POV-Ray is a free ray-tracer. The POV-Ray plugin defines an export of a 3D scene to POV-Ray's file format, this can be used to obtain high-quality images of scenes modelled with GroIMP.

POV-Ray is available for download at http://www.povray.org. For GroIMP's POV-Ray plugin, you need POV-Ray version 3.5 or higher. Please follow the instructions given at POV-Ray's web page in order to install POV-Ray properly.

Note: Most Linux distributions contain POV-Ray. Just select it in the setup tool of your distribution, POV-Ray will then be installed automatically.

If the POV-Ray executable file is named povray and is contained in one of the directories specified in the PATH-variable of your system, no further configuration of GroIMP is necessary. This is the case for most UNIX-like systems, but normally not for Windows systems.

Figure 1: Configuration of the POV-Ray plugin

The configuration of the POV-Ray plugin is done in the Preferences panel, see Figure 1. In the field “Programme”, enter the path to POV-Ray's executable file. For Windows systems, this is typically “C:\Path to POV-Ray Installation\bin\pvengine.exe”. The field “Command line” allows you to specify some options for POV-Ray, which may, e.g., influence rendering quality; please consult POV-Ray's documentation. Finally, the option “Use standard output” controls how the rendered image is transferred from POV-Ray to GroIMP: If POV-Ray's standard output is used, the image is transferred continuously, so that a progressive display within GroIMP is possible. Without standard output, POV-Ray writes its output to a temporary file, which is displayed at once after completion of the ray-tracing process. Generally, the method using standard output is preferable; however, there is a bug in (some versions of) POV-Ray for Windows, which corrupts image data in the output. If you see unexpected colors in the rendered image, deactivate this option.

Note: POV-Ray for Windows is equipped with a graphical user interface for editing POV-Ray scenes etc. Unfortunately, this graphical user interface is always shown, even when POV-Ray is only used in batch mode, as is the case for GroIMP. Depending on POV-Ray's configuration, POV-Ray may even keep running after the rendering has completed. If this is the case, add the option /exit in the field “Command line”. The option /nr keeps POV-Ray from restoring previous edit sessions, which may reduce startup time.

GroIMP's POV-Ray plugin is used in two ways: At first, it defines an export to POV-Ray's file format. This is available via View/Export in the 3D view. You have to specify a file name for the output, the POV-Ray scene will then be written to this file. Some scenes contain additional image files, they will be written into a subdirectory called scene.pov-files (where <filename>scene.pov</filename> is the file name you have chosen).

Secondly, this export is used to obtain a POV-Ray-rendered image of the current scene directly in GroIMP's 3D view. Just use the menu Render View/POV-Ray in the 3D view.

3D geometry and 3D materials are complex objects. Therefore, a 1:1 translation of one representation of 3D scenes to another is almost always impossible. All of GroIMP's geometry can be exported to POV-Ray, however, some objects like NURBS surfaces have to be exported as triangle meshes because POV-Ray does not support them directly. This leads to quite big POV-Ray file sizes.

The export of GroIMP's materials to POV-Ray is even more restricted. For some material definitions, it is not possible to export all of their parts to POV-Ray, so POV-Ray's output may look different from what you would expect. Manual postprocessing of exported POV-Ray-scenes may be necessary.