Click the link if you want to know how to add new templates to the list. (/ousnius/BodySlide-and-Outfit-Studio/wiki/Reference Templates) are defined in the RefTemplates.xml file and point to a specific installed project and shape to load.
To load a conversion reference, choose the File -> Load Reference menu item and select your reference in the template drop down list. One example where this can be made use of, is to convert an outfit from one body type to another (slider value 0% -> 100%). Other meshes loaded into Outfit Studio can be conformed to these sliders, so that they will morph along with the reference shape. The mesh provided with the conversion reference is the reference shape. Outfit Studio comes with so called conversion references, which consist of one or more sliders that can morph a mesh from one shape to another.
