You cannot .x3d files to .gif in the usually sense, simply because Xara .x3d files contain instructions (in XML format) about how to render certain 3D model and not bitmap graphics (like GIF). The only way this is doable is, if you render the file using Xara Designer Pro and use the export function to make some kind of preview in GIF format.
Convert X3D graphics model to Graphics interchange file format.
We found one software available in the database for this conversion.
Microsoft Windows software - convert x3d to gif on Windows
A graphics editor, illustration tool and web design from Xara
Convert from x3d file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.