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Overview

Depending on the scene setup, V-Ray GPU might reach high VRAM consumption due to scene complexity, which might end up with an Out-Of-Mem error. Adding GPU device with more VRAM to the machine is always the best option to resolve the issue. But if that is not acceptable option you may use the following techniques to reduce the amount of VRAM used and eventually render the scene without Out-Of-Mem error.

Using NVlink when hardware

supports it

The latest Nvidia technologies allows stacking Memory Amount from multiple GPU devices together. NVlink technology enables V-Ray to use GPU Memory from all NV-linked GPU devices as a single unit which makes possible rendering much more complex projects without hitting Out-Of-Mem error.

Optimizing textures

V-Ray GPU allows you to apply on-the-fly optimization to the project textures. There are three different texture modes.

Using the GPU device with highest Memory Amount

Although V-Ray GPU is compatible with different GPU models and brands there are certain limitations in terms of Memory usage. If multiple GPU Devices are available, V-Ray GPU is limited by the GPU with the lowest amount of VRAM. 

 If Out-Of-Mem error occurs and your hardware setup consists of GPU devices with different Memory Amount, you may try excluding the GPU devices with less Memory and render the project without them. This way V-Ray will be able to fully utilize their Memory.

Export to .vrscene and render with V-Ray Standalone

Host Applications just like V-Ray need some VRAM to keep the scene open and to operate with it. Depending on scene complexity Host Application may occupy a few gigabytes of VRAM which could be very valuable for V-Ray in case there isn't enough Memory for the Rendering. Exporting the scene to a .vrscene file and Rendering rendering it with V-Ray Standalone will minimize VRAM consumption by excluding the Host Application.

vray -sceneFile="\\path\to\exported\scene.vrscene" -rtEngine=5

As mentioned above, this approach will reduce VRAM usage from the GPU devices connected to monitors.

Using GPU Hybrid Rendering with CPU enabled only

This is not very effective approach in terms of render times since V-Ray won't benefit from using GPU devices. However if the scene is massive and there is no way to fit it into the GPU memory, it is still possible to render it with V-Ray GPU by using Hybrid Rendering with CPU enabled only.

Using V-Ray Proxies

V-Ray Proxies is a very powerful tool which is especially useful for optimizing scenes with a lot of geometry. They are not that Memory Efficient for the GPU rendering as they are for the CPU, but they allow replacing the original geometry in the scene with simplified one. This alone may help reducing VRAM usage from the Host Application leaving more Memory for V-Ray to work with.