this in an incorrect way then please say

[Undersky]

This, from my research, is still a really tricky thing to accomplish (for some specific reasons) and unfortunately the realiatic way Vray works makes this sort of thing really artist-unfriendly.
It's been talked about for years but there isn't currently a way to get what we all would like easily, unless I am mistaken.

I fully agree. Compared to other render engines (like Redshift) it's still such a hassle to get control over volumetric lighting in V-Ray. If we could just get a kind of "phase" function (like in VrayVolumeScatterMtl) and a way to control contribution on a per light basis, it would be so much easier and quicker to get a good result. It's so un-intuitive to have to create specific lights for the volumetric effect if you, for example, want to have sunlight coming into a window in an interior and in the same time being able to control the interior lights and how they contribute to the volumetric.

[stelees]

Hey, yep agree with what is said here.. godrays at night through a small area like that tutorial can be achieved. and yes also, I am talking about the rays you can see during the day, not in a thick fog but when you are in the woods, sun is shining and there are decent rays visible to the naked eye.

https://pixabay.com/photos/light-for...s-rays-989068/

I too also have tried trees in the scene. Using the pine in Forest pack I have had a row of trees about 400m long @ 200% scale. Then a bit in front another row 150% scale to try and mix up the size and the density, the sun coming down ahead of the camera but sort of shing back at the camera, I have had itto the left of the camera, to the right of the camera. I have tried to have a light just to try and push the rays through the trees and then a sun to light everything else and all while trying to balance out not having a scene so foggy you cannot actually see anything. I have tried ozone in the sun settings and pretty much anything else I could see that may be remotely tied in with atmospherics.

Would love to see a tutorial from Chaos or a base scene to at least start us off in the right direction as this seems like it's a pain point far and wide.

[Karol.Osinski]

Thanks for starting this out, it is very interesting topic :P I recently thought about it as I am working on a renowating and old italian market and I was planning create some god rays getting inside through a roof for the interior shot - I believe it could work very well in this case as this effect can often be seen in the semi-open space markets.

Going back to an issue - in case you guys haven't seen them. Great tut about god rays, in spanish but easy to follow with YT auto subs.

https://youtu.be/TqwPNHIIXgo

[fixeighted]

I just accidentally found this recent post https://forums.chaosgroup.com/forum/...alfog-question

I can't try this as I'm afk but will later on. The responders seem to be convinced this will work just fine and so I'll be intrigued at the results if getting the sun/sky to work is so problematic.

[fixeighted]

Well that thread solved the issue in part. Indeed, using an HDR, in my case https://hdrihaven.com/hdri/download....itou_park&r=8k was an instant success, as in this image.
So I spent hours trying to achieve something only barely close to this with a sun/sky, yet just throwing a random hdr in works beautifully in seconds
It would be cool if sun/sky worked as well but at least there is a workable method otherwise

[stelees]

so this is just a dome light with the HDR image in there, sun and sky turned off - what about the sky map?

[fixeighted]

Yes, only a hdr mapped dome, simple as that. I was pleased yet astonished. Everything is better, the shadows, overall lighting plus ofc the rays you needed to see
I linked to the map I used, which is basically what I imagine the sun/sky to be able to do with ease, as it's a blue clear sky and a bright, pretty sharp sun.

[stelees]

hmmm I assume you jack up the multiplier to get the intensity. I have the HDRI as the environment map (replacing the vray sky). I have the HDRI set with the sun in line with the camera, set to spherical and the sun is turned off not getting the rays. I have a cluster of trees in the way so there should be ample filtering?!

[fixeighted]

Here's a file, simplified for size, so just add whatever trees you like. Specifically I used black pine, distribution 53186.562 with patches 3, just so there is an ideal gap for the sun to come through.
https://www.dropbox.com/s/y1vctccg03...AMPLE.max?dl=0
The thing is you'll notice the intensities are not at all extreme....basically default all and a mult of 2.1 on the HDRI.

[stelees]

Thanks for the file, I'll have a look soon. What I realised is that the godrays were not showing in the preview.. when I did a sample render.. boom there they were.