ShortCode in a do_shortcode hook

Hi,
I try to build an automated insertion of an 3d viewer without using shortcode.
This is what i have done :
– inserting the declaration of javascript files in the footer
– adding the do_shortcode hook in the main part of single pages
– adding the mime type dae via the WP Add Mime Types plugin (tried the other method by adding mime type dae in the functions.php file of my theme.
– using the $variable = sprintf(‘[3D … ù1 … %2 ,]method in order to add dynamically the file for displaying.
The string of the uploaded filer appears to be ok (ie, a .dae file). However, when passed through the do_shortcode hook, the name of the file remains, but the extension is changed in png … Thus, the plugin cannot work.
In order to add a file, i use Advanced Custom Fields.
Does someone has an idea of what is happening, and how to get rid of this problem, for example in the functions.php file ?
Thanks in advance
Movihardt