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Check the list of devices in the GPU Devices menu in the Export tab of the V-Ray Renderer node. If you don't see your device on the list there (the list is empty), try to uncheck the In process checkboxthe In process checkbox. This will make V-Ray run as a separate process, working around the limitation. If this does not help as well and you have already updated to the latest drivers, please contact Chaos Group Support.

Why does the UI of my OS

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become sluggish when I use GPU?

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  • If you have multiple GPUs, you can speed up screen refresh time by removing the GPU used for monitor/viewport redraw from the devices that GPU uses for rendering.
  • If you have only one GPU on your system, you could try reducing the value for for Rays per pixel and/or Ray bundle size in V-Ray Renderer node > Renderer > IPR > Performance. This will break up the data passed to the GPU into smaller chunks so that user interface requests can be processed faster. However, this might reduce rendering speed. Enable Show statistics to check the difference in render speed (GPU utilization) and  as well as to help find the optimal settings for your system.
  • The Low thread priority parameter was designed to help with this issue. Turn it on from V-Ray Renderer > Renderer > Options > Rendering.

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Light Cache can be used as secondary GI engine with V-Ray GPU for production rendering. Brute Force is always used as the primary GI engine. In IPR mode, however, Brute Force is always used for primary and secondary GI engine, regardless of the GI engine settings, unless you load your Light Cache from a file. The reason for that is that the Light Cache is view dependent, and recalculating it every time the camera changes its position in IPR doesn't make much sense.

Why do

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some bump maps look different with GPU?

ll procedural Procedural textures are supported for GPU bump maps, but because V-Ray GPU is a very different engine, the bump map itself can look a bit different compared to V-Ray.

Larger scenes cause

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a "Failed to allocate memory for buffer" error with V-Ray IPR GPU. Why?

 If If you get the following error message, this means that some or all of your video cards do not have sufficient memory to load the scene. 

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The difference in render speeds depends on the video cards and the CPUs that are compared, as well as on the scenes used as benchmarks. It is normal to achieve a big speed boost with the GPUs compared to the CPU with some scenes and to have equal performance with others. If you, however, consider that this might be a bug, please contact Chaos Group Support.

Can I use multiple systems with GPU devices to speed up my rendering?

Yes, you can speed up your rendering using DR on multiple systems with CUDA enabled devices.
Keep in mind that if some drivers may have limitations and may not be able to use GPUs if there is no monitor attached to the machine or you are logged in via Remote Desktop (for example). Check the GPU vendor documentation for more information.

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  1. Go to Render View > Render button. V-Ray IPR will start render rendering directly in the Render View.
  2. To render in the VFB, go to V-Ray Renderer > Export > Use V-Ray Frame Buffer. Once enabled, go to Render View and press the Render button.
  3. You can use the Render Region option, if you go to Scene View (viewport).

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Though GPU rendering with CUDA on MacOS devices is no longer supported, the advanced users can bring back the old behavior by using the following environment variable: VRAY_APPSDK_UNHIDE_DEVICES=1 written in houdini.env. 

How can I

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get access to the nightlies section?

If you have registered for V-Ray for Houdini Beta, then you automatically have access to the nightlies section. You can access them here. Note that you have to provide your Chaos Group credentials.

I run Houdini 16.5 Qt 4. Why does V-Ray

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give me an error?

Please note that V-Ray is only supported on on Qt 5 versions of Houdini. If you run into trouble starting up V-Ray for Houdini, please make sure you operate a Qt 5 version of Houdini before contacting us.

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