| Pre_Scene_Return=s | Set pre scene return actions |
| Pre_Frame_Return=s | Set pre frame return actions |
| Post_Scene_Return=s | Set post scene return actions |
| Post_Frame_Return=s | Set post frame return actions |
| User_Abort_Return=s | Set user abort return actions |
| Fatal_Error_Return=s | Set fatal return actions |
Note that no +/- switches are available for these options. They cannot be used from the command line. They may only be used from INI files.
Most operating systems allow application programs to return an error code if something goes wrong. When POV-Ray executes a shell command it can make use of this error code returned from the shell process and take some appropriate action if the code is zero or non-zero. POV-Ray itself returns such codes. It returns 0 for success, 1 for fatal error and 2 for user abort.
The actions are designated by a single letter in the different ..._Return=s options. The possible actions are:
For example if your Pre_Frame_Command calls a program which generates your height field data and that utility fails then it will return a non-zero code. We would probably want POV-Ray to abort as well. The option Pre_Frame_Return=F will cause POV-Ray to do a fatal abort if the Pre_Frame_Command returns a non-zero code.
Sometimes a non-zero code from the external process is a good thing. Suppose you want to test if a frame has already been rendered. You could use the S action to skip this frame if the file is already rendered. Most utilities report an error if the file is not found. For example the command pkzip -V myscene mysce012.tga tells pkzip you want to view the catalog of myscene.zip for the file mysce012.tga. If the file isn't in the archive pkzip returns a non-zero code.
However we want to skip if the file is found. Therefore we need to reverse the action so it skips on zero and doesn't skip on non-zero. To reverse the zero vs. non-zero triggering of an action precede it with a "-" sign (note a "!" will also work since it is used in many programming languages as a negate operator).
Pre_Frame_Return=S will skip if the code shows error (non-zero) and will proceed normally on no error (zero). Pre_Frame_Return=-S will skip if there is no error (zero) and will proceed normally if there is an error (non-zero).
The default for all shells is I which means that the return action is ignored no matter what. POV-Ray simply proceeds with whatever it was doing before the shell command. The other actions depend upon the context. You may want to refer back to the animation loop sequence chart in the previous section. The action for each shell is as follows.
On return from any User_Abort_Command if there is an action triggered and you have specified...
On return from any Fatal_Error_Command proceed with the fatal error no matter what. Exit POV-Ray with error code 1. On return from any Pre_Scene_Command, Pre_Frame_Command, Post_Frame_Command or Post_Scene_Commands if there is an action triggered and you have specified...
On return from a Pre_Scene_Command if there is an action triggered and you have specified...
On return from a Pre_Frame_Command if there is an action triggered and you have specified...
On return from a Post_Frame_Command if there is an action triggered and you have specified...
On return from any Post_Scene_Command if there is an action triggered and you have specified...
Here is a description of each stream.
BANNER: This stream displays the program's sign-on banner, copyright, contributor's list, and some help screens. It cannot be turned off or directed to a file because most of this text is displayed before any options or switches are read. Therefore you cannot use an option or switch to control it. There are switches which display the help screens. They are covered in section "Help Screen Switches".
DEBUG: This stream displays debugging messages. It was primarily designed for developers but this and other streams may also be used by the user to display messages from within their scene files. See section "Text Message Streams" for details on this feature. This stream may be turned off and/or directed to a text file.
FATAL: This stream displays fatal error messages. After displaying this text, POV-Ray will terminate. When the error is a scene parsing error, you may be shown several lines of scene text that leads up to the error. This stream may be turned off and/or directed to a text file.
RENDER: This stream displays information about what options you have specified to render the scene. It includes feedback on all of the major options such as scene name, resolution, animation settings, anti-aliasing and others. This stream may be turned off and/or directed to a text file.
STATISTICS: This stream displays statistics after a frame is rendered. It includes information about the number of rays traced, the length of time of the processing and other information. This stream may be turned off and/or directed to a text file.
STATUS: This stream displays one-line status messages that explain what POV-Ray is doing at the moment. On some systems this stream is displayed on a status line at the bottom of the screen. This stream cannot be directed to a file because there is generally no need to. The text displayed by the Verbose option or +V switch is output to this stream so that part of the status stream may be turned off.
WARNING: This stream displays warning messages during the parsing of scene files and other warnings. Despite the warning, POV-Ray can continue to render the scene. You will be informed if POV-Ray has made any assumptions about your scene so that it can proceed. In general any time you see a warning, you should also assume that this means that future versions of POV-Ray will not allow the warned action. Therefore you should attempt to eliminate warning messages so your scene will be able to run in future versions of POV-Ray. This stream may be turned off and/or directed to a text file.I ignore the code S skip one step A all steps skipped Q quit POV-Ray immediately U generate a user abort in POV-Ray F generate a fatal error in POV-Ray F then turn this user abort into a fatal error. Do the Fatal_Error_Command, if any. Exit POV-Ray with error code 1. S, A, Q, or U then proceed with the user abort. Exit POV-Ray with error code 2. F then generate a fatal error. Do the Fatal_Error_Command, if any. Exit POV-Ray with an error code 1. U then generate a user abort. Do the User_Abort_Command, if any. Exit POV-Ray with an error code 2. Q then quit POV-Ray immediately. Acts as though POV-Ray never really ran. Do no further shells, (not even Post_Scene_Command) and exit POV-Ray with an error code 0. S then skip rendering all frames. Acts as though the scene completed all frames normally. Do not do any Pre_Frame_Command or Post_Frame_Commands. Do the Post_Scene_Command, if any. Exit POV-Ray with error code 0. On the earlier chart this means skip step #4. A then skip all scene activity. Works exactly like Q quit. On the earlier chart this means skip to step #6. S then skip only this frame. Acts as though this frame never existed. Do not do the Post_Frame_Command. Proceed with the next frame. On the earlier chart this means skip steps #4b and #4c but loop back as needed in #4d. A then skip rendering this frame and all remaining frames. Acts as though the scene completed all frames normally. Do not do any further Post_Frame_Commands. Do the Post_Scene_Command, if any. Exit POV-Ray with error code 0. On the earlier chart this means skip the rest of step #4 and proceed at step #5. S then skip rendering all remaining frames. Acts as though the scene completed all frames normally. Do the Post_Scene_Command, if any. Exit POV-Ray with error code 0. On the earlier chart this means skip the rest of step #4 and proceed at step #5. A same as S for this shell command. S or A same as I for this shell command.
Section 6.2.5
Text Output
Section 6.2.5.1
Text Streams
Table Of Contents