### 2.4.7 Miscellaneous questions

#### 2.4.7.1 Where do I suggest new features?

"I would like to suggest some new features for the program. Who should I talk to?"

This is best discussed on the Pov news groups (news.povray.org) in both the general news group and the windows news group. The Pov team does skim through the message posted there and occasionaly impliment ideas that have been posted by users.

You may also contact any of the POV-Ray T.A.G. members with suggestions, comments, or ideas for improvements to POV-Ray. You can learn more about the POV-Ray T.A.G. and their contact information on the TAG web page.

#### 2.4.7.2 I'm getting a "Illegal grid value in dda_traversal()"

"When I render a height field I get lots of warning messages saying "Illegal grid value in dda_traversal()". How can I correct that?"

(Answer by Jerry Anning)

Basically, you have a ray going "between the cracks" of the height field due to an arithmetic accuracy problem. Sometimes it does no harm. Sometime you get black dot or line artifacts. I know of no successful patch so far. I also know no completely reliable workaround. The best bet is to slightly joggle the camera position and/or angle.

#### 2.4.7.3 No beep when finished?

"How can I get rid of the beep after POV-Ray has calculated the image"

Usually using the `-P` command-line option should help (POV-Ray will not pause after it has calculated the image). If you are using the windows version of POV-Ray, you can try Render -> On Completion -> Remove [v] in front of "Beep".

#### 2.4.7.4 POV-Ray viruses?

"Are there any POV-Ray viruses out there? Can one be done?"

At the time of writing this documentation, no known viruses or trojans made with the POV-Ray Scene Description Language (SDL) are known to exist.

Due to the properties of the POV-Ray SDL, writing a working virus (that is, a piece of code which spreads, without the user knowing, by copying itself to non-infected files) is very difficult, if not impossible to do. The main obstacle in making a POV-Ray virus is that there is no way for the SDL code to reside in memory, infecting files when it sees them; another problem is that there is no way to get file listings in the POV-Ray SDL, so the code cannot infect other .pov files at parse time.

However, trojans (i.e. a malicious piece of code which attempts to harm the system, but will not infect other files) are much more likely. It is possible with the POV-Ray SDL to open a file and write practically anything to it. This can be used to cause severe damage to an unprotected file system.

Note, however, that in POV-Ray 3.5 the concept of I/O restrictions was introduced in order to protect the user from these kinds of malicious scripts. Setting the I/O restrictions properly will prevent the SDL from being able to open files for writing (and optionally even for reading). You should check that your copy of POV-Ray 3.5 has these restrictions properly set, especially if you render files not made by you. Note, however, that not all versions of POV-Ray 3.5 for different platforms may have these restrictions implemented. Consult section 1 of the POV-Ray 3.5 documentation for more details about the I/O restrictions.

Regardless of this, it is always a good idea to run only scripts which you have received from trusted sources. This is particularly true if you are using a version of POV-Ray older than 3.5.

The POV-Ray community consists mostly of benevolent people and it is generally safe to try POV-Ray scripts made by them. However, it is often better to be safe than to be sorry.

#### 2.4.7.5 GUI for Unix POV-Ray?

"Does POV-Ray for Unix have a GUI like in Windows?"

No.

POV-Ray has always been a command-line utility. Even the core code of POV-Ray for Windows is exactly the same as the generic command-line POV-Ray. The graphical interfaces of the Windows and Mac versions of POV-Ray are exclusive to them (and non-portable). They are much like separate "add-ons".

There is no official GUI done for the Unix version of POV-Ray. Some third-parties have tried to make some GUIs for it (and you might find them in the links collection on our website) but it seems to be a general phenomenon that Unix people like to use just the command-line version with a proper and powerful text editor (such as Emacs).

I am sorry but there is no advice right now here about how to configure Emacs in order to smoothly handle POV-Ray file editing, but I might write a page about that some day, when I have the time.