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This page provides some extra tips on rendering a V-Ray Volumetric Grid.

Distributed rendering

A common problem with setting up DR is that the VRayVolumeGrid may look for the cache files in a local machine directory. However, at the start of a network render, the scene file is copied to all render machines on the network to a new location, e.g. C:\Users\user\AppData\Local\backburner\Jobs\, while cache files are not automatically sent to the host machine. The cache files are not sent because on one hand they may be really huge and may overload the disk space of the host, and also because in many cases not all of them are actually used in the rendering. This is why when the rendering begins if the hosts are looking for the cache files in a directory that was originally on the local computer, the cache files won't be found.

The solution is to move the cache sequence to a shared folder on the network, or a mapped network drive, and set its path in the Input panel, using a network-visible UNC input path (a path that starts with \\). You can also browse from the Input panel's path options.

With the Windows operating system, if the path points to a drive on the local computer rather than a UNC path, a message will appear: "You are using local machine Input path with distributed rendering!".

Manually equalizing the render settings with FumeFX

Certain FumeFX settings can be optimized to keep render times as low as possible:

  • Make sure the Step % value matches the corresponding FumeFX step parameter. A smaller Step % value will lead to longer render times.
  • In the Fire rollout, select Fuel as the channel the fire color is based on, as this is FumeFX's Fire channel after importing the .f3d file. For Fire Opacity Mode, choose the Use Own Opacity option and carefully duplicate the fire color and fire opacity diagrams from FumeFX.
  • Please note that VRayVolumeGrid does not support the Fluid Mapping option in FumeFX.
  • VRayVolumeGrid has the option to illuminate the other objects in the scene automatically by using emissive lights. This will increase render times. In order to turn it off and keep only the illumination on the volumetric itself, set the Light Power on Scene value to 0.0 and set Self-shadowing to Grid-based. You can also speed up the calculations of self-illumination by reducing the Light Grid Resolution (%) value.
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