This page provides troubleshooting assistance for general V-Ray problems.


Page Contents

 

Overview


For troubleshooting installation and licensing issues, please check the Installation PDF Guide

If you experience any problems not discussed below while using V-Ray, please contact Chaos Group Support.

 

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 3ds Max. 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.

Crashes with motion blur enabled – A common problem is when there are motion-blurred objects depending on one another; in that case, hiding the original object and using a copy of it for rendering helps.

Using the native 3ds Max Skylight light type – Either on its own, or as a part of the Daylight system. If this is the case, use V-Ray's own environment dialog to create the skylight effect.

Incompatibility with other plugins – If you suspect this is the reason for the error, please contact Chaos Group Support as well as the plugin vendor and explain the situation. Please note that the problem might be in the plugin and not in V-Ray. Some plugins were specifically coded for the default scanline renderer and may behave unpredictably with 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 3ds Max 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 32-bit machines, the Windows® operating system allows by default up to 1.5 GB for any single process (application). That means that even though you may have more physical RAM (for example 2GB), the operating system will not allow an application to use all of that memory.

However, on the Windows® XP operating system, you can change this by using the famous /3GB switch in your boot.ini file. This will enable the OS to allocate up to 3 GB of RAM for any given application. Using that switch may allow you to render your scene without using any of the methods below for reducing memory usage.

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 (reduce Max. levels, increase Min. leaf size, increase Face/level coefficient, switch from Static to Dynamic Default Geometry).

If all else fails, use  Proxy Objects | VRayProxy  objects.

Mapping UVW channels – in 3ds Max, every mapping channel takes up the same or larger amount of RAM as the geometry itself. Unused mapping channels can increase RAM usage dramatically while not affecting the scene in any way. In recent 3ds Max versions, texture channels are generated by default for all objects when they are created. V-Ray has no control over RAM usage for texture coordinates - you will have to make sure that only the channels you need are actually present in the scene. Using  VRayProxy for Optimizing Scenes  objects is also a solution since in that case texture coordinates are also cached to disk along with the actual geometry.

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 3ds Max, V-Ray has no direct control over their memory usage. However, you can use the Bitmap pager settings of 3ds Max to reduce the RAM taken up by bitmaps. For more information, consult your 3ds Max documentation.

Bitmap filtering – Summed area filtering uses much more memory than Pyramidal filtering.

Shadow maps – these may also take up significant amounts of RAM. Again, these are managed by 3ds Max and V-Ray has no direct control over their memory usage. To reduce memory usage, you can switch to raytraced  VRayShadows instead

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:

Use the 3ds Max Bitmap pager, if you are rendering to the 3ds Max default VFB.

If you use V-Ray's own VFB, 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.

Switch to a different image sampler – for example, the Adaptive DMC sampler uses less RAM than the Adaptive subdivision sampler.

Global illumination caches – irradiance maps, photon 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 photon map  – the memory depends on the number of photons stored. You can reduce this number by reducing the Diffuse subdivs for the lights, or by increasing the Max. density.

For the light chache map  – increase the Sample size.

3ds Max scene – 3ds Max 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:

Collapse modifiers to editable meshes

Cache animations with a PointCache modifier

 

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 – f.e. 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.