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Section
The supported features of

Although V-Ray GPU

running on CUDA and RTX are

shares the same

.

Although CUDA and RTX share the same user interface as the V-Ray engine, V-Ray GPU differs from the regular V-Ray engine in the way it performs certain calculations.  Comparing Comparing the results will never come to a one-to-one match, although it may look quite close. Furthermore, it is not the goal for them to be the same.

This is why , it is strongly recommended to not switch between engines in the middle of your project - if you start setting up a scene with the regular V-Ray engine, use it for the entire project.  The The render settings will only show the available options and your scene will be optimized for GPU rendering.

V-Ray GPU can be used as a production render or in interactive mode to quickly preview scene changes. It also supports both the Progressive and Bucket Image Samplers.

To enable GPU rendering, from V-Ray Asset Editor → Settings tab → Render rollout, select  CUDA or RTX select  GPU engine. You can use it with both Progressive and Bucket Sampler types.

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V-Ray offers two rendering engines - V-Ray and V-Ray GPU.

GPU rendering allows V-Ray to perform the raytracing calculations on the GPU cards 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. V-Ray GPU uses NVidia CUDA or RTX device(s) to perform the raytracing calculations. The GPU engine can be specified from the V-Ray GPU rollout.

In addition, you can also use CUDA GPU in combination with your CPU device. This is the so-called Hybrid rendering – when CUDA GPU performs raytracing calculations with the CPU, or simultaneously with both the CPU and GPU devices of your computer.

V-Ray GPU supports a variety of features and even more features are added with time.

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Why V-Ray GPU?

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V-Ray GPU has a number of advantages:

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  • NVIDIA – The CUDA GPU engine is supported only in 64-bit builds of V-Ray for Maxwell and later NVIDIA cards. Rendering on multiple GPUs is also supported. See here if your card has the minimum required compute capability.
  • NVIDIA RTX – Choosing RTX GPU engine mode works with RTX cards.
  • Hybrid Rendering (running CUDA on GPU and CPU): Starting with V-Ray 3.6, V-Ray GPU CUDA rendering can be performed on CPUs and NVIDIA GPUs at the same time. Using the Select Devices for V-Ray GPU Rendering you can enable your CPUs as CUDA GPU devices and allow the CUDA GPU code to combine your CPUs and GPUs to utilize all available resources.

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Тo 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, a SLI setup is sufficient. Also note that to prevent performance loss, not all data is shared between devices.

For more information, see the OptiX and NVLink FAQ page.

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The RTX engine type only works with NVidia RTX cards.


Choosing Which Devices to Use for Rendering

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||V-Ray||> Tools > External > GPU Device Selection

Or find the vray_gpu_device_select.exe file here C:\Program Files\Chaos\V-Ray\V-Ray for Rhinoceros\vrayappsdk\bin.

Note: For versions prior to V-Ray 7, the path is C:\Program Files\Chaos Group\V-Ray\V-Ray for Rhinoceros\vrayappsdk\bin.

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||V-Ray Asset Editor|| > Settings > Render > GPU device list dropdown

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If you see your CPU listed twice, choose the option with "C++/CPU " in the name.


Hybrid Rendering with CPUs and the

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GPU Engine

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Starting in 3.60, V-Ray GPU can perform hybrid rendering with the CUDA GPU engine utilizing both the CPU and NVIDIA GPUs. V-Ray can now execute the CUDA GPU source on the CPU, as though the CPU was another CUDA GPU device. To enable the hybrid rendering mode, simply enable the the C++/CPU device device from the list of CUDA devicesGPU devices. You can specify whether the GPU engine uses CUDA or RTX cards.

The hybrid rendering mode does not require any special drivers. Furthermore, you can use the CPU as a CUDA GPU 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 as the regular V-Ray GPU CUDA engine.

More info about the nature of Hybrid rendering is available at the blog post Understanding V-Ray Hybrid rendering.

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