Scene troubleshooting

This article covers information on how to troubleshoot a scene and determine the cause of its issue. 

Overview

While working on a project, you may have stumbled upon something that prevents its progress. This could be artifacts, slow rendering, hanging, large memory consumption, crashing, incorrect or unexpected render results. Such issues are generally caused by something within the scene. 

For example: 

In order to find a solution, it’s necessary to isolate the culprit and deal with it properly.

Since a scene usually contains hundreds of objects, this process may not be as easy as it sounds. It’s important to streamline the troubleshooting method to quickly narrow down the problematic area of the scene. 

Adjust settings for faster rendering

Scene debugging requires a lot of re-renderings. To speed up this process it’s important to tweak the scene to render as quickly as possible. Use the following options  to speed up the rendering:

Reset the V-Ray render settings

Resetting the V-Ray settings to their defaults is probably the easiest way to determine whether the issue lies in the global settings. Oftentimes parameters are wrongly interpreted or exaggerated. 

A quick and effective step to save troubleshooting time is to restore the Default Render Settings.

Learn how in our article about Resetting the V-Ray Render Settings.

Comparе the current Render Settings with the defaults

If resetting the V-Ray render settings resolves the issue, the next step is to find which particular parameter/s caused the issue. To find out, the previous and current render settings should be compared. 

This can be done in several ways:

• Compare Render Settings Using the Technical Documentation

The Default Render Settings are displayed as screenshots on their relevant page in the Chaos Documentation. Use the values as a comparison reference.

• Compare Render Settings Using a .vrscene File

  You can manually compare the render settings of several scenes via export to a .vrscene file. To check the differences in the render settings, compare the troublesome scene with a default (empty) scene. Text editors like Notepad++ (with the Compare plugin) could be used for this purpose. 

  Here's a step-by-step guide:

  1. Export the original scene to .vrscene file.

  2. Export a new empty scene to a .vrscene file.

     Here's how:

     • 3ds Max
     • Maya
     • SketchUp
     • Rhino
     • Revit
     • Cinema 4D
     • Houdini
     • Blender
  3. Open both files into a text editor and start the Comparing mode.

  4. Look for sections starting with Settings

     For example:

     SettingsOutput vraySettingsOutput {

     SettingsOptions vraySettingsOptions { 

     SettingsImageSampler vraySettingsImageSampler {

     

     5. By comparing both .vrscenes you could quickly find the differences between the parameters. These are the potential suspects.

     6. To find out if a specific parameter causes the issue, restore it to its default value and render the scene.

      

• Compare Render Settings in the V-Ray Frame Buffer (3ds Max)

  You can compare the current render settings to the render settings of an image stored in the History. It can be used to quickly compare the scene's Render Settings with the Defaults. 

  To do that:

  1. Render the scene with the original settings
  2. Save the output in the VFB History
  3. Reset the Render Settings
  4. Right-click on the image in the History window and select Compare V-Ray Settings
  5. A new window pops up and displays the current scene's settings with the ones saved in the image.

V-Ray scene converter (3ds Max)

V-Ray for 3ds Max includes a V-Ray scene convert tool for converting non-V-Ray objects, such as materials or cameras to V-Ray ones. Run it with all the checkboxes enabled.

More information about the V-Ray scene converter.

Override all materials

Another method for narrowing down the cause of an issue is overriding the scene materials with a default V-Ray material. If the issue is resolved by doing so, it means it lies in the scene shading.

Learn how in our article on How to globally override scene materials in V-Ray.

Once the problematic Material/Map is found, it could be replaced with a similar material or it could be recreated from scratch. The troubleshooting process could dive deeper by going through the parameters of the problematic Material but in most cases, this is not needed.

Troubleshoot geometry

If the issue is not found in the render settings or materials, it could be caused by the geometry. The possible origin could be:

To find the corrupt geometry, start deleting parts of the scene until the issue stops reproducing. If you have lots of geometry in the scene, delete the objects that are not in the view first. Afterward, begin removing the visible ones half by half, rendering after each removal, until you find the culprit.

Troubleshoot lights

You can quickly test whether the lights are causing issues by disabling all of them and creating a dome light or a directional light instead. This should give you good overall lighting of the scene, which serves as a good basis for comparison and/or drawing conclusions. 

If the issue is with a specific light, you have to track it down and start testing with it. Render elements such as Diffuse, Refraction, Reflection, and Specular can tell with which part of the output image the light is have problems.

Fast pre-check

Conclusion

If you can't determine what is going on with your scene, please contact us. Send us a report of all your findings, screenshots or/and videos of the issue. If it is scene-specific, send us the scene (preferably stripped for quicker troubleshooting) along with the assets.

Contact Chaos Support.