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Creating clouds with VRayEnvironmentFog

Tutorial by Francesco Legrenzi

One of the most interesting features introduced in V-Ray 1.5 SP3 was VRayEnvironmentFog (VEF). It might look like a simple fog system, similar to the one in 3ds Max, but it's really more powerful. In fact it can interact with Global Illumination and generate volume caustic effects.

Fig. 01 - Example of VEF used for creating fog and haze effect. Image by rendering.ru

VRayEnvironmentFog can generate both lights and volume caustic effects.

Fig. 02 - Lights and volume caustic effects.

Adding a light fog, VEF can be used in interiors to give a mysterious charm.

Fig. 03 - Example of interior fog.

One maybe unexpected implementation is that it allows for creating clouds.



Fig. 04 - 05 - Two examples of clouds using VEF.

Tutorial - Clouds with VEF

Our first step is creating an atmospheric gizmo containing volume effect, and to create a VRayPhysicalCamera, a VRaySun+Sky system and set LWF (Linear Work Flow), in a metric scale scene. The last step makes it easier to handle large scenes.

Fig. 06 - Creating gizmo for VEF.

Create the gizmo with Create-> Helpers-> Atmospherics -> Box Gizmo and setting volume for a cloud layer: 6000x6000x300 meters. Next step: VRayPhysicalCamera.

Fig. 07 - All default params used, eccept reducted focal lenght, to achieve a grandangular emphasizing sky effect. Put in scene as shown to increase perspective look.

Creating light system is quite easy. go to Create -> Lights -> VRay -> VRaySun, dropping light in scene. check yes to popup question to get automatically VRaySky map in 3dsmax Environment.

Fig. 08 - Use default VRaySun params. Take a look at VRaySky map included in Environment map slot, and further selection in VEF.

Now in 3ds max "Environment and effects" module (press "8") we add VEF effect. Following default params:

Fig. 09 - The VEF.
1st rollout, General parameters, manages main effect params.
2nd modulates some features with maps. We're getting clouds adding map to density slot.
3rd rollout links VEF to the related gizmo, that can be shaded by user-defined lights. Step one: link VEF to gizmo.


Fig. 10 - Click Add to select gizmo from scene..

Resulting render. not our best!

Fig. 11 - Not our best.

Enlarge view

Fig. 12 - The gizmo is full of fog.

We see gizmo is "full" of dark and dense fog, so light cannot penetrate it.
Adding texture to density channel we can modulate density areas. Use Noise map with following params:

Fig. 13 - Noise params used for clouds

Following final render parameters:

Fig. 14 - Params for VEF appearance and quality. Thanks to three slots, we meet great flexibility.

More than the other parameters, step size affects render times. Increasing this value decreases render times, trading off render quality.
The final render:

Fig. 14 - Final render.

Conclusion

With a small VRayEnvironmentFog tutorial we introduce an easy and quick way to create a cloud system, able to interact and dynamically react to existing lighting, giving user a powerful tool to create complex and realistic environments. Changing procedural map params and sun or camera position we can also create animations.

Below you'll find som short videos made during beta testing.

Thanks for watching :)



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Francesco Legrenzi is the author of “V-Ray The Complete Guide”. He also runs Legrenzi Studio near Bergamo, Italy.

www.francescolegrenzi.com

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