3D Studio Max can export its project to several file types, including the common JPEG bitmap picture. This will make a static image no longer useable for 3D editing purposes.
Convert Project file to JPEG bitmap image format.
We have found 3 software records in our database eligible for .prj to .jpg file format conversion.
Microsoft Windows software - convert prj to jpg on Windows
A widely-used 3D animation application from Autodesk
Convert from prj file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned prj to jpg. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A graphics design tool for making 3D landscaping and animations
Apple macOS / Mac OS X software - convert prj to jpg on OS X
3D modeling and animation package for Mac.