My system locks up and freezes while rendering

This is most likely a hardware problem. V-Ray cannot cause a system freeze by itself. The worst that V-Ray can do is crash Rhino. Check your memory chips and/or your CPU temperature.

 I get an "unhandled exception" message window while rendering

 The exact text in the message box may differ, depending on where in V-Ray the error occurred. There are different reasons for this message to appear:

Insufficient RAM – One of the most common reasons for the unhandled exception. See the section on Excessive memory usage below for more details.

CPU overheating or RAM defects – This is another reason for unhandled exceptions that has become quite common recently with the increased clock speed of modern processors. It is characterized by random crashes during rendering and may be quite difficult to distinguish from a software problem. Installing a CPU temperature monitoring software and checking the RAM for defects may help to determine whether the problem is in the hardware or the software.

Incompatibility with other plugins – If you suspect this is the reason for the error, please write to Chaos Group Support and to the plugin vendor and explain the situation. Please note that the problem might be in the plugin and not in V-Ray.

A bug in V-Ray – If you believe that this is the problem, try to isolate it (if it occurs in a specific situation related to a certain object, material, atmospheric effect etc.) and email the file c:\vraylog.txt as well as the Rhino scene to Chaos Group Support.

 Excessive memory usage while rendering

Like every other program, V-Ray needs a certain amount of RAM to render an image. Depending on the scene complexity and the render settings, V-Ray will use varying amounts of RAM. Sometimes, the available system RAM may be less than the amount needed for rendering. In this case, you will most likely get an unhandled exception. Check the memory usage from the Windows Task Manager.

On 64-bit platforms, the 64-bit version of the Windows® operating system allows the usage of all available physical memory without limitations.

If you cannot use any of these methods to allow more RAM for rendering, the only choice is to reduce the amount that is needed by changing your scene and your V-Ray settings. The scene elements that take up most of the RAM while rendering can be divided into the following groups:

Geometry – Scenes with lots of objects and/or triangle counts require more memory to render. There are several ways to reduce this amount:

Adjust the raycaster settings in the System rollout.

If all else fails, use V-Ray Proxy | VRayProxy objects.

Displacement mapping – Objects displaced with the 2D displacement mapping method may require a lot of RAM to render, especially with large displacement maps. If this is the case, use the 3D displacement mapping method. Also, if you have several distinct displacement modifiers with the same displacement map, it is better to replace them with one modifier, and apply it to all the necessary objects. This is because each modifier will take RAM for the displacement map separately from other modifiers, even if they have the same map.

Bitmaps – These tend to take up large amounts of RAM, especially if the maps are large. Since textures are managed by V-Ray, you can potentially reduce the RAM usage by lowering the quality of the bitmap textures you are using.

Image buffer – Large output resolutions require a significant amount of RAM to store the final image. Additional G-Buffer channels increase that amount. There are several ways to reduce this amount: 

When rendering in V-Ray, use the Render to V-Ray raw image file option and then use the V-Ray raw image file viewer to convert the resulting file to a different format.

Render the image in several different passes and stitch the pieces in a compositing program.

Image samplers (AA) – The image sampling algorithms of V-Ray require some amount of RAM to hold all the data for the sampled image. This amount can be quite large, depending on the chosen bucket size and sampling rate. To reduce that amount, reduce the bucket size in the Raytrace rollout.

Global illumination caches – Irradiance maps and light maps all require additional memory to store them. Each of these has different methods for controlling its memory usage:

For the irradiance map, the memory depends on the number of samples in the map; you can reduce this number by using lower Min/Max rate, and more loose threshold values (higher Color threshold, higher Normal threshold, lower Distance threshold).

For the light cache map, increase the Sample size.

Rhino scene – Rhino itself stores a lot of information about the scene. V-Ray has no control over that memory, but here are some things you can do to reduce it:

Purge your scene of unnecessary geometry by navigating to Window > Model Info > Statistics > Purge Unused. This will eliminate any unused geometry, materials, styles, and layers from your scene.

 I get splotches in my render when using irradiance map

 There may be several reasons for splotches when rendering with the irradiance map:

 Regular noisy splotches – These are usually a result of insufficient Hemispheric subdivisions for the irradiance map. Usually they appear in difficult lighting situations when the default setting is too low. Examples of difficult lighting conditions are small bright sources of indirect light, hdri environments etc. You can avoid these splotches in several ways:

If you are using brute force GI for secondary GI bounces, try using another method such as the light cache.

Increase the Hemispheric subdivisions for the irradiance map.

Isolated bright splotches – There may be different causes for these:

GI caustics – If you have reflective or refractive surfaces in your scene, especially if they are glossy, V-Ray may try to compute the GI caustics for these surfaces. Since caustics usually require a lot of sampling to get right, there may be splotches.

Incorrect or missing UVW coordinates – If some objects in your scene lack UVW coordinates, or the UVW coordinates fall outside the texture map, this can produce splotches or weird colors in the irradiance map. The solution would be to apply correct UVW coordinates to those objects.

 Where can I download material files?

You can access our material library by signing into the Chaos Group site here:
http://chaosgroup.com/en/2/downloads.html?s=v-ray-materials

 Does V-Ray for Rhino support GPU rendering?

At this time V-Ray does use the video card or the GPU when rendering.

 Which hardware works best with V-Ray?

At this point rendering is all about number crunching. This means that a powerful processor is the best place to focus when choosing a machine. Chaos Group does not recommend any specific brand or endorse a particular model computer, processor or otherwise.

 How can I locate the records of my other Chaos Group purchases?

 Contact Chaos Group Support with as much information as you have about the purchases and we will be glad to locate the records in our system.