Debugging

This chapter contains some troubleshooting tips for V-Ray and the App SDK.

Error logging

Always watch out for is V-Ray's errors and warnings by implementing the LogMessage callback. In the following example we show how this is done, along with the interpretation of the different log levels:

Python

C++

C#.NET

Node.js

Error checking

Most methods that can fail have at least a boolean return value, so make sure you've checked this when you encounter problems.

Plugin parameters

A very useful tool for basic parameter information is plgparams.exe included in the binary folder of the SDK. It lists all parameters for the specified plugin (or all plugins with -list) and their types, default values and text comments. Similar information can be obtained using the plugin and parameter meta-info API discussed in the Fundamentals section. The ListAllPluginsAndProperties example in the C++ folder (or equivalent code for another language) uses this API.

Parameter information is also available in the comments for the C++ and .Net concrete Plugin classes (as a tooltip in the IDE).

Additional documentation

Apart from documentation included with the App SDK and this self-training program, the help pages for 3dsMax and Maya on docs.chaosgroup.com are a good source of parameter information and examples, although they use names of types and parameters as they are in the UI of the respective application - these are usually similar but different from the underlying V-Ray plugins.

Save scene file for inspection

It is often useful to save out your scene to a file to inspect if you did everything properly. For example you may have failed to set some parameter properly and you will see this in the file as a missing or incorrect value, although you can also check the result of the set operation in your code (when using setValue). You can try to pinpoint problems by deleting parts of the scene file (parameters or whole plugins) and re-rendering.

It can be very helpful if you have a V-Ray for 3dsMax or Maya and use it to export vrscene files to see what plugins and parameters are written out. The exporters for 3dsMax and Maya can be considered "ground truth" (even though they may have an occasional bug or missing feature).

Coordinate system

If you're getting a black render make sure your camera is positioned and oriented properly and not inside an object. Keep in mind the default up-axis is Z, but it can be set to something else, usually Y. You might also get invisible or black objects if something is wrong with the attached material. In this case you can still see the object in the alpha channel if there is nothing behind it - the environment has 0 alpha.

Also keep in mind that V-Ray uses column-major matrices (like OpenGL, but unlike DirectX).