Multiple fog layers / instances - best practice ?

[Dmerc]

How would you handle multiple, overlapping fog instances?

Use case example: large terrain, HDR lighting, with some general atmosphere + dense clouds (could be either Environment fog with gizmo or Volume Grid)

I could each one just fine with a separate vray environment fog - but 2 environment fog instances don't work properly, right?

What is a "clean" approach?

Thank you in advance,
Peter, xoio

[hermit.crab]

For what you described as a scenario, creating two fog instances, one confined in gizmos for your clouds and another for atmosphere should work properly. The position in the list does matter, so make sure the gizmos fog is on top so it can overlap properly.

[Dmerc]

Hello Aleksandr - thank you for coming back to me ...

I tried both variations, but it's not really there. I attached some renders. Obviously the dense fog is better on top - still then the denser fog is completely unaffected by the haze of the other, which is not "correct". You can see it in the second red block which is quite further away ...

I know, it is probably quite complicated to render, but in the end you should have two atmospheric effects also affecting each other.

Additionally since atmospherics affect the Z-Buffer it's also complicated to do it in the post.

Any additional ideas?

[hermit.crab]

They do affect each other, but possibly not the way you would like. You can try replacing the general fog with the 'VRayAerialPerspecitve' effect to get the atmospheric perspective effect you described.

[Dmerc]

Hey Aleksandar,
Tried it, but I kind of remembered that Aerial Perspective is meant to be used with Sun/Sky - it doesn't consider HDRs. Either way, the issue is completely the same. Is there any way to have atmospheric effects properly overlap / penetrate? Or is the native "stacking" system of 3ds-Max the issue?

Or is there any way to assign a volume shader material to an object / would that make a difference? (That's how I know it from a different engine, but I really would love to use Vray for this ...).

Thank you for your consideration!

Peter

[hermit.crab]

Another thing you can do is create the clouds with the VRayVolumeGrid (no cache required). Add an empty VolumeGrid (cancel when prompted to browse for cache), open the Volumetric Options (Rendering tab), change the Smoke Opacity to be based on 'Smoke' and click 'Modulate' to choose a texture. To control the thickness of the smoke, use the curve (left point upwards will make the smoke denser). You can control the color from the Smoke Color tab.

[olika]

Hi Peter,

just discovered your post.
For the hdri aerial perspective thing, i have something,
you can create a sun and place it where the hdri sun is and then turn it off.
Aerial perspektive is then still taking the sun into account altough it's turned off and then it's working with a hdri setup