Table of Contents

This page provides information on rendering with V-Ray GPU.


Overview

Rendering with V-Ray GPU performs the raytracing calculations on the GPU devices installed in the system, rather than the CPU. Since GPUs are specifically designed for massively parallel calculations, they can speed up the rendering process by an order of magnitude.

To enable GPU rendering, go to Render Properties (with the V-Ray Render Engine selected) and set the V-Ray Engine to GPU. See the Choose Which Device to Use for Render section below for more information on device selection.

Additionally, you can enable RTX acceleration for NVIDIA RTX GPUs.

You can use it with both Progressive and Bucket Sampler types.



Supported Hardware and Drivers

V-Ray GPU renders with the NVIDIA CUDA and RTX platforms.

Below is a list of tests we have performed and the results:

  • NVIDIA – When the engine is set to V-Ray GPU (with RTX disabled), the CUDA platform is used. It is supported only in 64-bit builds of V-Ray for Maxwell, Pascal-, Turing- or Volta-based NVIDIA cards. See here if your card has the minimum required computing capability.
  • NVIDIA RTX – When the engine is set to V-Ray GPU with RTX enabled, V-Ray GPU uses the RT Cores in NVIDIA RTX GPUs.
  • Hybrid Rendering (running CUDA on GPU and CPU):  V-Ray GPU CUDA rendering can be performed on CPUs and NVIDIA GPUs at the same time. Using Rendering Devices, you can enable your CPUs as CUDA devices and allow the CUDA code to combine your CPUs and GPUs to utilize all available resources. See the section for more.


V-Ray GPU supports rendering on multiple GPUs. See the sections below on how to choose devices to run V-Ray GPU on.

V-Ray GPU needs compatible GPU device(s) to use for rendering.

When rendering, the output window provides information about your current driver version. If the version is not compatible with the V-Ray GPU, a message with the recommended version is displayed.

The V-Ray GPU page on the Chaos website always lists the latest recommended driver.

To use NVLINK on supported hardware, NVLINK devices must be set to TCC mode. This is recommended for Pascal, Volta, and Turning-based Quadro models. For GeForce RTX cards, an SLI setup is sufficient. Also note that to prevent performance loss, not all data is shared between devices.


Choosing Which Devices to Use for Rendering

You may not want to use all available GPU devices for rendering, especially if you have multiple GPUs and you want to leave one of them free for working on the user interface, or you may want to combine your CPU and GPU together (see the Hybrid Rendering section below). To do this, you can use the supplied GUI tool, which you can find in Start Menu > Programs > Chaos > V-Ray for Blender > Select devices for V-Ray GPU rendering. 





After changing this option, you need to restart Blender (or V-Ray Standalone) if it is running for the changes to take effect. If the V-Ray GPU render server is running as a Windows service, you may need to stop it from the Services applet in the Control Panel.

The Select devices for V-Ray GPU rendering tool also allows for selecting GPU devices for Denoising.

 Note

When multiple devices are selected for denoising, out of all the devices that match the query, only the device with the highest computing capability is used for the denoising process.

The asterisk (*) sign next to a GPU device's name in the list means that a monitor is connected to that GPU device. If two or more monitors are connected to the GPU device, there are 2 or more asterisks next to the GPU device name.

When you hover over the asterisks, a tooltip appears that shows information on the GPU and the number of monitors connected to it.


Hybrid Rendering with CPUs and the CUDA Engine

V-Ray GPU can perform hybrid rendering with the CUDA engine utilizing both the CPU and NVIDIA GPUs. V-Ray can now execute the CUDA source on the CPU as though the CPU was another CUDA device. To enable the hybrid rendering mode, simply enable the C++/CPU device from the list of GPU devices.

The hybrid rendering mode does not require any special drivers. Furthermore, you can use the CPU as a CUDA device even if you don't have an NVIDIA GPU and/or NVIDIA drivers installed. Meaning, this mode can be used on computers that don't even have GPUs. The hybrid render engine running on a CPU supports the same features as the regular V-Ray GPU CUDA engine.


References

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