Clouds with Vray Env Fog

[Daytona]

Hi there,

I am trying to do an animation with small fluffy cumulus clouds like this:

This suppose to be a time lapse animation during sunset and for the sky/sun I was so far going with the standard VraySun.
I was thinking of doing the clouds with a pflow as the Vray Env Fog gizmo with shape instance objects with a couple of simple variations of the fluffy clouds.
First of all I was getting an error (unhandled exception ... ) and had to go with mesher compound object as my gizmo, but that's not such a big issue. I could just as well scatter a couple of those geometry elements and animate them by hand.
Second thing is that I can't seem to get the right amount of detail in the clouds. It tends to look pretty blurry, despite the fact I use the max level of iterations in the procedural maps and no matter how high I go with the subdivs in the EnvFog settings. Obviously there's a point where decreasing the step size makes the render ridiculously slow, but still no clear effect in the renders. Looking at the examples here
it looks like it shouldn't be such a problem. Not sure what I'm doing wrong.


Here's what I've got so far:


So far I haven't found a way to make it more dense at the 'core' of each cloudlet. Using radial gradient map overlayed with the base noise map didn't work too good as well as some other variations with fallof maps (which don't seem to be taken into account at all). Maybe if there was a way to use the UV map channel of the gizmo it would work better.

I was planning on using the Env Fog for a few projects, including some galaxy/star dust and smoke puffs in a huge explosion. But to do that I would really need to find a way to make the effect more crisp.

My last question is about animating the clouds. If I move them how will the noise pattern behave? Will it move along with the geometry or stay in place with the world coordinates? It would be great if they had some small amount of 'evolution' in place, just like the real clouds do, but still should move along with the base geometry.

The cloudlets are more or less 300-500 units in length and here are my settings used for the render:

Fog distance - 15
Scatter bounces - 50
subdivs - 8
step size - 5 (went as low as 1 with no visible improvement)
texture samples - 8
max steps - 1000
fallof (per gizmo) - 40

[vlado]

You will need to decrease the fog distance - this will make the clouds more dense and their boundaries will be better defined.

Best regards,
Vlado

[Daytona]

Thanks for the quick reply. Decreasing the fog distance makes the gizmo boundaries more visible and trying to offset that with the gizmo falloff makes it look almost identical to the larger fog distance result. The silhouette of the cloud is blurry. I tried to use a smaller gizmo inside the ones I'm using now, but the GI calculation took very, very long. The idea was to make the core denser with larger noise and the outer gizmo less dense with smaller noise and detail (and smaller step size). It looks pretty nice, but as I said the render times make it not really an option for me. I'll guess I have to keep on experimenting.

By the way what's the reason for the errors with pflow? It either crashes and I get an UNHANDLED EXCEPTION: Updating atmospheric effects, or the whole scene renders with the fog all over, like there's no gizmo. :/

There's also one thing that really puzzled me after reading the help section on EnvFog, how do you get this result:


quote: The volumetric textures (density and emission) for this example are provided from a fluid dynamics simulation in the form of 3d textures.

What's the workflow for this one ? Is the fluid dynamics in question done with Phoenix, or is that something done purely inside Max's pflow and how do you output a 3d map from it?

[instinct]

I assume the help file should be updated to reflect this was done with phoenix (which was undisclosed back then if i recall right).

So yes this was done with phoenix. After simulating you can use the phoenix texmap in an environment fog slot to render the simulation instead of using Phoenix' own rendering.

Regards,
Thorsten