Usually solving problems with MTL file is simple – just install proper software and open the file. Read the guide and open MTL file now!
A 3D graphic file with the extension .MTL stores material configuration data, saved in text format, including texture bitmap file names and their arrangement on a three-dimensional model saved in a parallel .OBJ file.
There could be multiple reasons for which the system does not support given file. In the case of MTL extension, it is probable that none of the installed programs support given file type. Therefore, user should undertake the following steps
If an application that supports MTL files is installed on user’s system, but is not used to open such files by default, right-click on the file icon and choose "Open with" option from the menu. Next, select the proper application and check the "Always use the selected application to open this kind of files" box. The system will store this information in its registry and use the selected program to open files with MTL extension by default.
For Mac OS users the procedure is analogous – open the file menu by right-clicking on the MTL file and choose "Information" option and select "Open with program" option. From the submenu select an application and click on "Change all" button.
Inability to open MTL files may also be related to the lack of any application that supports given file being installed on the system. Should that be the case, user needs to download and install one of the following applications. Once installed, the system will automatically associate newly installed application with MTL files. If this step fails, see step 1.
Sometimes, although relatively rarely, steps 1 and 2 might not lead to expected results. There can be several reasons for such situation to occur: