Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: micmac on 2016-11-13, 15:36:57

Title: non homogeneous fog
Post by: micmac on 2016-11-13, 15:36:57
Hello,
I try to render a automne scene with fog. I want to achieve a foggy mood but not homogenous...
Is there a way to achieve this affect? The picture attached is just an exemple!
thanks!
Title: Re: non homogeneous fog
Post by: romullus on 2016-11-13, 16:16:35
Not really. But i encourage you to go to this poll and give your vote for non-homogenous volumetric implementation. Currently it's pretty undervoted.
Title: Re: non homogeneous fog
Post by: Fluss on 2016-11-13, 16:17:52
Not really. But i encourage you to go to this poll and give your vote for non-homogenous volumetric implementation. Currently it's pretty undervoted.

Where is it ?
Title: Re: non homogeneous fog
Post by: micmac on 2016-11-13, 16:25:30
https://forum.corona-renderer.com/index.php/topic,96.0.html
Title: Re: non homogeneous fog
Post by: romullus on 2016-11-13, 17:18:29
Yeah, sorry, i forgot to attach link.
Title: Re: non homogeneous fog
Post by: TomG on 2016-11-13, 18:54:47
In the meantime, could render a World Position pass (CGeometry_WorldPosition render element) and use that in, say, Fusion to add 3D fog in post. I have a tutorial about that which ought to be live sometime soon (we've got quite a few tutorials coming out at the moment!)

Thanks!
   Tom
Title: Re: non homogeneous fog
Post by: maru on 2016-11-14, 15:31:22
Yes, there is a way to do this - just use 3ds Max native environment effects (fog, volumetric fog). It can be used to produce really nice results.
Title: Re: non homogeneous fog
Post by: Jpjapers on 2016-11-15, 08:56:26
Can someone explain what is meant by 'non-homogenous' fog?
Title: Re: non homogeneous fog
Post by: romullus on 2016-11-15, 11:09:43
Can someone explain what is meant by 'non-homogenous' fog?

As far as my understanding goes, it's when volumetric properties can be controled by map in all 3 directions, not only in X and Y. I may be very wrong though.

Yes, there is a way to do this - just use 3ds Max native environment effects (fog, volumetric fog). It can be used to produce really nice results.

I always thought that native enviroment effects does the same thing as Corona's volumetrics. Is there substantial difference in their behaviour? Might be worth to give it a try.
Title: Re: non homogeneous fog
Post by: FrostKiwi on 2016-11-15, 11:11:36
Can someone explain what is meant by 'non-homogenous' fog?
Different fog intensities in different volumes.

Basically an Opacity map for your Fog, but in 3D, so you can produce results like in the first photo, without creating a mesh from a fluid sim or similar workarounds.
Title: Re: non homogeneous fog
Post by: pokoy on 2016-11-15, 12:02:45
From my tests the Max fog doesn't get any shading from Corona's lights or environment, it's just a correctly blended illuminating something, but certainly not true volumetric fog. Am I missing something?
Title: Re: non homogeneous fog
Post by: mraw on 2016-11-15, 13:07:10
max's fog can produce really nice results- but under it's hood it is a post-effect, right?
Title: Re: non homogeneous fog
Post by: Jpjapers on 2016-11-15, 13:08:44
Right so you can get the change in density from say the water surface and up on the z axis??
Title: Re: non homogeneous fog
Post by: FrostKiwi on 2016-11-15, 14:27:49
Right so you can get the change in density from say the water surface and up on the z axis??
Check here for V-Ray example. (https://docs.chaosgroup.com/display/VRAY3MAX/Environment+Fog+%7C+VRayEnvironmentFog#EnvironmentFog|VRayEnvironmentFog-fogDistance)
Title: Re: non homogeneous fog
Post by: PROH on 2016-11-15, 15:08:32
..or check here for Corona example (at 45sec):

It works pretty similar as with mr. Which means that it's working best with exposure set to 0. But Rawalanche shows a nice trick in the video: Use a CoronaSky-Map as fog-map. This gives you some control over the brightness of the fog.

Note that it renders slow.
Title: Re: non homogeneous fog
Post by: maru on 2016-11-15, 15:15:21
Yes, there is a way to do this - just use 3ds Max native environment effects (fog, volumetric fog). It can be used to produce really nice results.
I always thought that native enviroment effects does the same thing as Corona's volumetrics. Is there substantial difference in their behaviour? Might be worth to give it a try.
As pokoy and mraw said, it is just a post effect, and it does not get any shading. But it can be sometimes used to create nice aerial perspective.